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MEMS-based micropumps in drug delivery and biomedical applications
Abstract
This paper briefly overviews progress on the development of MEMS-based micropumps and their applications in drug delivery and other biomedical applications such as micrototal analysis systems (μTAS) or lab-on-a-chip and point of care testing systems (POCT). The focus of the review is to present key features of micropumps such as actuation methods, working principles, construction, fabrication methods, performance parameters and their medical applications. Micropumps have been categorized as mechanical or non-mechanical based on the method by which actuation energy is obtained to drive fluid flow. The survey attempts to provide a comprehensive reference for researchers working on design and development of MEMS-based micropumps and a source for those outside the field who wish to select the best available micropump for a specific drug delivery or biomedical application. Micropumps for transdermal insulin delivery, artificial sphincter prosthesis, antithrombogenic micropumps for blood transportation, micropump for injection of glucose for diabetes patients and administration of neurotransmitters to neurons and micropumps for chemical and biological sensing have been reported. Various performance parameters such as flow rate, pressure generated and size of the micropump have been compared to facilitate selection of appropriate micropump for a particular application. Electrowetting, electrochemical and ion conductive polymer film (ICPF) actuator micropumps appear to be the most promising ones which provide adequate flow rates at very low applied voltage. Electroosmotic micropumps consume high voltages but exhibit high pressures and are intended for applications where compactness in terms of small size is required along with high-pressure generation. Bimetallic and electrostatic micropumps are smaller in size but exhibit high self-pumping frequency and further research on their design could improve their performance. Micropumps based on piezoelectric actuation require relatively high-applied voltage but exhibit high flow rates and have grown to be the dominant type of micropumps in drug delivery systems and other biomedical applications. Although a lot of progress has been made in micropump research and performance of micropumps has been continuously increasing, there is still a need to incorporate various categories of micropumps in practical drug delivery and biomedical devices and this will continue to provide a substantial stimulus for micropump research and development in future.
... This pumping capability is the foundation of many microfluidic systems such as inkjet, chemical micro-reactors, and lab-on-a-chip devices. Previously, many types of pumps have been developed to perform pumping in micro-systems [7] and pump technologies continue to be developed. ...
... The challenging problem of microscale pumping has been approached in a number of ways. A wide variety of micropumps have been used including active and passive pumping schemes [7][8][9][10][11][12]. While these pumps are effective for pumping in specific circumstances, general disadvantages of these pumps are moving parts, complicated geometries, large sizes, and difficulty in fabrication or constraints on the fluid properties. ...
The paper describes a novel concept for a low cost microfluidic platform utilizing materials and processes used in low cost thermal inkjet printing. The concept re-purposes the jetting elements to create pumps, mixers, and valves all necessary components for the transport of fluids in a broad range of microfluidic applications.
... As an example, we report a simulation concerning a MEMS drug pumping device subjected to an V in the shape of a square wave, whose amplitude is equal to 48V (considering that, for simplicity of calculation, V s ¼ 100V), while the frequency is fixed at 25 Hz (Nisar, 2008). Therefore, as shown in Figure 8(a), in dimensionless conditions, jmax Vj ¼ 0.48 and the period is equal to 0.04. ...
... To the choice of the aforementioned V, for reasons of implementation simplicity, we associate constant d ¼ 0.2 [as required by many industrial applications ] to simulate effects due to E ff independent on both x and t (Nisar, 2008). Therefore, l is also of the same shape and at the same frequency but with an amplitude, in dimensionless conditions, of 0.22, as illustrated in Figure 8(b). ...
Purpose
Based on previous results of the existence, uniqueness, and regularity conditions for a continuous dynamic model for a parallel-plate electrostatic micro-electron-mechanical-systems with the fringing field, the purpose of this paper concerns a Galerkin-FEM procedure for deformable element deflection recovery. The deflection profiles are reconstructed by assigning the dielectric properties of the moving element. Furthermore, the device’s use conditions and the deformable element’s mechanical stresses are presented and discussed.
Design/methodology/approach
The Galerkin-FEM approach is based on weighted residuals, where the integrals appearing in the solution equation have been solved using the Crank–Nicolson algorithm.
Findings
Based on the connection between the fringing field and the electrostatic force, the proposed approach reconstructs the deflection of the deformable element, satisfying the conditions of existence, uniqueness and regularity. The influence of the electromechanical properties of the deformable plate on the method has also been considered and evaluated.
Research limitations/implications
The developed analytical model focused on a rectangular geometry.
Practical implications
The device studied is suitable for industrial and biomedical applications.
Originality/value
This paper proposed numerical approach characterized by low CPU time enables the creation of virtual prototypes that can be analyzed with significant cost reduction and increased productivity.
... Some of these transport mechanisms inspired the design of pumps for microfuidic systems which may be used for biological and chemical sensing, drug delivery, molecular separation, amplification, and sequencing [7]. There are two major classes of such pumps: mechanical displacement pumps, which apply forces to fluids via moving boundaries, and electro-and magnetokinetic pumps which provide energy to fluids continuously and as a result generate flow [8]. ...
Recent experiments proposed to use confined bacteria in order to generate flows near surfaces. We develop a mathematical and a computational model of this fluid transport using a linear superposition of fundamental flow singularities. The rotation of a helical bacterial flagellum induces both a force and a torque on the surrounding fluid, both of which lead to a net flow along the surface. The combined flow is in general directed at an angle to the axis of the flagellar filament. The optimal pumping is thus achieved when bacteria are tilted with respect to the direction in which one wants to move the fluid, in good agreement with experimental results. We further investigate the optimal helical shapes to be used as micropumps near surfaces and show that bacterial flagella are nearly optimal, a result which could be relevant to the expansion of bacterial swarms.
... Electromechanical control in MEMS combines mechanical and electrical parts to create compact, efficient devices for automotive safety and various industries [89][90][91]. Microtechnology enhances drug delivery efficiency, especially to challenging areas, using methods like microneedles. ...
The convergence of microelectromechanical systems (MEMS) and nanomaterials is transforming healthcare by enabling breakthroughs in diagnostics, drug delivery, and biosensing. This synergistic integration offers unprecedented precision, miniaturization, and biocompatibility, overcoming critical challenges in detecting disease markers and delivering therapies. MEMS-based devices, when combined with nanomaterials, achieve heightened sensitivity and specificity, allowing for early diagnosis and targeted treatments across various medical applications. From cancer detection to neurotransmitter monitoring for mental health management, this fusion holds immense potential in advancing personalized medicine. As research in this domain continues to evolve, MEMS-nanomaterial technologies are poised to significantly enhance healthcare outcomes by improving diagnostic accuracy, treatment efficacy, and patient well-being. This review discusses recent advances, key challenges, and future perspectives on the role of MEMS and nanotechnology in shaping the future of healthcare innovation.
... Electrostatic actuation is a leading mechanism in micro/nanoelectromechanical systems (MEMS/NEMS), chosen for its numerous advantages. This method has spurred the development of various electrostatic actuators employed in applications such as micro/nanomotors, switches, relays, resonators, mirrors, pumps, valves, and filters [10,27,35,42,52,121,124,149,150,160,194,218]. [220] categorizes these devices by: ...
The focus of this work is on the dynamics of a particle/particles escape from a potential well. This problem is crucial in describing various physical, chemical, and biological processes. The phenomenon of escape finds relevance in numerous examples, such as the capsize of ships due to external excitation by waves, where the analysis of simplified ship dynamics can provide approximate criteria for capsize.
The escape phenomenon also plays a crucial role in the gravitational collapse of stars and has applications in physics and engineering, notably in the Josephson effect and dynamic buckling, an essential aspect of elastic instability phenomena. In the realm of micro-electromechanical systems (MEMS), the study of escape dynamics aids in improving devices like MEMS switches, and in the context of particle absorption and trapping, it is instrumental in the use of moving mirrors and electromagnetic traps for both charged and neutral particles. Further examples include polymer escape in chemistry and energy harvesting using bi-stable potential wells.
The theoretical aspect of this study includes investigations into escape dynamics governed by differential equations with initial conditions. Dependence on these initial conditions, coupled with excitation parameters such as frequency, amplitude, and phase shift, determines whether escape occurs. This binary outcome of escape or non-escape depends on the multidimensional space of parameters and initial conditions. In addition to detailing the binary escape set, it may also be useful to determine the escape rate, i.e., the time required for a particle to exit the potential.
The study also considers the role of damping in systems, noting its presence in normal-sized applications such as ship capsizing, its absence in atomic and celestial-sized processes, and the complexity it adds in moderately damped systems. This complexity arises from the inability to disregard damping entirely or rely solely on stationary motion, given the significance of transients in escape phenomena.
The transient nature of escape, which occurs only once, presents challenges in detection, requiring precise analytical solutions (or at least estimates) to determine the conditions for escape.
In essence, this thesis delves into the fundamental mechanisms of escape, particularly focusing on the example of the harmonic oscillator with and without viscous damping. It extends to investigate the escape dynamics of coupled particles and explores the potential of utilizing escape for the control of particles within a sinusoidal potential well. Additionally, the study introduces mathematical theorems related to averaging and global optimization of periodic functions, providing valuable tools to address problems related to escape dynamics. These elements collectively shape the core of this research, reflecting a focused yet comprehensive exploration into the multifaceted realm of escape dynamics.
... The magnet or coils adhere to the membrane. When current travels through the coils, the generated magnetic field generates attraction or repulsion between the coils and the permanent magnet, thereby providing the actuation force (Nisar at al 2008). A solenoid, an electromagnet formed by the cumulative overlapping of magnetic field lines in loops, is used in an actuator to attract a membrane. ...
The influence of gravity plays a crucial role in micropumps’ fluid dynamics. Gravitational forces have an intricate effect on the fluid flow of the micropump. Understanding gravity’s influence on micropump fluid dynamics is critical for improving the fine design features and operational efficacy of the microscale pumping systems. This study conducted thorough a numerical analysis on the Single Inlet Double Outlet Diaphragm (SIDOD) micropump and the Double Inlet Single Outlet Diaphragm (DISOD) micropump to determine how gravity influences the performance. In this research, the optimal frequency is identified as 3 Hz. At this frequency, the SIDOD flow rate increases from 313 μl min⁻¹ without gravity to 327.77 μl min⁻¹ with gravity, marking an increase of 4.77%. Similarly, the DISOD flow rate rises from 177.78 μl min⁻¹ without gravity to 184 μl min⁻¹ with gravity, reflecting an approximate 3.56% increase. A comprehensive understanding of gravity impact is crucial for aerospace applications, where micropumps may operate under fluctuating gravitational conditions. The potential applications of micropumps in medical devices, particularly drug delivery systems, experience gravitational variations.
... Electrostatic actuation is the most popular actuation mechanism used in micro/nanoelectromechanical systems (MEMS/NEMS) due to its many inherent advantages that make it ideal to use as a (NEMS) such as micro/nanomotors, micro/nanoswitches, micro/nanorelays, micro/nanoresonators, micromirrors, micropumps, microvalves, and micro/ nanofilters [1][2][3][4][5][6][7]. Electrostatic MEMS/NEMS benefits from the relatively intensive coupling between different energy domains at micro-and nanoscale levels. ...
Presented herein is a comprehensive investigation on the nonlinear vibration behavior of nanoplate-based nano electromechanical systems (NEMS) under hydrostatic and electrostatic actuations based on nonlocal elasticity and Gurtin-Murdoch theory. Using nonlinear strain-displacement relations, the geometrical nonlinearity is modeled. Based on Kelvin-Voigt model, the influence of the viscoelastic coefficient is also discussed. Nonlocal plate theory and Hamilton’s principle are utilized for deriving the governing equations. Furthermore, the differential quadrature method (DQM) is employed to compute the nonlinear frequency. In addition, pull-in voltage and hydrostatic pressure are considered by comparing the results obtained from nanoplates made of two different materials including aluminum (Al) and silicon (Si). Finally, the influences of important parameters including the small scale, thickness of the nanoplate, center gap and Winkler coefficient in the actuated nanoplate are thoroughly studied. The plots for the ratio of nonlinear-to-linear frequencies against thickness, maximum transverse amplitude and non-dimensional center gap of nanoplate are also presented.
... The transfer and pumping of minute volumes of biological fluids in the order of a few microliters per minute has proven to be an ongoing challenge. Valveless pumps are the preferred choice in microfluidic systems because they can handle biological material gently and have a low risk of clogging (Singhal et al 2004, Woias 2005, Nisar et al 2008, Kawun et al 2016, Mohith et al 2019. Micropumps are employed in a variety of professions, especially biomedicine, where they facilitate fluid handling in Lab-on-Chip systems for drug administration (Liu et al 2022). ...
Microfluidic systems are crucial in various fields including biological fluid handling and microelectronic cooling. Micropumps play a vital role in microfluidics. Valveless micropumps are the preferred choice in microfluidics because of their ability to minimize the risk of clogging and gently handle biological materials. In this comprehensive Four-Flap Valveless Micropump (FFVM) simulation, the fluid flow and associated deformation in the valveless micropump are analyzed. The oscillatory fluid motion generated by a straightforward reciprocating pumping mechanism is transformed into a unidirectional net flow by the micropump. This pump eliminates the need for intricate actuation mechanisms found in valve-based pumps while offering precise direction control. The input is given in terms of the Reynolds number or inflow velocity. In this study, the Reynolds numbers were changed from 16 to 50, which resulted in a positive correlation with the net flow rates, yielding a maximum net flow rate of 20.81 μl min⁻¹ at a Reynolds number of 50. The influence of the average flow velocity is evident, with a peak net flow rate of 29.16 μl min⁻¹ at 50 cm s⁻¹. The FFVM showcases adaptability by delivering fluid within microfluidic pathways, holding promising applications in precision drug delivery systems.
... The final step is boding where the two substrates are bound together by anodic or fusion bonding [30]. The use of MEMS has led to the development of microfluidics which is a field of the design and development of miniature devices that can sense, pump, mix, monitor and control flow of small volumes of fluids [31]. ...
... Microneedles are employed for transdermal drug delivery, facilitating the transfer of molecules through micro-scale skin punctures [38]. Among micropumps, reciprocating micropumps are more widely used and can be actuated through various mechanisms, such as piezoelectric, thermal, magnetic, and electrostatic methods [39][40][41][42]. Some micropumps utilize diffusers/nozzles instead of check valves, earning them the label of "valveless diffusers" or "fixed valve micropumps" [43]. ...
Microfluidic sensors have garnered significant attention over the past decade due to the growing need for microsystem automation and their applications in biology and optical control. This review paper explores the extensive use of microfluidic applications across diverse sectors, including medical, optical, and automation. The study examines various types of microfluidic sensors tailored for specific applications and analyzes the materials employed in microfluidic chips, including their respective advantages and disadvantages. Additionally, it delves into specific microfluidic pressure sensors, elucidating their underlying principles and methods for detecting parameters. This paper explores the concept of microfluidics sensing mechanisms with biomedical applications, flow sensor application to measure the pressure of a fluid, thermal sensor application to measure the cell temperature, and chemical sensor application to measure the concentration of chemicals such as glucose and cocaine. This material is utilized to design the sensor and fabricate the device to measure the fluid properties and effect of fluid in the channel. The paper also explores the need for microfluidic pressure sensors in different categories of applications. In conclusion, the research highlights the existing research gaps within the realm of microfluidic sensors.
... Most recently, microfluidic chips have also found use for several of these technologies [77]. Microtechnology enables the administration of a wide variety of medications [78,79], with excellent therapeutic efficiency, by providing miniaturization, integrations of numerous functions [80,81], and electromechanical control [82][83][84]. High therapeutic effectiveness medication delivery is made possible by microtechnology. In addition, targeted drug delivery to difficult-to-reach parts of our bodies is made possible by microtechnology through alternate delivery methods. ...
... Most reported works on micropumps nowadays study liquid as the operating medium, [1][2][3][4][5][6] while the development of gas micropumps is lagging behind. 7,8 The primary reasons are gas compressibility, sealing challenges, and small actuation forces/amplitudes achievable in the micro domains. ...
The concept of microscale fluidic pump based on microchannel with surface acoustic waves (SAWs), propagating along one of its walls, has been extensively studied in the last decade with possible application to lab-on-chip projects. Meanwhile, any mentions of the application of such device to gas medium seem absent in the literature. The present paper aims to fill this gap by investigating the possibility of using microchannel with SAWs as a microscale gas pump. The numerical study is performed using the modification of the direct simulation Monte Carlo method. It was shown that the pumping effect occurs mainly in the area covered by SAW, while the upper layers of gas are almost still in average. The pumping effect demonstrates weak dependence on gas rarefaction, decreases with the SAW speed, and is lower for a low amplitude to channel height ratios. Finally, it is shown that the propulsion intensity in the open system decreases with a decreasing microchannel height, while the compression ratio in the closed system, on the contrary, increases.
... Microfluidic technology is used to control or sense fluids or their parameters inside the microchannel. Micropumps [11], micromixers [12] and microvalves [13] are miniaturized components of a microfluidic system, and further advancements in microfluidics technology design a microfluidic system that includes all microfluidics components. Microfluidics technology has grown extensively, and further development of microfluidics systems requires additional external components or integrating devices [14]. ...
The demand for microfluidic pressure sensors is ever-increasing in various industries due to their crucial role in controlling fluid pressure within microchannels. While syringe pump setups have been traditionally used to regulate fluid pressure in microfluidic devices, they often result in larger setups that increase the cost of the device. To address this challenge and miniaturize the syringe pump setup, the researcher introduced integrated T-microcantilever-based microfluidic devices. In these devices, microcantilevers are incorporated, and their deflections correlate with the microchannel's pressure. When the relative pressure of fluid (plasma) changes, the T-microcantilever deflects, and the extent of this deflection provides information on fluid pressure within the microchannel. In this work, finite element method (FEM) based simulation was carried out to investigate the role of material, and geometric parameters of the cantilever, and the fluid viscosity on the pressure sensing capability of the T-microcantilever integrated microfluidic channel. The T-microcantilever achieves a maximum deflection of 127 µm at a 5000 µm/s velocity for Young’s modulus(E) of 360 kPa of PDMS by employing a hinged structure. On the other hand, a minimum deflection of 4.05 x 10-5 µm was attained at 5000 µm/s for Young’s modulus of 1 TPa for silicon. The maximum deflected angle of the T-cantilever is 20.46o for a 360 kPa Young’s modulus while the minimum deflection angle of the T-cantilever is measured at 13.77o for 900 KPa at a fluid velocity of 5000 µm/s. The T-cantilever functions as a built-in microchannel that gauges the fluid pressure within the microchannel. The peak pressure, set at 8.86 Pa on the surface of the cantilever leads to a maximum deflection of 0.096 µm (approximately 1 µm) in the T-cantilever at a 1:1 velocity ratio. An optimized microfluidic device embedded with microchannels can optimize fluid pressure in a microchannel support cell separation.
... MSM materials are particularly promising for use in micro-magneto-mechanical systems (MAMS) [5] due to their large magnetic-field-induced strains. Examples of potential applications include high-speed actuators [6], micro fluidic pumps [7,8], mechanical dampeners [9], and energy harvesters [10]. ...
Ni-Mn-Ga-based magnetic shape memory (MSM) alloy microactuators have a high potential in miniaturized devices for which conventional mechanisms or materials are no longer feasible. However, manufacturing single-crystal-based Ni-Mn-Ga micro actuators is challenging due to their high brittleness, which precludes conventional machining methods. The present work introduces and develops a novel manufacturing method-femto-second pulse width laser (FPWL) ablation micromachining-for the manufacture of a functional actuators from oriented Ni-Mn-Ga single crystals. Notably, using a green laser (wavelength 515 nm) permits micromachining in the martensitic phase due to the low heating effect of the process. Optimized FPWL parameters are here used to machine a functional actuator from a five-layered modulated (10 M) martensite Ni-Mn-Ga single crystal. The actuator develops a fully reversible and repeatable magnetic-field-induced strain of 6.5% without any post-processing.
... At present, syringe pumps account for the most popular fluid drivers, but are not suitable for applications outside laboratories due to their bulky sizes and inconvenient power supplies [23,24]. Thus, small-size, lightweight, low-power-consumption micropumps are conceptually required for fluid manipulation in these portable systems and have attracted great interest [25][26][27]. To date, numerous micropumps based on different principles have been developed, such as thermopneumatic [28], piezoelectric [29][30][31][32][33][34][35][36][37][38][39][40][41], electromagnetic [42][43][44][45], phase-change [46], dielectric elastomer [47], electroosmotic [48], electrohydrodynamic [49], and acoustic [23,[50][51][52][53][54][55] systems. ...
Miniaturization of health care, biomedical, and chemical systems is highly desirable for developing point-of-care testing (POCT) technologies. In system miniaturization, micropumps represent one of the major bottlenecks due to their undesirable pumping performance at such small sizes. Here, we developed a microelectromechanical system fabricated acoustic micropump based on an ultrahigh-frequency bulk acoustic wave resonator. The concept of an inner-boundary-confined acoustic jet was introduced to facilitate unidirectional flow. Benefitting from the high resonant frequency and confined acoustic streaming, the micropump reaches 32.620 kPa/cm³ (pressure/size) and 11.800 ml/min∙cm³ (flow rate/size), showing a 2-order-of-magnitude improvement in the energy transduction efficiency compared with the existing acoustic micropumps. As a proof of concept, the micropump was constructed as a wearable and wirelessly powered integrated drug delivery system with a size of only 9×9×9 mm³ and a weight of 1.16 g. It was demonstrated for ocular disease treatment through animal experimentation and a human pilot test. With superior pumping performance, miniaturized pump size, ultralow power consumption, and complementary metal–oxide–semiconductor compatibility, we expect it to be readily applied to various POCT applications including clinical diagnosis, prognosis, and drug delivery systems.
... In recent times, the Microelectromechanical Systems (MEMS) field has made significant contributions to various scientific disciplines, including engineering, physics, medicine, biology, and more. Within these advancements, the field of microfluidics has emerged, focusing on manipulating fluid flow at the microscale within channels [1]. Micropumps play an indispensable role in facilitating the flow of fluids through microchannels. ...
... Since fine-grained randomly structured Ni-Mn-Ga polycrystal contains grain boundaries that can greatly impede twin boundary motion, large MFIS is almost solely found in oriented single crystals [4][5][6]. Properties of MSM alloys make them attractive for use in High-speed actuators [7], microfluid pumps [8,9], mechanical dampeners [10], and energy harvesters [11]. ...
Ni-Mn-Ga-based magnetic shape memory (MSM) alloy single crystals are known for their large magnetic-field-induced strain (MFIS). This quality makes them a promising material for use in micro actuators and devices. However, the manufacturing of single-crystal-based Ni-Mn-Ga micro actuators is challenging due to their high brittleness and other material properties – numerous machining techniques that are successfully used for the deep engraving of conventional engineering materials cannot be directly applied to Ni-Mn-Ga-based alloys. Nevertheless, previous studies have shown that a femtosecond pulse width laser (FPWL) can be successfully utilized for the defect-free micromachining various materials. This work studies the effects of different engraving parameters and introduces a novel scanning-based method for the deep micromachining of Ni-Mn-Ga-based MSM alloys with maximum surface quality. Results show that a 4-layer strategy with a 0.01 mm hatch distance provides excellent machining in terms of surface quality and dimensional accuracy. This study can be utilized within design stages to estimate minimum margin based on required machined depth and avoid defects that occur in the sample preparation stage. Additionally, evolution of structures generated by FPWL machining are characterized. The results highlight how FPWL can be considered a highly capable process for the micromachining and surface structuring of Ni-Mn-Ga-based single crystals for manufacturing multifunctional MSM microdevices.
... Controlling mass transportation enables a wide range of applications, [1][2][3][4][5][6][7][8] such as the design and fabrication of nanoelectromechanical systems, [9][10][11][12][13] particle separation, [14,15] drug delivery, [16,17] and energy conversion. [18,19] There are many ways to control mass transportation, such as the simplest transmission method of gravity, the impact of channels geometric, [20] and defects [21] on water transport behavior, phonon induction that causes the movement of water nanodroplets [22] and external excitation that causes impact response. ...
Controlling mass transportation using intrinsic mechanisms is a challenging topic in nanotechnology. Herein, we employ molecular dynamics simulations to investigate the mass transport inside carbon nanotubes with temperature gradients, specifically the effects of adding a static carbon hoop to the outside of a CNT on the transport of a nanomotor inside the CNT. We reveal that the underlying mechanism is the uneven potential energy created by the hoops, i.e., the hoop outside the CNT forms potential energy barriers or wells that affect mass transport inside the CNT. This fundamental control of directional mass transportation may lead to promising routes for nanoscale actuation and energy conversion.
... Piezoelectric blowers or pumps do not have rotating parts as usual in classical blowers/pumps/fans. It consists of a chamber, valves, and an oscillating diaphragm, which reduces the wear and fatigue damage (as there is no moving part) and also reduces power consumption [25]. The device has a few merits such as high power density, compactness, less noise, and no electromagnetic interaction. ...
... Mechanical pumps bridge the floor range gap between nanomechanical pumps and classical microscale pumps, which ranges between the several micro-litre to several ml per minute. The macron size in this range has a surface-to-volume ratio that is significantly greater than that in microscale, which results in high-viscus forces and restricts down scaling of well-known mechanical pump principles [87][88][89]. ...
Microelectromechanical systems (MEMS) are a technology that allows engineers to create small, integrated devices with electrical and mechanical components to perform tasks carried out by macroscopic systems. MEMS devices are interfaces of the digital world (computer) and the analog world (our surroundings) with the capability of sensing and controlling. System-integrated chip technology is used to make these devices. The main advantages of MEMS are lightweight, ease of fabrication, reduced size, low-power operation, and the possibility of electrical and electronic device interaction. These MEMS devices find applications in biomedical fields such as detection, analysis, diagnosis, therapeutics, drug delivery, cell culture, microsurgery, and genome synthesis. This review paper discusses recent MEMS research, emphasising biomedical applications and advances. This paper includes functional components, technologies involved in manufacturing, and current trends in Bio-MEMS devices. This study discusses the Bio-MEMS device’s accuracy, design problems, prospective applications, and new possibilities.
... Important applications in chemical and biological sensing, including gases, vapors, ions, and various bioanalytes [6][7][8][9][10], are also possible. MEMS sensors have also been utilized for performing air flow measurements that are very important for a large variety of industrial and medical applications [11,12]. MEMS flow sensors are typically based on a heated filament and are called thermal flow sensors, which measure the fluid flow sensor by detecting changes in temperature caused by the flow of the fluid. ...
This paper investigates an AlGaN/GaN triangular microcantilever with a heated apex for airflow detection utilizing a very simple two-terminal sensor configuration. Thermal microscope images were used to verify that the apex region of the microcantilever reached significantly higher temperatures than other parts under applied voltage bias. The sensor response was found to vary linearly with airflow rate when tested over a range of airflow varying from 16 to 2000 sccm. The noise-limited flow volume measurement yielded ~4 sccm resolution, while the velocity resolution was found to be 0.241 cm/s, which is one of the best reported so far for thermal sensors. The sensor was able to operate at a very low power consumption level of ~5 mW, which is one of the lowest reported for these types of sensors. The intrinsic response time of the sensor was estimated to be on the order of a few ms, limited by its thermal properties. Overall, the microcantilever sensor, with its simple geometry and measurement configurations, was found to exhibit attractive performance metrics useful for various sensing applications.
... OEIPs operate based on the concept of using an external electric field to transfer ions or molecules via a permselective ion exchange membrane (IEM). Other existing technologies such microfluidic and microelectromechanical systems (MEMS) based micropumps [85], iontophoresis [86], [87] and organic electronic redox-mediated controlled release [88], [89], falls short as they often distribute larger doses of molecules (in liquid phase) with less control, which could result in unwanted side effects. Convection enhanced delivery (CED) is another drug delivery option that has been used in recent times for treating diseases such as Parkinson's, Alzheimer's, and glioma [90]- [92]. ...
In recent years, there has been significant interest in the use of alternating current electrothermal (ACET) flow in microfluidics due to its ease of use and ability to provide precise results. This research aims to examine the effect of various parameters on the ACET pumping of fluid within microchannels. These parameters include electrode pair sizes (both wide and narrow), channel height, gap between electrode pairs, applied voltage, and the number of electrode pairs in a microchannel. Numerical simulations are conducted to achieve these objectives, and experimental tests are carried out to validate the numerical results. The Design Expert software is utilized to optimize and reduce the number of simulation runs, which are performed using a newly developed ACET solver in OpenFOAM. Furthermore, a global correlation is derived between the outlet ACET flow velocity and the other parameters involved in the problem. Additionally, an ACET test device is constructed to experimentally validate the accuracy of the results obtained by a novel developed solver in OpenFOAM. The results indicate that for microchannels with the desired dimensions, the maximum flow velocity agrees well with the numerical solution in the same region. It is observed that increasing the gap between small and large electrodes by three times reduces the flow velocity by 40 %, while increasing the size of the small electrode by four times reduces the flow velocity by 288 %. Moreover, increasing the height of the microchannel up to a certain amount leads to a 40 % increase in the flow velocity, beyond which the flow velocity remains almost constant.
Microfluidics, the science and technology of manipulating fluids in microscale channels, offers numerous advantages, such as low energy consumption, compact device size, precise control, fast reaction, and enhanced portability. These benefits have led to applications in biomedical assays, disease diagnostics, drug discovery, neuroscience, and so on. Fluid flow within microfluidic channels is typically in the laminar flow region, which is characterized by low Reynolds numbers but brings the challenge of efficient mixing of fluids. Periodic flows are time‐dependent fluid flows, featuring repetitive patterns that can significantly improve fluid mixing and extend the effective length of microchannels for submicron and nanoparticle manipulation. Besides, periodic flow is crucial in organ‐on‐a‐chip (OoC) for accurately modeling physiological processes, advancing disease understanding, drug development, and personalized medicine. Various techniques for generating periodic flows have been reported, including syringe pumps, peristalsis, and actuation based on electric, magnetic, acoustic, mechanical, pneumatic, and fluidic forces, yet comprehensive reviews on this topic remain limited. This paper aims to provide a comprehensive review of periodic flows in microfluidics, from fundamental mechanisms to generation techniques and applications. The challenges and future perspectives are also discussed to exploit the potential of periodic flows in microfluidics.
Light-triggered micro/nano drug delivery systems represent a remarkable advancement in the field of targeted drug delivery. These systems harness the unique properties of light to achieve precise spatiotemporal control over drug release, enabling enhanced therapeutic outcomes and minimizing undesirable side effects. The core principle of light-triggered drug delivery involves the incorporation of photosensitive materials, such as photo-responsive polymers, nanoparticles (NPs), or liposomes, into carrier systems that encapsulate therapeutic agents. These materials possess the ability to undergo reversible structural changes in response to specific wavelengths of light. By carefully designing the carrier systems and selecting appropriate light sources, researchers can achieve on-demand drug release at targeted sites within the body with exceptional precision. This approach offers numerous benefits, including the potential to overcome biological barriers, reduce systemic toxicity, and improve patient compliance. Moreover, the versatility of light-responsive materials allows for the development of tailored drug delivery strategies, ranging from continuous release to pulsatile or even remotely triggered release profiles. Photon energy has the potential to facilitate the creation, connection, breakdown, and heating of materials, contingent on deliberately designed electronic structures and photon attributes. A promising method for treating diverse infections and ailments involves the gentle administration of healing substances without causing harm. Additionally, the wide-ranging possibilities in this field could involve the utilization of machine learning and gene-editing approaches to bolster the intelligence of nano delivery systems.
Low-velocity shock wave-induced contraction and expansion of nanobubbles can be applied to biocarriers and microfluidic systems. Although experiments have been conducted to study the application effects, the dynamic behavior characteristics of nanobubbles remain unexplored. In this work, we utilize molecular dynamics (MD) simulations to investigate the dynamic behavior characteristics of nanobubbles influenced by low-velocity shock waves in a liquid argon system. The DBSCAN (Density-Based Spatial Clustering of Applications with Noise) machine learning method is used to calculate the equivalent radius of nanobubbles. Two statistical methods are then utilized to predict the time series changes in the equivalent radius of nanobubbles without rebound shock waves. The piston velocity is analyzed using the bisection method to obtain the critical impact states of the nanobubble. The results show that at the low velocity shock wave (piston velocity of 0.1 km s-1), the shock wave pressure is small, the non-vacuum nanobubbles contract and expand in a circular shape, and the gas particles inside the bubble are not dispersed. In contrast, the vacuum nanobubbles collapse directly. As the shock wave rebounds upon impact, it triggers periodic contraction and expansion of the nanobubbles. The predictions indicate that the equivalent radius will vary within a small range according to the pre-predicted values in the absence of the rebound shock wave. Nanobubbles are present in four critical impact states: dispersed gaps, multiple smaller bubbles, two split bubbles, and a concave bubble.
On‐demand controlled drug delivery is essential for the treatment of a wide range of chronic diseases. As the drug is released at the time when required, its efficacy is boosted and the side effects are minimized. However, so far, drug delivery devices often rely on the passive diffusion process for a sustained release, which is slow and uncontrollable. Herein, a miniaturized microfluidic device for wirelessly controlled ultrafast active drug delivery is presented, driven by an oscillating solid–liquid interface. The oscillation generates acoustic streaming in the drug reservoir, which opens an elastic valve to deliver the drug. High‐speed microscopy reveals the fast response of the valve on the order of 1 ms, which is more than three orders of magnitude faster than the start‐of‐the‐art. The amount of the released drug exhibits a linear relationship with the working time and the electric power applied to the ultrasonic resonator. The trigger of the release is wirelessly controlled via a magnetic field, and the system shows stable output in a continuous experiment for two weeks. The integrated system shows great promise as a long‐term controlled drug delivery implant for chronic diseases.
The operational stability of radial journal bearings is the bottleneck that limits the reliability of hydraulic suspension micro-pump. Due to self-excited vibrations, the whirl amplitude of the plain journal bearing (PJB) is large at high rotational speeds, which will accelerate wear failure. It has been proven that employing herringbone grooved journal bearing (HGJB) is an effective method to reduce the whirl amplitude and improve operational stability. However, enhancing the stability of journal bearings in micro-pumps by herringbone grooved structures has rarely been studied, and its effect needs to be verified. We validated the mechanism of the stability improvement with the CFD method and compared the dynamic characteristics of HGJB and PJB by rotor dynamics evaluation and experiment. The experimental results show that under the same conditions the whirl amplitude of the HGJB decreases by 29.61% in the x direction and by 24.09% in the y direction compared with that of the PJB. This study reveals the effect of the herringbone grooved structure on the operational stability of bearings and may provide guidance for the reliability improvement of hydraulic suspension micro-pump.
Nanoneedles (NN) are growing rapidly as a means of navigating biological membranes and delivering therapeutics intracellularly. Nanoneedle arrays (NNA) are among the most potential resources to achieve therapeutic effects by administration of drugs through the skin. Although this is based on well-established approaches, its implementations are rapidly developing as an important pharmaceutical and biological research phenomenon. This study intends to provide a broad overview of current NNA research, with an emphasis on existing approaches, applications, and types of compounds released by these systems. A nanoneedle-based delivery device with great spatial and temporal accuracy, minimal interference, and low toxicity could transfer biomolecules into living organisms. Due to its vast potential, NN has been widely used as a capable transportation system of many therapeutic active substances, from cancer therapy, vaccine delivery, cosmetics, and bio-sensing nanocarrier drugs to genes. The use of nanoneedles for drug delivery offers new opportunities for the rapid, targeted, and exact administration of biomolecules into cell membranes for high-resolution research of biological systems, and it can treat a wide range of biological challenges. As a result, the literature has analyzed existing patents to emphasize the status of NNA in biological applications.
Electrostatically-driven microelectromechanical systems (MEMS) devices are mathematically modelled using one dimensional approximation to study the nonlinear dynamics of the resonators. It is observed that the electrostatic fringing field affects the pull dynamics of MEMS resonators. The existing fringing field models are developed under assumption of infinitely wide rigid grounded beam as compared to the deformable beam. These models considered parameters which depends upon the thickness and the width of the elastic beam. In general, the MEMS resonators which are used for practical applications cannot have infinitely wide rigid grounded beam. In this work, a new fringing field model is developed to take into the account the finite width of the rigid beam electrode. A new parameter which accounts the fringing field effect due to the finite width of deformable and grounded rigid beam electrodes is introduced. The performance of the new fringing field model is compared with the existing fringing models for different cases. It is observed that the new fringing field model performance better for all test cases.
Molecularly rigid polymers with internal charges (positive charges induced by amine methylation) allow electroosmotic water flow to be tuned by adjusting the charge density (the degree of methylation). Here, a microporous polyamine (PIM-EA-TB) is methylated to give a molecularly rigid anion conductor. The electroosmotic drag coefficient (the number of water molecules transported per anion) is shown to increase with a lower degree of methylation. Net water transport (without charge flow) in a coupled anionic diode circuit is demonstrated based on combining low and high electroosmotic drag coefficient materials. The AC-electricity-driven net process offers water transport (or transport of other neutral species, e.g., drugs) with net zero ion transport and without driver electrode side reactions.
Micropumps are regarded as essential components which provide power for fluids or gas in microfluidic systems, and require high flow-rate performance, versatility, miniaturization, and integration for applications. This paper presents a novel microfluidic device which features an easily-integrable high-performance electromagnetic micropump with bio-inspired gears synchronous check valves. The micropump includes a silicon microchannel, magnetic piston, one or two electromagnetic actuators, and two pairs of bio-inspired geared synchronous valves which open and close subject to pressure differences. Two micropumps with different drive modes—that is, mono and dual drive mode—and volumes—namely, 0.51 cm3 and 0.62 cm3—were fabricated and tested using a bi-directional pulse power supply under different frequency and current conditions. The proposed device achieved maximum net flow rate of 1913.24 μL/min in deionized water and a flow-rate volume ratio of 3.09 mL min−1 cm−3 in opened test system and showed great potential of pumping in closed fluid circuit with different resistances. The bio-inspired valve has two synchronous sub-valves to reach higher response and opening, and the valve synchronization ratio of sub-valves was more than 90 %. The test was conducted for working fluids of different types and viscosities, highlighting its versatility. Overall, this micropump with bio-inspired valves and miniaturized actuators combined with its high-performance flow rate and working-fluid versatility—demonstrated its potential to be used in integrated microfluidic applications such as bio/chemical analysis and lab-on-a-chip applications.
Micropumps play a crucial role in the microfluidic devices through their exact control and manipulation of fluid at the microscale. Advancements have been made in the creation of micropumps for applications ranging from chemical synthesis to biomedical applications. In this chapter an overview of the most recent developments in micropump technology and design, starting with understanding the working principles of micropumps like electrostatic, pneumatic, etc.as well as differences between Mechanical and Non-Mechanical pumps will be described. This chapter contains the recent developments in microfluidic channels, valves and actuators, as well as some general methods of fabrication of these micropumps (like soft-lithography, MEMS fabrication) along with examples. In the penultimate section, the chapter elaborates on the various applications of micropumps in environmental monitoring (such as particle counting, leak detection, etc.) and biomedical applications and point of care equipment. Finally, the chapter concludes about the future and markets of micropumps.
As a main component, membrane micropumps play a key role in developing microfluidic systems. This part pumps fluids by deflecting a membrane using a micro-actuator with a deflection range of a few micrometers during a few seconds. Most electromagnetic micropumps have low lifetime and fracture toughness or low recovery speed. Micropumps with metallic mass-spring structures can overcome the mentioned disadvantages or limitations. This study investigated the fabrication and characterization of a novel electromagnetic micropump. The proposed micropump consists of a stainless-steel mass-spring structure, a polydimethylsiloxane (PDMS) body and membrane, a permanent NdFeB magnet, a micro-coil, and a 3D printed spacer. To characterize the micropump, the effects of the frequency and duty cycle of the electric current applied to the micro-coil on the micropump flow rate and the membrane deflection vs. time were investigated. A membrane deflection of ±8 µm was obtained in 4 s by applying 1000 mA electrical current to the micro-coil. The maximum volumetric flow rate of 523 nL/s was obtained at a frequency of 125 mHz and a duty cycle of 50%. The von Mises stress distribution in the micropump membrane and variations of the fluid velocity in the microchannels were analyzed using the finite element method (FEM).
In this paper, we first report a micropump actuated by surface tension based on continuous electrowetting (CEW). We have used the surface-tension-induced motion of a mercury drop in a microchannel filled with an electrolyte as actuation energy for the micropump. This allows low voltage operation as well as low-power consumption. The micropump is composed of a stack of three wafers bonded together. The microchannel is formed on a glass wafer using SU-8 and is filled with electrolyte where the mercury drop is inserted. The movement of the mercury pushes or drags the electrolyte, resulting in the deflection of a membrane that is formed on the second silicon wafer. Another silicon wafer, which has passive check valves and holes, is stacked on the membrane wafer, forming inlet and outlet chambers. Finally, these two chambers are connected through a silicone tube forming the complete micropump. The performance of the fabricated micropump has been tested for various operation voltages and frequencies. We have demonstrated actual liquid pumping up to 70 μl/min with a driving voltage of 2.3 V and a power consumption of 170 μW. The maximum pump pressure is about 800 Pa at the applied voltage of 2.3 V with an operation frequency of 25 Hz.
This paper presents the fabrication of a microsyringe, which can be attached to the end of a microintravascular endoscope for drug injection. The syringe consists of a drug chamber and an actuator chamber, which are separated by a silicone rubber membrane. The drug chamber is filled with liquid drug by the membrane actuation caused by the vaporization and condensation of the working liquid in the actuator chamber. The liquid drug, less than 1 μl, is ejected through a nozzle by the bubbles generated from the electrolysis of the working liquid. The syringe is fabricated by micromachining. The deflection of membrane for the each method has been measured. The liquid ejection volume has been measured from the video images captured during the electrolysis of the electrolyte. The average speed at nozzle from 0.1 to 1 s is about 0.14 m/s. Further, the successful operation of the microsyringe under the normal blood pressure was verified.
We survey progress over the past 25 years in the development of microscale devices for pumping fluids. We attempt to provide both a reference for micropump researchers and a resource for those outside the field who wish to identify the best micropump for a particular application. Reciprocating displacement micropumps have been the subject of extensive research in both academia and the private sector and have been produced with a wide range of actuators, valve configurations and materials. Aperiodic displacement micropumps based on mechanisms such as localized phase change have been shown to be suitable for specialized applications. Electroosmotic micropumps exhibit favorable scaling and are promising for a variety of applications requiring high flow rates and pressures. Dynamic micropumps based on electrohydrodynamic and magnetohydrodynamic effects have also been developed. Much progress has been made, but with micropumps suitable for important applications still not available, this remains a fertile area for future research.
The design of a micropump employing only one valve is presented. This device was simulated by means of a model based on electrical analogies and equivalent networks. With a total size of , and a working voltage of 10 V, the device sizing gives flow rates in the 10 - 100 range, which are very suitable for drug-delivery applications.
Piezoelectric bimorph actuation has been successfully used in numerous types of microdevices, most notably micropumps. However, even for the simple case of circular geometry, analytical treatments are severely limited. This study utilized the finite-element method to optimize the deflection of a circular bimorph consisting of a single piezoelectric actuator, bonding material and elastic plate of finite dimensions. Optimum actuator dimensions were determined for given plate dimensions, actuator-to-plate stiffness ratio and bonding layer thickness. Dimensional analysis was used to present the results for fixed-and pinned-edge conditions in a generalized form for use as a design tool. For an optimally-thick actuator, the optimum actuator-to-plate radius ratio ranged from 0.81 to 1.0, and was independent of the Young's modulus ratio. For thin plates, a bonding layer minimally affected the optimum dimensions. The optimized actuator dimensions based on a model of an actual device were within 13% of the fixed-edge condition.
In this paper, a micromachined pump is presented that uses ultrasonic flexural plate waves traveling along a thin membrane to excite an acoustic field in the fluid that is in contact with the membrane. The acoustic field generates fluid flow by the mechanism of acoustic streaming. A novel combination of radial transducers and unidirectional fluid flow produces a fluid micropump capable of achieving flow speeds up to 1.15 millimeters per second, much faster than flow speeds previously obtained. In addition, the radial transducers successfully focused 2-micron polystyrene spheres over a beam waist of less than 100 microns. Also presented are techniques used to characterize thipt>
Many of the compounds in drugs cannot be effectively delivered using current drug delivery techniques (e.g., pills and injections). Transdermal delivery is an attractive alternative, but it is limited by the extremely low permeability of the skin. As the primary barrier to transport is located in the upper tissue, Micro-Electro-Mechanical-System (MEMS) technology provides novel means, such as microneedle array and PZT pump, in order to increase permeability of human skin with efficiency, safety and painless delivery, and to decrease the size of the pump. Microneedle array has many advantages, including minimal trauma at penetration site because of the small size of the needle, free from condition limitations, painless drug delivery, and precise control of penetration depth. These will promote the development of biomedical sciences and technology and make medical devices more humanized. So far, most of the insulin pumps being used are mechanical pumps. We present the first development of this novel technology, which can assemble the PZT pump and the microneedle array together for diabetes mellitus. The microneedle array based on a flexible substrate can be mounted on non-planar surface or even on flexible objects such as a human fingers and arms. The PZT pump can pump the much more precision drug accurately than mechanical pump and the overall size is much smaller than those mechanical pumps. The hollow wall straight microneedle array is fabricated on a flexible silicon substrate by inductively coupled plasma (ICP) and anisotropic wet etching techniques. The fabricated hollow microneedles are 200μm in length and 30μm in diameter. The microneedle array, which is built with on-board fluid pumps, has potential applications in the chemical and biomedical fields for localized chemical analysis, programmable drug-delivery systems, and very small, precise fluids sampling. The microneedle array has been installed in an insulin pump for demonstration and a leak free packaging is introduced.
A bubble-powered micropump which consists of a pair of nozzle-diffuser flow controller and a pumping chamber was fabricated
and tested in this study. The two-parallel micro line heaters were fabricated to be embedded in the silicon dioxide layer
above a silicon wafer which serves as a base plate for the micropump. A pumping chamber, a pair of nozzle-diffuser unit and
microchannels including the liquid inlet and outlet port were fabricated by etching through another silicon wafer. A glass
wafer having two holes of inlet and outlet ports of liquid serve as upper plate of the pump. Sequential photographs of bubble
nucleation, growth and collapse were visualized by CCD camera. The liquid flow through the nozzle during the period of bubble
growth and slight back flow of liquid at the collapse period can be clearly seen. The volume flow rate was found to be dependent
on the duty ratio and the operation frequency. The volume flow rate decreases as the duty ratio increases in the micropump
with either circular or square pumping chamber.
A microfluidic pump is presented using an AC magnetohydrodynamic (MHD) propulsion system in which the Lorentz force is used to propel an electrolytic solution along a microchannel etched in silicon. This micropump has no moving parts, produces a continuous (not pulsatile) flow and is compatible with solutions containing biological specimens. Theory, fabrication method and experimental results are described.
In this paper a bimetallic thermally-actuated membrane micropump is presented. The micropump have been fabricated using silicon micromachining technique. The pump consists of two chips and comprises a pump chamber, two bimetallic actuators and two check valves integrated on the same structure. The size of the pump chamber is about 3mm × 3mm × 0.7mm, and that of microvalve outlet is 100 μ × 100 μm. Flow characteristics of the pump and its main components are tested and discussed. The maximum flow rate of the pump is approximately 43 μl/min, under the driving voltage of 16V and frequency of 0.9 Hz.
Many of the compounds in drugs cannot be effectively delivered using current drug delivery techniques (e.g., pills and injections). Transdermal delivery is an attractive alternative, but it is limited by the extremely low permeability of the skin. Because the primary barrier to transport is located in the upper tissue, Micro-Electro-Mechanical-System (MEMS) technology provides novel means in terms of both micro needle array and PZT pump, with the former one to increase permeability of human skin with efficiency, safety and painless delivery, and the latter one to decrease the size of the pump. Micro needle array has many advantages, including minimal trauma at penetration site due to the small size in needle, no condition limit, painless drug delivery for penetration depth with few nerves, and precise control of penetration depth for micro needle extension length. The micro needle array drug delivery is precise, painless, effective, clean and neatness, without any inconvenience. This will promote the development of biomedical sciences and technology and makes medical devices more humanized. So far most of the insulin pump has been using mechanical pump. We present the first development of this novel technology which can assemble the PZT pump and the micro needles together for diabetes mellitus. The micro needle array based on a flexible substrate can be mounted on non-planar surface or even on flexible objects such as a human fingers and arms. The PZT pump can pump the much more precision drug accurately than mechanical pump and the overall size is much smaller than those mechanical pumps. The hollow wall straight micro needle array is fabricated on a flexible silicon substrate by inductively coupled plasma (ICP) and anisotropic wet etching techniques. The fabricated hollow micro needles are 200μm in length and 30μm in diameter. The micro needle array, which may be built with on-board fluid pumps, have potential applications in the chemical and biomedical fields for localized chemical analysis, programmable drug-delivery systems, and very small, precise fluids sampling. The micro needle array has been installed in an insulin pump for demonstration and a leak free packaging is introduced.
A membrane micropump with integrated actuator based on bimetal effect was first fabricated using advanced silicon micromachining techniques. The processing and materials used were fully compatible to standard IC fabrication technology. The micropump consists of three silicon chips which form two passive check valves and a pump membrane. In contrast to piezoelectrically, thermopneumatically or electrostatically driven micropumps, our membrane micropump is driven by an aluminum-silicon bimetallic diaphragm and can be operated at standard IC voltage level. The outer dimension of the micropump is 6mm × 6mm × 1mm. The silicon diaphragm itself has an area of 4 × 4mm 2 at a thickness of 20μm. The orifice size of the valves is 400 × 400μm 2, while the movable flaps have a size of 1.25 mm × 1mm × 10μm. A pumping yield of 44 μ1/min was measured at pumping frequency of 0.5 Hz and driving voltage of 5.5 V. An output pressure of 1.1 m H 2O has been achieved. Optimization is undertaken now and the performance is expected to be improved dramatically.
No highly integrated sphincter prosthesis for therapy of major fecal incontinence exists. Therefore, we developed a novel neosphincter, made of polyurethane. The GASS consists of a support ring (SR) which includes a fluid reservoir, fixed on the outer diameter of the SR, and a multi-chamber occluding cuff (Cint) on the inside diameter. The total inflation volume of Cint is about 23 cc. The integrated micropump based on piezotechnology measures 30×13×1 mm3 (flowrate 1.4 cc/min, max. backpressure 40000 Pa). GASS was evaluated around the external sphincter of isolated porcine anal canals. The threshold of continence was defined as the inflating volume wich water ceased to leak through the area occluded by Cint under an induced rectal pressure of 150 cm H 2O. Minimal filling volumes maintained continence for liquids against high luminal pressures. A low intraanal resting pressure (Δp anal) induced by activated GASS indicates a little risk of ischemic injury of the anal canal in vivo (median Δpanal 24.1 mm hg:15cc vs 46.9 mm hg: 21cc). In summary, a highly integrated and efficient high-tech neosphincter for the therapy of major fecal incontinence could be realized.
Implantable electronic devices such as pacemakers and neural implants are often used for electrical stimulation. The usage of microfabrication techniques to produce microelectromechanical systems (MEMS) has allowed engineers to address a wider range of clinical indications. A new direction in the area of MEMS technology is the goal of achieving pulsatile drug delivery. The digital capabilities of MEMS may allow greater temporal control over drug release compared to traditional polymer-based systems, while the batch-processing techniques used in the microelectronics industry can lead to greater device uniformity and reproducibility than is currently available to the pharmaceutical industry. A repertoire of structures, including microreservoirs, micropumps, valves, and sensors, is being developed that will provide a strong foundation for the design of integrated, responsive MEMS for drug delivery.
A normally closed microvalve and a micropump are fabricated on a silicon wafer by micro-machining techniques. The normally closed microvalve has a movable silicon diaphragm and a small piezoactuator to drive it. The controllable gas flow rate is from 0.1 ml/min to 85 ml/min at a gas pressure of 0.75 kgf/cm2. The micropump is a diaphragm-type pump, which consists of two polysilicon one-way valves and a diaphragm driven by a small piezoactuator. The maximum pumping flow rate and pressure are 20 μ/min and 780 mmH2O respectively.
This paper reports on a research effort to design, microfabricate and test an AC-type magnetohydrodynamic (MHD) micropump using UV-LIGA microfabrication. The micropump is driven using the Lorentz force and can be used to deliver electrically conductive fluids. In the AC-type MHD micropump developed in our laboratory, a diffuser/nozzle is integrated with a MHD driving chamber. With a magnetic field supplied by an external permanent magnet, and an AC electrical current supplied across two copper side-walls, the distributed body force generated will produce a pressure difference on the fluid in the pumping chamber. The directional dependence of the flow resistance of the diffuser/nozzle allows for a net output flow in response to the oscillating pressure generated by the sinusoidal current. The major advantage of a MHD-based micropump is that it does not contain any moving parts. It may have potential applications in medicine delivery, and biological or biomedical studies. An AC-driven micropump may be used to improve on the performance obtained in tests of a DC-driven prototype micropump, that showed pumping performance was significantly degraded by bubble generation.
Microelectromechanical systems (MEMS) technology has matured to the point where practical biological and chemical applications are possible. One particularly active research area is in the development of lab-on-a-chip type systems. In order to create successful lab-on-a-chip and other microfluidic systems, it is necessary to have the capability of controlling and directing fluid flow. Such functionality can be found on the front end of a microfluidic system and is known as a fluid delivery or dosing subsystem. For a MEMS micro fluid dosing system to be realized, several components are necessary. The essential components include a fluid actuator, a fluidic control device, and micro plumbing. A prototype fluid delivery system is demonstrated here using a micropump as the fluid actuator, a thermal flow sensor as the fluidic control device, and micromachined couplers as plumbing. The technology to build these components has been developed and each of these components have been fabricated and tested. A prototype constructed of discrete components has also been demonstrated. A truly integrated, channel-based fluid dosing system can be achieved through device scaling.
A novel single-chip integrated microfluidic system is presented. After 3D structures are formed with deep cavities and stiff mechanical membrane as sealing layer in single-chip, additional standard IC processes are applied to achieve single-chip integrated microfluidic systems, including micropumps, valves, channels, cavities and some different sensors. We have applied different principles, bimetallic and electrostatic driving, to the driving and control of the micropumps and microvalves. The final micropump driving membrane is 1 mm×1 mm×2 μm and the valve membrane is 6 mm×0.6 mm×2 μm. Preliminary experiments show that the on/off flow ratio of the integrated micropump is 180. The results of the sensitivity and the temperature coefficient of the sensors are also reported
A silicon micropump, provided with piezoelectric valves, which can be manufactured by established integrated circuit techniques is the subject of this report. The micropump can be used to pump liquids or gases to a higher pressure, which can be relieved through a check valve. The body of the pump and the valves are made in silicon and contain piezoelectric material which allows opening and closing of the valves electrically.
The paper reports data obtained on a simple micropump, suitable for electrolytes, based on the periodic growth and collapse of a single vapor bubble in a microchannel. With a channel diameter of the order of 100 µm, pumping rates of several tens of µl/min and pressure differences of several kPa are readily achieved by the system. The pump is notable for its effectiveness, simplicity, absence of mechanical moving parts, robustness and low cost. In the absence of a complete theory for the device, the data are interpreted and rationalized on the basis of simple physical arguments. It is also shown how the pump can induce strong mixing in two channels coming together at a Y-junction.
This paper describes a novel pumping device without mechanical moving parts based on the periodic generation and collapse of a single vapour bubble in a channel. The channel shape is such that it creates an asymmetry in the surface tension forces, which results in a pumping effect. The principle can be implemented over a broad range of channel sizes and repetition frequencies. For illustration purposes, a particular implementation is described here where the working fluid is a salt solution in water, the channel diameters are of the order of 1 mm and the repetition frequency is between 1-10 Hz. In these conditions, the device develops a head of a few centimetres of water with typical flow rates in the range of 100 µl per minute. It appears possible to increase both head and flow rate by adjusting geometrical parameters and operating conditions. A simple modification of the design would render the same principle also applicable to the pumping of non-conducting liquids.
A process for the fabrication of microvalve systems by thermoplastic molding and membrane techniques has been developed. The valve system consists of three individual valves formed by two parts molded from polymethylmethacrylate PMMA and a polyimide membrane. The mold inserts were manufactured by milling of a brass substrate using a 300 mu m diameter head. The three-dimensional microstructure of the inserts consists of four different levels for valve seats, orifices, alignment pins and cavities. The overall diameter and height of the whole valve system is 7 mm and 1.9 mm, respectively. The valves are designed to be normally open. To close the valves, the pressure in an actuator chamber above the membrane is raised by a heater coil and the membrane is pressed onto the valve seat. First measurements at a difference pressure of 1000 hPa showed a rate of water flow through a single valve of 171 mu l s-1. An actuator pressure of 180 hPa was reached by heating air with a resistive heater and continuous electrical power of 158 mW. A valve supplied with nitrogen at 130 hPa was closed by an electrical power of 116 mW.
The transport of small amounts of fluids and gases must be controlled with a view to automated drug dosage, chemical analysis with microsensors, and hydraulic as well as pneumatic microactuators. Components for microfluidic systems have been developed at Karlsruhe Nuclear Research Center which are manufactured by the LIGA technique. Micropumps have been fabricated by combining thermoplastic molding with membrane techniques. It is envisaged to integrate these micropumps into a module for handling gases and liquids. The module can then be coupled with different sensor modules to form microsystems, e.g. for the detection of toxic chemicals in the environment or for bedside analysis in hospitals. Microvalve systems and fluidic beam amplifiers have been developed for hydraulic and pneumatic actuators. These devices are capable of controlling a liquid or gas stream and may be used to steer e.g. instruments in a catheter tip for minimally invasive surgery.
In this paper a closed-loop controlled micromachined dosing system is presented, for the accurate manipulation of liquids in microsystems down to the nanoliter range. The applied driving force to dispense liquids originates from the electrochemical generation of gas bubbles by the electrolysis of water. The proposed dosing system comprises a micromachined channel/reservoir structure in silicon, capped with a Pyrex® cover on which a set of platinum electrodes is patterned. By adopting an interdigitated electrode geometry, the electrodes can be used for electrochemical gas generation as well as for the simultaneous determination of the total gas bubble volume, via an impedance measurement of the gas/liquid mixture in the reservoir. As this measured gas bubble volume equals the dosed liquid volume, active control of dosed volumes can be obtained. It will be shown that the cell impedance can be applied to accurately determine the generated gas volume and that by using this parameter in a closed-loop control system, dosed volumes can be controlled in the nanoliter range.
In this paper a piezoelectrically driven silicon membrane pump with passive dynamic valves is described. It is designed to pump gases and liquids and to be tolerant to gas bubbles. Reducing the dead volume within the pump, and thus increasing the compression ratio, one achieves the gas pumping. The main advantages and novel features of the pump described in the paper are the self-aligning of the membrane unit to the valve unit and the possibility of using screen-printed PZT as actuator, which enables mass production and thus low-cost micropumps. A liquid pump rate of 1500 μl min−1 and a gas pump rate of 690 μl min−1 were achieved.
A new microvalve actuator driven by electrostatic force is described and shown to be suitable for controlling the flow of a rarefied gas. The actuator consists of a pair of planar electrodes sandwiching a conductive film that has an S-shaped bend in the middle. The S-bend moves back and forth as voltage is alternately applied between each of the electrodes and the film. A manually assembled macromodel actuator having a film 5 mu m thick and 12 mm wide is operated between electrodes separated by 2.5 mm. The propagation speed is 4.0 m s-1 at an applied voltage of 150 V. The large vertical displacement of the film enables the large valve seat lift necessary to allow a certain amount of gas flow. An experimental model of the valve allowed at airflow rate of 10 sccm at a pressure of 60 Pa.
A novel electrostatically actuated valveless micropump is presented whereby an actuation voltage is applied across a working fluid, which takes advantage of the higher relative electrical permittivity of water and many other fluids with respect to air. The device is fabricated in silicon and the diaphragm is made of electroplated nickel, while the assembly is carried out using flip–chip bonding. A reduced-order model is used to describe the micropump's performance in terms of electrical properties of the fluid, the residual stress in the diaphragm, geometrical features and the actuation voltage. The tested prototype featured a ~1 µl min−1 flow rate at 50 V actuation voltage. The model predictions show the possibility of achieving flow rates >1 µl min−1 with the actuation voltage <10 V for devices with 3 mm diaphragm size.
An electrochemical syringe pump was fabricated by micromachining. Two sets of thin-film three-electrode systems for actuation and sensing were formed on a glass substrate, whereas a microflow channel and a microcontainer for the internal electrolyte solution were formed on a silicon substrate. Hydrogen gas produced or consumed on a platinum black working electrode was used as a working medium. The rates of pumping for flushing and sampling could be varied by adjusting the potential of the working electrode at appropriate values to reduce and oxidize the related species. As a result, bi-directional pumping could easily be realized. During pumping repeated up to 20 times, the deviation of the pumping rates was distributed within 7% of the respective averages. The function of the micropump incorporated in a system was tested using a solution containing Cu 2þ ions and a distinct current increase accompanying the reduction of the ions was observed following the sampling. When the goal is to reduce power consumption, the material used for the auxiliary electrode is critical and Ag/AgCl was considered to be a good alternative for a platinum auxiliary electrode. # 2002 Elsevier Science B.V. All rights reserved.
In this paper, a phase-change type micropump is presented. This micropump consists of a pair of aluminum flap valves and a phase-change type actuator. The actuator is composed of a heater, a silicone rubber diaphragm and a working fluid chamber. The diaphragm is actuated by the vaporization and the condensation of the working fluid. The micropump is fabricated by the anisotropic etching, the boron diffusion and the metal evaporation. The dimension of the micropump is 8.5 mm × 5 mm × 1.7 mm. The forward and the backward flow characteristics of the flap valve illustrate the appropriateness as a check valve. The flow rate of the micropump is measured for various voltages, frequencies and duty cycles of the square-wave input. When the square-wave input voltage of 10 V is applied to the heater, the maximum flow rate of the micropump is 6.1 µl min −1 at 0.5 Hz and the duty ratio of 60% for zero pressure difference. The maximum backward pressure when the flow rate is zero is 10 mm H 2 O.
Since most of miniaturized surface plasmon resonance (SPR) sensing systems need commercially available peristaltic or syringe
pumps, it is difficult to reduce the system size, biosample volume, and the production cost. In this paper, a compact biochip
for clinical diagnosis is presented. The proposed biochip is integrated traveling wave micropumps and SPR imaging sensors
on one chip. The micropump is composed of flexible microchannel and piezoelectric bimorph actuator array, and achieved the
maximum flow rate 336μl/min. The SPR imaging biosensor can quantitatively measure biosamples with multi microchannels, i.e.
one biosample and two reference flows to obtain an analytical curve. The SPR imaging measurements with bovine serum albumin
solutions were carried out using the prototype of the proposed diagnostic system composed of a pair of the micropump and the
sensor. Since the clear SPR signal curve was observed, it was confirmed that the proposed system can be applicable to the
clinical diagnosis.
An inexpensive and simple pumping principle is described that is capable of delivering both small and constant flow rates (10–1,000 nl/min) over a longer period of time (days to weeks). The concept is based on controlled evaporation of a liquid through a membrane into a gas space containing a sorption agent. As long as the sorption agent keeps the vapor pressure in the gas phase below saturation, fluid evaporated from the membrane is replaced by capillary forces inducing flow from a reservoir. In a feasibility study, a total volume of 300 µl of Ringer's solution has been continuously pumped over a period of six days, resulting in an constant average flow rate of 35 nl/min (590 pl/s). The maximum liquid volume transported is limited by sorption capacity and amount of the sorption agent. Low fabrication costs, high reliability (no moving parts), the suitability for integration into planar system architectures and the lack of a special external energy source besides an environment of regulated temperature are important features of the concept, in particular with regard to its potential application in continuous patient monitoring. Truly continuous flow can be achieved in contrast to many other pump mechanisms leading to discontinuous, pulse-type flow. A challenge for a broader range of applications is the inherent temperature dependence of the flow rate. In its current version, the pump can only be used in a suction-mode.
This study involves the design, fabrication and characterization of a biocompatible silicon micropump. Three experiments were
conducted to study the performance of this pump in clinical environments. They were a blood compatibility test, and in vitro
and ex vivo studies. Whole blood is an intrinsically complex material and difficult to manipulate using a microsystem device.
In the blood compatibility experiments, two materials N-(triethosilylpropyl)-O-polyethylene oxide urethane (PEOU) and polyethylene glycol (PEG) were employed to form a self-assembled monolayer (SAM) on
a chip surface. According to the platelet remaining test and a 30-min blood transportation test, PEOU protected the micropump
from thrombus. In the second experiment, the micropump handled several liquids, including DI water and whole blood. When the
pump was operated at a voltage of 140Vpp, the flow rates of the DI water and whole blood were 121.6μl/min at 500Hz and 50.2μl/min at 450Hz, respectively. The
maximum back pressure of the water and the blood in the micropump were 3.2 and 1.8kPa, respectively. Finally, the micropump
injected phosphated buffered saline (PBS) and whole blood into the veins of rats. The pump was characterized ex vivo and discussed.
The third experiment reveals that the micropump fulfilled the dosing condition for clinical medicine and did not affect the
physiological function of the rats. This pump is highly promising for biomedical applications, such as in drug delivery for
patients, or in clinical care. Moreover, the pump has potentials to control precisely medication to improve conventional clinical
treatments.
This paper reports a research effort to design, microfabricate and test a DC type magnetohydrodynamic (MHD) micropump using
LIGA method (Menz et al., 1991). The micropump is driven using the Lorentz force and can be used to deliver electrically conductive fluids. In operation, a DC voltage is supplied across the electrodes
to generate the distributed body force on the fluid in the pumping chamber, and therefore a constant pressure difference along
the pumping chamber. The external magnetic field was supplied using permanent magnets. The major advantage of a MHD-based
micropump is that it does not contain any moving parts. It may have potential applications in medicine delivery, biological
and biomedical studies. The test of the DC prototype micropump shows that bubble generation mechanism affect the performance
significantly and an AC driving mechanism may be used to improve the performance.
We present - for the first time - a novel design of a micropump which enables a backpressure-independent flow rate up to 20 kPa within the low flow regime required for drug delivery systems. Our concept, based on two piezoelectrically actuated diaphragms, allows an accurate dosing in the range of 1 - 50 µ l/min with freely programmable release profiles and offers the potential to minimize chip size and power consumption in comparison to 3-actuator peristaltic micropumps. The stroke volume is adjustable between 50 - 200 nl by means of voltage control which enables a high resolution volumetric dosing. Within the relevant frequency range below 2 Hz the flow rate is proportional to the frequency. Our design also excels in its comparably simple and robust 2-layer fabrication process.
We have observed pumping of water induced by 4.7 MHz ultrasonic Lamb waves traveling in a 4‐μm‐thick composite membrane of silicon nitride and piezoelectric zinc oxide. The observed pumping speed is proportional to the square of the wave amplitude; the speed was 100 μm/s for a rf drive voltage of 8 V and a 6.5 nm wave amplitude. A nonlinear model based on acoustic streaming theory predicts velocities in good agreement with experiment.
A novel electrostatic micromachined pump for medical applications is designed and simulated. The proposed structure for the micropump consists of an input and an output port, three membranes, three active membrane valves, microchannels, and three electrostatic actuation systems. Pumping mechanism of the proposed micropump is based on the peristaltic motion that has some advantages, such as high controllability and precision, over the other mechanism that makes it suitable to be used for the medical applications. Electrostatic actuation has been employed for the deflection of the membranes because of its benefits, such as the smaller size of the device in comparison with the other types, especially piezoelectric counterpart and so on. Employing active membrane valves instead of passive check valves resolves some of the problems, such as valve clogging and leakage. The designed micropump satisfies all medical drug delivery requirements, such as drug compatibility, flow rate controllability, self-priming, small chip size, and low power consumption. The flow rate of the designed micropump is 9.1 μl/min which is quite suitable for drug delivery applications, such as chemotherapy. Total size of the designed micropump is 7 mm × 4 mm × 1 mm, which is smaller than the other peristaltic counterpart micropumps. Assuming zero residual stress, low actuation voltage, and small size are the main advantages of our design. The designed micropump is simulated by the finite element method, using the ANSYS 5.7 software.
A plastic micropump which can be produced using conventional production techniques and materials is presented. By applying well-known techniques and materials, economic fabrication of micropumps for various applications is feasible even at low production volumes. The micropump is capable of pumping both liquid and gas at a considerable high pump rate and is self-priming, which means that it can start pumping gas in a dry state and automatically fills with liquid. Pump rates, at actuation frequencies between 2 and 500 Hz, were around 2 ml/min for water and up to 50 ml/min for air. A differential pressure of 1.25×104 Pa (125 cm water column) was reached. Basically, the micropump consists of two parts, a flat valve assembly with two passive membrane valves and an actuator placed on top. The valves were made by sandwiching a punched thin polymer film between two plastic valve parts containing the valve seats. The latter parts are made by reactive injection molding of an epoxy resin. Two types of actuators have been applied to drive the pump; an electromagnetic actuator consisting of a magnet placed in a coil and secondly a disk. The first actuator, when combined with a flexible polymer pump membrane, showed a very large pump rate for gas, up to 40 ml/min at the resonant frequency of the actuator system. A disadvantage of the electromagnetic actuator was the relatively large volume occupied by the coil giving the micropump final dimensions of 10×10×8 mm3. Application of the piezoelectric actuator reduced these dimensions down to 12×12×2 mm3 with comparable performance.
With a micropump, the release rate of drug delivery is able to be controlled easily to maintain the therapeutic efficacy. A high-performance piezoelectric cantilever-valve micropump was investigated for this purpose. The effect of valves on the output performance of the PZT micropump was analyzed at first. With taking into account the influence of liquid added mass and added damping on the natural frequency of the valves and actuator, the design method of the cantilever valve was presented. Two micropumps were designed and fabricated for comparing experiments. The micropump with cantilever valves 2.5 mm in length obtained higher output values (the maximum flow rate and backpressure is 3.5 ml/min and 27 kPa, respectively) and had two optimal frequencies (0.8 and 3 kHz). While the micropump with cantilever valves 4.5 mm in length had only one optimal frequency (0.2 kHz), at which the micropump achieved lower output values (the maximum flow rate and backpressure is 3.0 ml/min and 9 kPa, respectively). The study results suggest that the output values and optimal frequency of micropump can be improved by the design of the cantilever valves.
The objective of the study described here was to explore the possibility of constructing a multi-stage electroosmotic pump (EOP). The 1–3-stages EOP have been fabricated using μm i.d. 2 μm porous silica particles packed-columns, fused-silica capillaries and stainless electrodes and their performances were characterized. When the power supply was connected to the electrodes of the pumps in parallel, compared with the 1-stage EOP, the out pressures of the 2- and 3-stage EOP were about 2- and 3-fold increase, respectively, and the flowrates of the 2- and 3-stage EOP were identical with that of the 1-stage EOP, at the same driving voltage. The multi-stage EOP, i.e., the n-stage EOP could be constructed using n packed-columns, n−1 narrow bore capillaries and n pairs of electrodes connected in series. When the counter flow in the capillaries FCON was regulated to be negligible, the output pressure PEOP (n) of n-stage EOP was n× PEOP(1) of 1-stage EOP with the flow rate unchanged at the same driving voltage, which demonstrated a potential application on a chip as a microfluidic component.
We present the design, fabrication and testing of a novel medical implant based on a high performance silicon micropump. An analytical model was exploited for further optimization of our micropump design. The experimental data obtained are in a good accordance to theory. The limits of the analytical model are discussed and numerical studies are performed to examine the pressure loss over the valves of the micropump in detail. The presented micropump shows a flow rate of 1.8 ml/min and can build up and maintain backpressures up to 60 kPa. The overall size of the micropump is 30 mm × 11 mm × 1 mm. The driver electronics for the piezoelectric actuators is explained and the energy consumption is estimated. Two sphincter prosthesises of different sizes were developed and tested. The general medical capability as a prosthesis has been proven.
This paper presents fabrication and drive test of a peristaltic PDMS micropump actuated by the thermopneumatic force. The micropump consists of the three peristaltic-type actuator chambers with microheaters on the glass substrate and a microchannel connecting the chambers and the inlet/outlet port. The micropump is fabricated by the spin-coating process, the two-step curing process, the molding process using negative photoresist, etc. The diameter and the thickness of the actuator diaphragm are 2.5 mm and 30 μm, respectively. The meniscus motion in the capillary tube is observed with a video camera and the flow rate of the micropump is calculated through the frame analysis of the recorded video data. The maximum flow rate of the micropump is about 0.36 μL/s at 2 Hz for the zero hydraulic pressure difference, when the three-phase input voltage is 20 V.
A circular ac magnetohydrodynamic (MHD) micropump for chromatographic purposes has been developed. The device consists of a glass–gold-laminate–glass sandwich structure, with the channel structure defined in the electroformed gold layer. Channels were 200 μm wide and 30 μm high. Experimental details on the manufacturing of the device and the optimisation of the setup are presented. Reversible flow of maximally 40 μm s−1 has been obtained. The flow speed attained and the small channel height make the device in principle suitable to perform circular chromatography.
Electroosmotic flow (EOF) micropumps which use electroosmosis to transport liquids have been fabricated and used to achieve pressures in excess of 20 atm and flow rates of 3.6 μl/min for 2 kV applied potentials. These pumps use deionized water as working fluids in order to reduce the ion current of the pump during operation and increase thermodynamic efficiency. EOF pumps are fabricated by packing the 3.5 μm diameter non-porous silica particles into 500–700 μm diameter fused-silica capillaries and by using a silicate frit fabrication process to hold the particles in place. The devices have no moving parts and can operate as both open (high flow rate) and closed (high pressure) systems. Pressure versus flow rate performance data are presented and combined with measurements of physical dimensions, dry and wet weight, and ion current to calculate the pump structure porosity, tortuosity, effective pore radius, and zeta potential.
If a high and on-going research dynamics is taken as a rejuvenating factor microfluidics can still be regarded as a truly young discipline, although some microfluidic devices definitely can not be considered as “youngsters” any more. In a time of 30 years of ISFETOLOGY it may be worth to take a look at these devices in order to examine, whether they had—and still have—the potential to stimulate the imagination and creativity of researchers in a similar way as the Ion Sensitive Fieldeffect Transistor did since its invention in 1970. The area of micropumps is definitely one of those “long runners”. Starting in the mid 1970s a steadily growing and astonishing diversity of micropump principles, technical concepts and applications has emerged in this area. Until today MEMS science is delivering a constant flow of novel modelling approaches, microstructured materials, actuation principles, fabrication technologies and applications, that are readily taken and transferred into micropump research. Among the potential applications especially the combination of biochemical sensing and microfluidics has provided a substantial stimulus for micropump research and development in the past and will do so in the future.
A thermopneumatic-actuated polydimethylsiloxane (PDMS)-based micropump has been fabricated and its properties have been characterized. Diffusers are used as flow-rectifying elements instead of passive check valves. The advantages of the proposed micropump are the low cost fabrication process and the transparent properties of the PDMS and indium tin oxide (ITO)-coated glass. We present a PDMS micropump that is easily integrated with in-channel PDMS microvalves on the same substrate. The flow rate of the micropump increases linearly with increasing applied pulse voltage to the ITO heater with resistance of 6.54 kΩ. The peak flow rate of 78 nl/min is observed at the duty ratio of 10% for the applied pulse voltage of 55 V at 6 Hz.
This paper presents a novel micropump of which pumping mechanism is based upon magnetohydrodynamic (MHD) principles. MHD is the study of flow of electrically conducting liquids in electric and magnetic fields. Lorentz force is the pumping source of conductive, aqueous solutions in the MHD micropump. Conducting fluid in the microchannel of the MHD micropump is driven by Lorentz force in the direction perpendicular to both magnetic and electric fields. The performance of the micropump is obtained by measuring the pressure head difference and flow rate as the applied voltage changes from 10 to 60 VDC at 0.19 and 0.44 Tesla (T). The pressure head difference is 18 mm at 38 mA and the flow rate is 63 μl/min at 1.8 mA when the inside diameter of inlet/outlet tube is 2 mm and the magnetic flux density is 0.44 T. Bubble generation by the electrolysis of the conducting liquid can be observed. The performance of the MHD micropump obtained theoretically in single phase is compared with the experimental results.