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We developed a maskless lithography system using a digital micromirror device (DMD). This system incorporates a light-emitting diode (LED) driver to generate ultraviolet (UV) light, illumination optics using a fly-eye lens, and telecentric projection optics to generate a parallel light source reflected from the DMD. The potential problems caused by...
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Over the past few decades, polydimethylsiloxane (PDMS) has become the material of choice for a variety of microsystem applications, including microfluidics, imprint lithography, and soft microrobotics. For most of these applications, PDMS is processed by replication molding; however, new applications would greatly benefit from the ability to patter...
We present a reproducible process to directly pattern 3-Dimensional (3D) polydimethylsiloxane (PDMS) structures for Organ-on-Chips (OOC) via automated molding. The presented process employs a commercially available system from IC packaging improving the fabrication process for microfluidic channels and thin membranes, which are components frequentl...
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... This unidirectional flow can be further utilized in the following stages [1,2]. Microfluidic chips can be used in bio/medical applications [3,4], e.g., cell separation [5], obtaining particles for drug delivery [5][6][7][8][9], mixing [10][11][12][13], and micro-pumping [14,15], or in industrial scales, e.g., turbines [16], or heat pumping [17,18], heat removal [19], wastewater treatment [20][21][22][23][24], bacteria removal [25], and chemical reactions under hydrodynamic cavitation conditions [26][27][28][29][30], or in larger-scale applications, e.g., a passive safety system in a molten salt reactor [31], energy harvesting [32][33][34][35], or ventilation purposes [36]. Fluidic diodes can be separated into two groups: passive and active. ...
The performed research presents modeling results for designing microfluidic vortex diodes. These devices rectify fluid flow and can be used in many applications on micro and macro scales. The modeling, utilizing computational fluid dynamics (CFD) with the turbulence model RANS k-ε in COMSOL Multiphysics, has led to optimizing diodicity—the reversed-to-forward flow pressure drop ratio. The goal was to find the best flow-rectifying geometry within the 2D vortex-type design by changing the wall geometry, diode shape, and inflow velocities, identifying significant parameters and dependencies. Improving diodicity can be achieved by increasing the radius r1 of the central channel, increasing the entire diode radius r2, decreasing the width w of the rectangular channel, and reducing its length L. Additionally, changing the circular shape of the diode to an elliptical one can improve diodicity. The significance of this research is evident in the potential applications of these devices in microfluidic setups where fixed-geometry unidirectional flow is required, e.g., mixing, filtration, cell separation, and drug delivery, or on industrial scales, e.g., energy harvesting, wastewater treatment, and water sterilization.
... Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. board manufacturing [5][6][7], microfluidic devices [8,9] and bioapplications [10,11]. In digital lithography system, a DMD dynamically generates various UV patterns, controlling each micromirror to rotate to the 'ON' or the 'OFF' state. ...
The rough saw-tooth edge caused by the inherent microstructures of digital micromirror device (DMD) will reduce the quality of the lithography pattern. Comprehensively considering the manufacturing efficiency, precision and cost, we propose a DMDs collaborative modulation lithography method to improve the smoothness of the lithography pattern edge. Through combining two misaligned DMDs to collaboratively modulate exposure dose, the better edge smoothness can be achieved. Collaborative exposure with 1/2 DMD pixel misalignment and 1/4 DMD pixel misalignment are both implemented to form the step-shape lithography patterns. The experimental results show that the saw-tooth edge can approximate to a straight line when increasing the number of times of the collaborative exposure. Further error analysis indicates it is effective to improve the edge smoothness while ensuring the lithography quality by using the collaborative modulation lithography. These results indicate that the DMDs collaborative modulation lithography is a promising technique for fabrication of microstructures, which may be a solution for balancing the fabrication precision, efficiency and cost.
... Soft lithography technique has many advantages such as relatively fast and cheap prototyping, batch manufacturing and possibility of achieving high aspect ratio microstructure. Reports have been made on soft lithography technique for the fabrication of various microfluidic devices such as micromixers, microreactors and micropump for biosensors and cell sorting applications [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. The fabrication issues in flexible polymer microfluidic device using hot embossing process was discussed [24]. ...
In this paper, we discuss about critical issues in fabrication of polymer microfluidic devices which affect the dimensions of the microchannel and hence the volumetric analysis of the fluids. The optical and thermal properties of the materials used in the fabrication of devices determine the final structural dimensions and the reliability of the fabricated devices. A clear understanding of material properties and their effect on the dimensional variations of microfluidic devices during fabrication are essential in different applications such as micro dispensers, micro pump, micro mixers and micro reactors. It is possible to obtain microfluidic devices with perfect dimensions by carrying out the fabrication processes with perfect timing control and precisely controlled temperature during fabrication. This paper focuses on the dimensional stability of SU8 prime mould with respect to UV exposure time, effect of temperature on PDMS replicas and the effective sealing of the device by adhesive bonding.
Local anesthesia is widely used in the treatment of postoperative pain. Long time duration and constant release of the local anesthetic is important for pain control. In this study, a preparation method of porous Poly (lactic-co-glycolic acid) (PLGA) microparticles loaded with local anesthetic, lidocaine was studied. Microfluidic flow-focusing device was used to prepare monodispersed microparticles. A phosphate buffer solution (PBS) was used as porogen. The geometry of microparticles was analyzed, and the drug release profile was determined by UV spectroscopy. Test results showed that porous microparticles are beneficial for sustained release of local anesthetic in long time duration over 40 days.
Micromixers are the microfluidic devices able to rapidly mix more than two liquids, with low pressure drop and high mixing efficiency (εmixing). In this study, the effect of Reynolds number ratio (Rer) and aspect ratio (AR) of heart-like biometric micromixer applied would be investigated by a numerical simulation and experimental confirmation. Results show that the heart-like biometric micromixer resulting from the coupling effect of the split and recombination (SAR) and biometric design can produce a high mixing efficiency, low pressure drop and short mixing path under a case of low Reynolds number. Two dimensional results also find that a flow mixing efficiency of εmixing=0.89 and an optimal mixing index of Midx=115 could be achieved at a flow condition of Rer=0.75 and Re2=0.1 of the middle-inlet channel I2. In additional, the three dimensional results indicate that a high flow mixing efficiency of εmixing=0.84 and the lowest pressure drop of 164.2 Pa was obtained at the flow conditions of Rer=0.9 and AR=10 when the middle-inlet channel I2 was Re2=0.1. These findings will be useful to improvement the efficiency for micromixcers of biometric design in the future.
Digital-mask lithography systems, with a digital micromirror device (DMD) as their central piece, have been widely used for defining patterns on printed circuit board (PCB). This study designed optical module parameters for point-array projection lithography based on field tracing technique to improve the quality of the aerial image on the exposure plane. In the realized optical module for the point-array projection lithography, a DMD was used as the dynamic digital-mask, and a 405-nm-wavelength laser was used to illuminate the DMD. The laser was then focused through the micro-lens array in the optical module to form a point array and was projected onto a dynamic scanning stage. By calculating the beam-overlapping rate, stage velocity, spot diameter, and DMD frame rate and programming them into the stage- and DMD-synchronized controller, the point array formed line patterns on the photoresist. Furthermore, using pulse width modulation (PWM) technique to operate the activation periods of the DMD mirrors effectively controlled the exposure and achieved a feature linewidth of less than 10 μm.