Design and Simulation of a Novel Biomechanic Piezoresistive Sensor With Silicon Nanowires

2010

We report an actuation/detection scheme with a top-down nano-electromechanical system for frequency shift-based sensing applications with outstanding performance. It relies on electrostatic actuation and piezoresistive nanowire gauges for in-plane motion transduction. The process fabrication is fully CMOS compatible. The results show a very large dynamic range (DR) of more than 100dB and an unprecedented signal to background ratio (SBR) of 69dB providing an improvement of two orders of magnitude in the detection efficiency presented in the state of the art in NEMS field. Such a dynamic range results from both negligible 1/f-noise and very low Johnson noise compared to the thermomechanical noise. This simple low-power detection scheme paves the way for new class of robust mass resonant sensor.

Microelectronics Journal, 2006

The CMOS compatible bulk micromachined piezoresistive accelerometer presented in this paper consists of four flexures supporting a proof mass. Four pairs of boron-diffused piezoresistors are located at maximum stress points on the flexures near the proof mass and frame ends. Because of the opposite nature of stress at the two ends, these piezoresistors can be connected to form a Wheatstone bridge such that the off-axis responses are practically cancelled while the on-axis (along perpendicular to proof mass) response is maximized. The device is simulated using CoventorWare. In the fabrication process, dual-doped TMAH solution is used for wet anisotropic etching. The novelty of this etching process is that the bulk micromachining can be performed after aluminum metallization. The etched surface is also smooth. The fabrication is thus CMOS compatible. The accelerometer exhibits good linearity over 0-10 g.

2009

This paper presents the novel synthesis design of a three-degree of freedom silicon piezoresistive accelerometer. The purpose of this novel synthesis design is to achieve the high performance device. The design synthesis has been performed based on considerations of mechanical and electronics sensitivities, noise and thermal effects, respectively. The mechanical sensitivity is optimized due to combination of a FEM software and a MNA one. The electronics sensitivity, noise and thermal effect can be determined by thermal, mechanical and piezoresistive coupled-field simulations. The dimension of sensor is as small as 1.5 mm 2 , so it is suitable for many immerging applications.

International Journal of Automotive Science And Technology

Wearable flexible piezoresistive pressure sensors hold wide-ranging potential in human health monitoring, electronic skin, robotic limbs and other human-machine interfaces. Out of the most successful recent efforts for arterial pulse monitoring are sensors with micro-patterned conductive elastomers. However, low current output signal (typically in the range of nanoamperes), bulky and expensive measurement equipment for useful signal acquisition inhibits their wearability. Herein, through finite element analysis we establish the design rules for a highly sensitive piezoresistive pressure sensor with output that is high enough to be detectable by simple and inexpensive circuits to ensure wearability. We also show that out of four frequently reported micro-feature shapes in micro-patterned piezoresistive sensors, micro-dome and micro-pyramid yield the highest sensitivity. Furthermore, investigations of different conductivity values of micro-patterned elastomers found that coating the e...

2011

N-type hydrogenated nanocrystalline silicon thin film piezoresistors, with gauge factor-28, were deposited on rugged and flexible polyimide foils by Hot-wire chemical vapor deposition using a tantalum filament heated to 1750ºC. The piezoresistive response under cyclic quasistatic and dynamical (up to 100 Hz) load conditions is reported. Test structures, consisting of microresistors having lateral dimensions in the range from 50 to 100 µm and thickness of 120 nm were defined in an array by reactive ion etching. Metallic pads, forming ohmic contacts to the sensing elements, were defined by a lift-off process. A readout circuit for the array consisting in a mutiplexer on each row and column of the matrix is proposed. The digital data will be processed, interpreted and stored internally by an ultra low-power micro controller, 2 also responsible for the communication of two-way wireless data, e.g. from inside to outside the human body.

Sensors and Actuators A …, 2005

This paper presents the design and development of a silicon-based three-axial force sensor to be used in a flexible smart interface for biomechanical measurements. Normal and shear forces are detected by combining responses from four piezoresistors obtained by ion implantation in a high aspect-ratio cross-shape flexible element equipped with a 525 m high silicon mesa. The mesa is obtained by a subtractive dry etching process of the whole handle layer of an SOI wafer. Piezoresistor size ranges between 6 and 10 m in width, and between 30 and 50 m in length. The sensor configuration follows a hybrid integration approach for interconnection and for future electronic circuitry system integration. The sensor ability to measure both normal and shear forces with high linearity ( ∼ =99%) and low hysteresis is demonstrated by means of tests performed by applying forces from 0 to 2 N. In this paper the packaging design is also presented and materials for flexible sensor array preliminary assembly are described.

IEEE Transactions on Electron Devices, 1988

This paper reports a new combination of micromachining techniques with the piezojunction effect in bipolar transistors for the realization of a uniaxial accelerometer (Le., with virtually no crosssensitivity). The piezojunction phenomenon quantifies the changes in transistor characteristics under mechanical stress. Experiments revealed an excellent linear relationship between Vsr change and stress in the base-emitter junction. This new approach enables the performance of stress measurements at lower power consumption to, e.g., resistive bridge structures. Selective etching techniques are used to micromachine a seismic mass in the center of the chip, which is suspended by four beams. Emphasis was put in the realization of high resonant frequencies in every axis. Also, by using an electrical cross-coupling technique of the four piezojunction transistors, transverse sensitivity can be reduced to below 1 percent. The accelerometers have been developed for airborne and robotic applications and measure less than 4 x 4 mm. They are designed for an acceleration range between 1 and 100 g, depending on the processing parameters, and a resolution of better than four decades.

IOSR Journal of Engineering, 2013

This paper presents a design and development of a high-performance silicon piezoresistive MEMS accelerometer, with a finite element analysis (FEA) and low cross-axis sensitivity. Finite element analysis is used to simulate electro statically actuated piezoresistive accelerometer operating under dc conditions .The designs presented in this paper consist of a square shaped proof mass with flexures supporting it. Due to of the opposite nature of stress at two ends, these piezoresistors can be connected to form a Wheatstone bridge so that the cross-axis responses are practically reduced .The piezoresistors are placed near the proof mass and frame ends on the flexure. The simulations show the von Misses stress, displacement, Eigen frequency plot, voltage distribution and temperature change in the piezoresistors using COMSOL 4.3 Multiphysics.

IEEE/ASME Journal of Microelectromechanical Systems, 2006

While micromachined accelerometers are widely available and used in various applications, some biomedical applications require extremely small dimensions (<mm) or mass (<mg) that cannot be fulfilled with commercially available accelerometers. In this work, we present a fully packaged piezoresistive accelerometer that has the smallest dimension (0.034mm3) ever published. We achieve miniaturization by using a film encapsulation technique with a thick