Numerical study on the influence of buried oxide layer of SOI wafers on the terminal characteristics of a micro/nano cantilever biosensor with an integrated piezoresistor

Biomed. Phys. Eng. Express

2017

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In recent times, catheters with integrated transducers have been extensively investigated in the field of biomedical engineering, especially for use in in vivo neonatal intensive care systems. An integral module of such systems is a blood pressure sensor that must fulfill the competing requirements of high sensitivity and small area. Typically, microelectromechanical systems-based membrane structures with integrated piezoresistors are used to realize such miniaturized blood pressure sensors. Conventionally, the electromechanical transduction of membrane deformation into an equivalent electrical signal is accomplished by piezoresistors connected in a fully active Wheatstone bridge configuration. However, such a configuration requires a large area for the placement of piezoresistors and layout of interconnects. Even though piezoresistors connected in a half-active Wheatstone bridge configuration overcome the area constraint, such an arrangement still suffers from reduced electrical sensitivity. In this paper we propose a novel three-terminal single-element piezoresistor membranebased miniaturized blood pressure sensor for less than 1 French catheter application. Design and optimization of the sensor is performed using numerical simulations to satisfy the competing requirements of high sensitivity, low structural non-linearity and high mechanical stability. Simulations are carried out to optimize the piezoresistor position, piezoresistor doping concentration and relative dimensions of the piezoresistor and the membrane. Results depict that sensor with a die size of 175 × 150 × 50 μm 3 results in an electrical sensitivity of 14.03 μA A -1 mmHg -1 . Finally, a set of design guidelines are outlined for optimizing the performance of three-terminal piezoresistor-based blood pressure sensors.

Section: Validation With Experimental Resultsmentioning

confidence: 99%

Design and optimization of a three-terminal piezoresistive pressure sensor for catheter based in vivo biomedical applications

Meena

Biomed. Phys. Eng. Express

2017

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“…The sensor response is evaluated based on the sensitivity ratio (υ), i.e. the ratio of electrical sensitivity (ΔR/R|σ s ) to thermal sensitivity (ΔR/R| TCE+TCP+TCR ) devised elsewhere [35]. Typically, piezoresistive cantilever sensors are operated in a WSB configuration with one sensing cantilever and one reference cantilever operated in differential mode and the other two piezoresistors formed by passive resistors near the cantilever mechanical base region.…”

Section: Theory and Modelingmentioning

confidence: 99%

Optimization of a nano-cantilever biosensor for reduced self-heating effects and improved performance metrics

J. Micromech. Microeng.

2018

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Over the last decade, surface stress-based piezoresistive cantilever biosensors have been extensively explored as a potential alternative for conventional clinical diagnostic techniques. The design of piezoresistive cantilever sensors is a complex multi-variable problem which involves the interplay between the thermal, electrical and mechanical design aspects of their constituent materials and geometry. Even though the literature includes examples where researchers have devised designs of piezoresistive cantilever biosensors, a majority of them have focused primarily on improving the electrical sensitivity by either dimensional optimization or material changes of their constituent layers. However, there are two important aspects of the sensor design which have been seldom addressed: (i) the negative impact of the transverse section of the U-shaped piezoresistor on the electrical sensitivity, and (ii) thermal drift in the output characteristics of the sensor. Although a few researchers have focused on the aforementioned factors, they have analysed them independently without considering their interdependence and cumulative impact on the sensor performance. In this paper, we devise a dual material multi-part U-shaped piezoresistor comprised of two p-type single crystalline silicon longitudinal sections and a p-type polysilicon transverse section. Evaluation of the proposed piezoresistor is performed in two stages using a finite element method-based numerical tool. In the first stage, the performance of the sensor with the multi-part piezoresistor is compared with the reported piezoresistors available in the literature. In the second stage, a comprehensive investigation of the multi-part piezoresistor is carried out to maximize the sensor performance. Results show that, compared to a conventional U-shaped piezoresistor, the proposed piezoresistor achieves improvement in the sensitivity ratio by 8.12 times.

“…More specifics of the modeling technique and details of initial deflection of the cantilever as a function of environmental temperature is reported elsewhere. 36 In order to mimic the target-receptor interactions, top surface of the cantilever is applied with a compressive stress of magnitude 5 E-3N/m, which is a typical in antigen-antibody interactions on Au surface. 37 For validating the modeling approach we have compared our computational results with the experiments reported in the literature.…”

Section: A Simulation Modelmentioning

confidence: 99%

“…The factor υ is obtained by computing the ratio of target-receptor interactions induced surface stress to self-heating induced changes in ∆R/R. 36 The factors TCP, TCR and TCE contribute to the thermal drift of sensor output. Typically, a piezoresistive cantilever biosensor is connected to one arm of a Wheatstone bridge (WSB) with another reference cantilever operated in differential mode.…”

Section: Effect Of Piezoresistor Width On Sensitivity Ratiomentioning

confidence: 99%

In silico modeling and investigation of self-heating effects in composite nano cantilever biosensors with integrated piezoresistors

2017

AIP Advances

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Over the years, piezoresistive nano cantilever sensors have been extensively investigated for various biological sensing applications. Piezoresistive cantilever sensor is a composite structure with different materials constituting its various layers. Design and modeling of such sensors become challenging since their response is governed by the interplay between their geometrical and constituent material parameters. Even though, piezoresistive nano cantilever biosensors have several advantages, they suffer from a limitation in the form of self-heating induced inaccuracy which is seldom considered in design stages. Although, a few simplified mathematical models have been reported which incorporate the self-heating effect, several assumptions made in the modeling stages result in inaccuracy in predicting sensor terminal response. In this paper, we model and investigate the effect of self-heating on the thermo-electro-mechanical response of piezoresistive cantilever sensors as a function of the relative geometries of the piezoresistor and the cantilever platform. Finite element method (FEM) based numerical computations are used to model the target-receptor interactions induced surface stress response in steady state and maximize the electrical sensitivity to thermal sensitivity ratio of the sensor. Simulation results show that the conduction mode of heat transfer is the dominant heat transfer mechanism. Furthermore, the isolation and immobilization layers play a critical role in determining the thermal sensitivity of the sensor. It is found that the shorter and wider cantilever platforms are more suitable to reduce self-heating induced inaccuracies. In addition, results depict that the piezoresistor width plays a more dominant role in determining the thermal drift induced inaccuracies compared to the piezoresistor length. It is found that for surface stress sensors at large piezoresistor width, the electrical sensitivity to thermal sensitivity ratio improves.