Finite Element Method-based Design and Simulations of Micro-cantilever Platform for Chemical and Bio-sensing Applications (original) (raw)
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Simulation and design of piezoelectric microcantilever chemical sensors
2005
This paper presents an analytical modeling of a piezoelectric multi-layer cantilever used as a micro-electro-mechanical-system (MEMS) chemical sensor. Selectively coated microcantilevers have been developed for highly sensitive chemical sensor applications. The proposed piezoelectric chemical sensor consists of an array of multi-layer piezoelectric cantilevers with voltage output in the millivolt range that replaces the conventional laser-based position-sensitive detection systems. The sensing principle is based upon changes in the deflection induced by environmental factors in the medium where a microcantilever is immersed. Bending of the cantilever induces the potential difference on opposite sides of the piezoelectric layer providing an information signal about the detected chemicals. To obtain an application specific optimum design parameters and predict the cantilever performance ahead of actual fabrication, finite element analysis (FEM) simulations using CoventorWare (a MEMS design and simulation program) were performed. Analytical models of multi-layer cantilevers as well as simulation concept are described. Both mechanical and piezoelectric simulation results are carried out. The cantilever structures are analyzed and fabrication process steps are proposed.
Journal of Physics D: Applied Physics, 2015
Microcantilever platforms with integrated piezoresistors have found versatile applications in the field of clinical analysis and diagnostics. Even though treatise encompasses numerous design details of the cantilever based biochemical sensors, a majority of them focus on the generic slender rectangular cantilever platform mainly due to its evolution from the atomic force microscope (AFM). The reported designs revolve around the aspects of dimensional optimization and variations with respect to the combination of materials for the composite structure. In this paper, a triangular cantilever platform is shown to have better performance metrics than the reported generic slender rectangular and the square cantilever platforms with integrated piezoresistors for biochemical sensing applications. The selection and optimization of the triangular cantilever platform is carried out in two stages. In the first stage, the preliminary selection of the cantilever shape is performed based on the initial design obtained by analytical formulae and numerical simulations. The second stage includes the geometrical optimization of the triangular cantilever platform and the integrated piezoresistor. The triangular cantilever platform shows a better performance in terms of the figure of merit (FoM), ψ Δ = R R f (/) 0 2 and the measurement bandwidth. The simulation results show that the magnitude of ψ of the triangular platform is 77.21% and 65.64% higher than that of the slender rectangular and the square cantilever platforms respectively. Moreover, the triangular platform exhibits a measurement bandwidth that is 70.91% and 2.04 times higher than that of the slender rectangular and square cantilever structures respectively. For a better understanding of the 2D nature of the stress generated on the cantilever platform due to the surface stress, its spatial profile has been extracted and depicted graphically. Finally, a set of design rules are provided for optimizing the triangular cantilever platform and piezoresistor dimensions in terms of the electrical sensitivity and the mechanical stability for biochemical sensing applications.
Modeling of Piezoresistive Cantilevers for Chemical Sensing
International Journal of Engineering Applied Sciences and Technology
This paper presents and analytical model to provide good results for cantilevers with point load at free end and to describe the micro cantilevers with surface stress. It has been shown that the width of the cantilever has to be increased to optimize the sensitivity. The placement of the piezoresistor was found to be in the centre of the cantilevers clamped end and the area of the piezoresitor should be minimized.
This paper considers the use of surface stress based sensors as bio chemical sensors. In principle, adsorption of bio chemical species on a functionalized surface of a microfabricated cantilever will cause surface stress and consequently the cantilever bends. Piezoresistive actuation of a micro cantilever induced by bio molecular binding such as DNA hybridization and antibody-antigen binding is an important principle. This paper presents design and simulation studies of gold coated Piezoresistive cantilever used as Micro Electro Mechanical System (MEMS) based biosensor for the detection of Low Density Lipoproteins (LDL). This paper uses Finite Element Method (FEM) to obtain the performance of piezoresistive microcantilever sensor by optimizing the geometrical dimensions of both cantilever and piezoresistor. A 200µm X 100µm X 1µm Silicon cantilever integrated with 0.3 µm thick Silicon piezoresistor, with 1µm of gold coating was used. The sensor performance was measured on the basis of displacement sensitivity and surface stress sensitivity. The sensor sensitivity was investigated by varying cantilever thickness as well as piezoresistor thickness and its width. Simulation results show that the cantilever sensitivity is good when cantilever, piezoresistor thickness and piezoresistor width are at minimum.
Engineering Mechanics ..., 2024
The focus of this research project is to enhance cantilever beam designs for biosensing applications by including Stress Concentration Regions (SCRs). The stress distribution across several cantilever beam designs was determined by simulating them using COMSOL Multiphysics. The earliest designs were developed utilizing Polyvinylidene fluoride (PVDF) to showcase improved sensitivity for mechanical detection without the need for labels in biosensor applications. The analysis of cantilever beams involves the examination of their eigenfrequency and stationary behavior in the context of piezoelectric effect physics. An analysis is conducted on several cantilever beam structures to determine the most appropriate one. In this analysis, the various beams are exposed to an identical mechanical force, and their respective displacements, potential voltage, von Mises stress, and eigenfrequencies are examined.
Design and Analysis of Microcantilevers for Biosensing Applications
Journal of the Association for Laboratory Automation, 2003
W e have analyzed the detection of microcantilevers utilized in biosensing chips. First, the primary deflection due to the chemical reaction between the analyte molecules and the receptor coating, which produces surface stresses on the receptor side is analyzed. Oscillating flow conditions, which are the main source of turbulence in cantilever based biosensing chips, are found to produce substantial deflections in the microcantilever at relatively large frequency of turbulence. Then mechanical design and optimization of piezoresistive cantilevers for biosensing applications is studied. Models are described for predicting the static behavior of cantilevers with elastic and piezoresistive layers. Chemo-mechanical binding forces have been analyzed to understand issues of saturation over the cantilever surface. Furthermore, the introduction of stress concentration regions during cantilever fabrication has been discussed which greatly enhances the detection sensitivity through increased surface stress, and novel microcantilever assemblies are presented for the first time that can increase the deflection due to chemical reaction. Finally an experiment was made to demonstrate the shift of resonant frequency of cantilever used as biosensor. The relation between resonant frequency shift and the surface stress was analyzed.
Fabrication of piezoresistive microcantilever using surface micromachining technique for biosensors
2005
A microcantilever-based biosensor with piezoresistor has been fabricated using surface micromachining technique, which is cost effective and simplifies a fabrication procedure. In order to evaluate the characteristics of the cantilever, the cystamine terminated with thiol was covalently immobilized on the gold-coated side of the cantilever and glutaraldehyde that would be bonded with amine group in the cystamine was injected subsequently. This process was characterized by measuring the deflection of the cantilever in real time monitoring. Using a piezoresistive read-out and a well-known optical beam deflection method as well, the measurement of deflection was carried out. The sensitivity of piezoresistive method is good enough compared with that of optical beam deflection method.
International Journal of Engineering Development and Research, 2014
1 Research scholar, 2 Professor & HOD 1 Electronics Department Sathyabama University, Chennai, India 2 I&C Department, SRM University,Chennai,India vikas_selvan@yahoo.co.in ________________________________________________________________________________________________________ Abstract—This paper deals with a biosensor using a micro fabricated array of micromechanical cantilevers. This biosensor is used to detect tuberculosis. The sensor consists of antibody layer immobilized onto gold-coated cantilevers and interacts with antigen. The patient blood sample is placed on the cantilever surface. If the sample contains disease causing antigen, immobilized antibody binds with the antigen. This antigen antibody binding causes increase in surface stress. The addition of mass due to antigen antibody binding involved in this process causes the cantilever to bend. The deflection of these cantilever beams can be detected using various techniques like piezoresistive, piezoelectric or capacitive...