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This work has focused on the design simulation analysis of a Polysilicon-based CMOS micromachined Piezoresistive Microcantilever beam for glucose sensing application. In principle, adsorption of glucose on a functionalized surface of the microfabricated cantilever will cause a surface stress and consequently the cantilever bending. In this paper, the microcantilever beam is constructed and bending analysis is performed so that the beam tip deflection could be predicted. The device model was simulated using CoventorWareTM, a commercial finite element analysis (FEA) tool designed specifically for MEMS applications. The structural variationof the piezoresistors designs on cantilever beam is also considered to increase the sensitivity of the microcantilevers sensor since the forces involved is very small. Besides, the mechanic characteristics of the microcantilever beam such as displacement were observed based on transient response characteristics using analytical method and simulation method with Matlab Simulink. We observed that the best output response which have fastest response, low overshoot and low steady state error is when d=3.30 and k=3.

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... In "in-vivo biosensing", where small cells are usually experimented for analysing the whole organism, microcantilever are generally preferred for sensing. The lower level detection ability and simple structure make these cantilevers more applicable in many applications like TG detection [16], continuous glucose monitoring [15], lab on chip [7], RF frequency alteration [13] and many other. 2 Microcantilevers are the structure which is mainly hinged at one end and free at other end, hence can easily deform (or deflected) by the applied uniform analyte pressure. ...

... 2 Microcantilevers are the structure which is mainly hinged at one end and free at other end, hence can easily deform (or deflected) by the applied uniform analyte pressure. However, rectangular cantilever beam are used for TG and glucose detection [2,15,7], as a RF switch for switching [1,12,13], antigen-antibody reaction [3] and many chemical and biological species concentration measurement. But their constant geometry makes them less effective in lower mass detection. ...

... The slotted or fractal surface gives good analyte adhesion and improves the sensor sensitivity. Henceforth, these designs can be used in lower mass loading application like TG detection [2,16] or glucose detection [15] at much lower concentration of blood serum nearly 1 or 2pl or less. The FEM software Intellisuite is used for modelling, virtual fabrication and analysis. ...

Surface geometry plays an important role in case of analyte sensing and RF switching using beams and electrodes. In general, rather than simply supported beam and diaphragm, microcantilever beams are widely preferred in BIO-MEMS and RF-MEMS for biosensing and RF switching, respectively. The lower level detection ability and simple structure make these cantilevers more applicable in many applications. The rectangular cantilever beams are most widely used in TG detection. but due to their constant or planner geometry and non-adhesion of analyte they are less sensitive in case of nano or pico level biosensing. This paper introduces the fractal surface geometry concept for increasing the deflection sensitivity corresponding to lower molecular or analyte loading. The rectangular and stepped cantilever beam structures along with fractal surface are simulated and analysed for TG molecular pressure 294.3 Pa. Both the rectangular and stepped microcantilever beams with fractal surface exhibit better free end or tip deflection (nearly 2×) as compare to the planner surface based beam. The proposed fractal concept also reduces the actuation voltage requirement for perfect switching.

... In bio- MEMS, molecular mass and concentration can be inspected by microcantilever based biosensor [3, 4]. MEMS sensors are also utilized for TG [5] and glucose [6] detection. Potentiometric and amperometric type biosensors are also used for sensing purposes [1] . ...

High performance and sensitivity of a microcantilever beam is much demanded in biosensing and needs accurate measurement of tip deflection under very low range of analyte adhesion. Constant geometry based rectangular microcantilevers are not good enough for micro or pico level triglyceride (TG) and glucose detection. With the same surface area, length and thickness, the proposed variable width based stepped microcantilever beams exhibit nearly twice or thrice more tip deflection corresponding to the same TG and glucose molecular pressure. With the less pull-in voltage requirement, such proposed stepped microcantilever beam based switches can be utilized in RF reconfigurable antenna for altering its operating frequency and radiation properties. Several configurations of proposed microcantilevers have been studied and analyzed for finding the optimal design with better deflection sensitivity. This paper also encompasses the mathematical modeling of proposed single and double stepped microcantilever beam, which exhibits good agreement with the simulation. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

... MEMS cantilevers for bio sensing, are adequate to convert biomolecular event into specific measurable quantity. The applications of bio MEMS microcantilevers are pH detection [5], bio-recognition activities analysis and mass detection [1], antigen-antibody reaction [9], triglyceride detection [4], monolayers molecules attogram detection [3], biomolecular analysis such as DNA [2], monomethylmercury detection [6], triaxial tactile measurement [7] and glucose sensing using poly-silicon-based CMOS [8]. The main advantage of microcantilever biosensing is multiagent detection with the help of microcantilever array. ...

In Bio-MEMS applications, low mass loading of biomolecules on rectangular microcantilever beam surface gives negligible deflection at it's free end and poor sensitivity corresponding to the lower concentration of analyte. This paper presents three new microcantilever designs for biosensing, which hold promises for better deflection and higher sensitivity. The proposed designs provide the free end deflection nearly twice as the conventional rectangular beam. The FEM software ANSYS 12.1 is carried out to analyze the deflection of the proposed microcantilever designs.

In this paper we presents a MEMS (Micro-electromechanical System) cantilever based humidity sensor for various applications such as environmental monitoring, electronics, agriculture and biomedical fields. The main focus of this paper is to design, simulate and analyze the performance of MEMS based T shaped micro cantilevers using different sensing materials such as A1+ADw-inf+AD4-2+ADw-/inf+AD4-O+ADw-inf+AD4-3+ADw-/inf+AD4-, Porous Silicon and Poly Silicon. The simulation is done through finite element tool and parameters like the maximum induced stress; deflection and sensitivity of the diaphragms have been analyzed using the software INTELLISUITE version 8.7. The change in humidity element is bending of the micro cantilever that modifies the measured displacement between the substrate and the micro cantilever. This change in displacement gives the measure of amount of water vapor present in that environment. The outcome of these studies can be used to enhance the sensitivity of these devices. Here we observe that the best sensitivity output responses are obtained in the range of 10 RH to 100 RH and also the maximum sensitivity of 21.85 (m/ RH).

Abstract. Cantilever-based sensors have emerged as a promising label free detection technique,
which have been used for high precision mass detection and biomolecular recognition. By surface
functionalization, the cantilever can be modified specific to certain compounds detection. Molecules
adsorbed to one side of the cantilever will deflect the cantilever due to changes in surface stress.
Alternatively, minute mass changes can be detected by monitoring the resonant frequency change of
the cantilever for high-precision mass detections. This work is dedicated to finite element (FE)
3Dstructural modeling of three layers micromechanical sensors in ANSYS 13.0 gives 3D model
which are close to reality mathematical models. Material used in cantilever for different layers are
silicon-dioxide, poly-silicon and nitride. The emphasis of the analysis is put on tile effects of the angle
of inclination of the concentrated force upon the deformed shape, the load-deflection relationship
stresses and strain for further analysis with a greater degree of accuracy. The model we made is three
different model i.e. single layer microcantilevers, three layers microcantilever with same height and
three layers with different height. In three layer the centre layer i.e. second layer, is piezoresistive
layer that helps to calculate Characteristics i.e. deflection, deformation, stress and strain in the
cantilever for the given applied force that can we used for future analysis for the detection of
biomolecules in various biosensing application. Finally the comparison of all the three different
model of cantilever according to their characteristics.

A method for calculating the surface stress associated with the deflection of a micromechanical cantilever is presented. This method overcomes some of the limitations associated with Stoney’s formula by circumventing the need to know the cantilever’s Young’s modulus, which can have a high level of uncertainty, especially for silicon nitride cantilevers. The surface stress is calculated using readily measurable cantilever properties, such as its geometry, spring constant, and deflection. The method is applicable to both rectangular and triangular cantilevers. A calibration of the deflection measurement is also presented. The surface stress measurement is accurate to within 4%–7%.

In this paper an analysis of influence of three type of damping on free vibration of elastic systems is presented. Linear viscous, nonlinear viscous and dry friction damping were considered. Special emphasis was on determining of critical damping value for all of three types of considered damping cases. Also, analysis of logarithmic decrement of amplitudes, evaluation and comparison logarithmic decrement for considered damping types is presented. For all types of damping, same features of system were used and then analysed. Since some of types of damping couldn’t be solved in closed form, numerical method was used. In this case, forth-order Runge-Kutta method is used for solving damping proportional to squared velocity of motion. Most important conclusion is that only system with linear viscous damping could have critical damping value.

This article uses finite element design for optimization of piezoresistive Si covered SiO2 microcantilevers. The maximum resistance changes were systematically investigated by varying piezoresistor geometries and doping concentration. Our simulation results show that both cantilever deflection displacement and ΔR/R change decrease when the thickness of piezoresistors increases; the highest sensitivity can be obtained when the piezoresistor length is approximately 2/5 of the SiO2 cantilever length; increase of both Si width and leg width result in decrease in cantilever deflection and sensitivity; the sensitivity of cantilevers with lower doping concentrations is more significant than those with higher doping concentrations. Temperature control is critical for thin piezoresistor in lowering the S/N ratio and increasing the sensitivity.

The mechanical design and optimization of piezoresistive cantilevers for biosensing applications is studied using finite element analysis. The change of relative resistivity of piezoresistive microcantilevers is analyzed in the presence of the chemical reaction at the receptor surface under the condition of oscillating flow. Chemo-mechanical binding forces have been analyzed in order to understand issues of saturation over the cantilever surface. Furthermore, the optimum design using finite element modeling is achieved by modifying the factors pertaining to the geometry of the microcantilevers under the condition of bio-binding. The introduction of stress concentration regions (SCRs) during cantilever fabrication has been discussed, which greatly enhances the detection sensitivity through increased surface stress. Finally, the optimum SCR modified 'C' piezocantilever system for biosensing is designed and the optimal parameters are set for high sensitivity.

We present a mathematical model for the dynamics of an electrostatically actuated micro-cantilever. For the common case of cantilevers excited by a periodic voltage, we show that the underlying linearized dynamics are those of a periodic system described by a Mathieu equation. We present experimental results that confirm the validity of the model, and in particular, illustrate that parametric resonance phenomena occur in capacitively actuated micro-cantilevers. We propose a system where the current measured is used as the sensing signal of the cantilever state and position through a dynamical observer. By investigating how the best achievable performance of an optimal observer depends on the excitation frequency, we show that the best such frequency is not necessarily the resonant frequency of the cantilever.

We report an equivalent circuit model for MEMS (microelectromechanical systems) electrostatic actuator using open-source circuit simulator Qucs (quite universal circuit simulator). Electrostatic force, equation of motion, and Kirchhoff's laws are implemented by using the EDD (equation defined device) function of Qucs. Mathematic integral operation in the equation of motion is interpreted into electrical circuits by using an ideal electrical capacitor that read input signal as current and returns accumulation result in terms of voltage. Seamless multi-physics mixed signal simulation between micro mechanics and electronics has become possible on the single platform of the circuit simulator.

Analysis of an Electrostatic Microactuator with help of Matlab/simulink: transient and frequency characteristics

- D O Francais

Design and Analysis of a high sensitive Microcantilever Biosensor for Biomedical Applications

- C C Mohd Zahid
- Ansari