B. D. Pant

Design and development of cantilever-type MEMS based piezoelectric energy harvester

Vibration energy harvesting is gaining attention due to abundance of vibration energy at most places and ability to generate power MEMS devices from microwatts to few millwatts. Piezoelectric energy harvesters are the most suitable for vibration energy harvesting due to simplicity in design, operation and fabrication in MEMS technology. Cantilever fixed from one end and seismic mass on the free end is used to harvest energy which is modeled as spring mass damper system responding to a single frequency. Wideband frequency operation for the energy harvester must be ensured so that power is harvested for a range of frequency. In this paper cantilever array with variable length from 2000 μm to 2200 μm is designed and simulated at a boundary load of 1 bar pressure to achieve a wideband frequency operation from 681 Hz to 1215 Hz.

Design and Simulation of Bulk Micromachined Accelerometer for Avionics Application

In the present paper, the design and simulation of a MEMS polysilicon piezoresistive based bulk micromachined accelerometer for avionics application i.e. ± 10g has been presented. The maximum acceleration this design can bear is ± 50g. The accelerometer design presented in this paper consists of a trapezoidal shaped proof-mass suspended by four flexures. The piezoresistors are placed at the maximum stress locations on the beams, worked out through simulation tool COMSOLTM Multiphysics. The optimum size of the sensor structure, stress, displacement of proof-mass and output voltage are analytically calculated. For 10g acceleration the relative resistance change is 3.66 × 10− 3 and output voltage is 18.29 mV. Sensitivity of this accelerometer is 0.366 mV/V/g. A comparison of the analytical and simulation results is also presented.

Sensitivity and non-linearity study and performance enhancement in bossed diaphragm piezoresistive pressure sensor

This paper describes a comparative study of sensitivity and non-linearity of conventional and bossed diaphragm piezoresistive pressure sensor along with a performance enhanced design. The proposed structures take into consideration corner compensation to avoid distortion of the mesa structure during fabrication of bossed diaphragm structure using wet bulk micromachining. Optimum piezoresistors locations are calculated with the help of simulations carried out using finite element method (FEM) based tool COMSOL© Multiphysics. Since the sensitivity and non-linearity of conventional and bossed diaphragm structures showed a linear trend, empirical formulae are proposed using linear fit for quick and approximate calculation of sensitivity and non-linearity for a particular sensor structure. It is observed that high stress regions are also present near the boss - diaphragm interface and hence a design with piezoresistors placed at these regions is also proposed. This design is found to be enhancing the performance of piezoresistive pressure sensor compared to the conventional piezoresistor placement.

Fabrication and characterization of pressure sensor, and enhancement of output characteristics by modification of operating pressure range

Pressure microsensors are very frequently used for applications encompassing a wide range of operating pressure ranges. However, it is possible to use the same pressure sensor for different operating ranges (in a limited range) with satisfactory performance. In this work, we report the possibility of using a single sensor for different pressure ranges. Operating the sensor at a lower pressure range not only offers flexibility of usage but also enhances output performance in terms of sensitivity and linearity. The concept is demonstrated using a pressure sensor with implanted polysilicon piezoresistors and bulk micromachined diaphragm fabricated using a standard process. The characterization data of the sensor is analyzed for three pressure ranges (10 Bar, 20 Bar and 30 Bar). The results show that modifying the full scale pressure of operation from 30 to 10 Bar increases the sensitivity from 6.03 mV/Bar to 6.58 mV/Bar. The non-linearity is also reduced by an order of magnitude from 3.89 % to 0.33 %.