Modelling and Fabrication of a Multi-Modal Highly Sensitive Pressure Sensor

Abstract

Flexible and skin mountable wearable health monitoring devices have gained much attention in recent years due to their non-invasive approach to continuous monitoring of weak human physiological signals. With applications such as pulse detection and electronic skin, the potential usage of the highly sensitive pressure sensor is more significant than before. In general, ultra-sensitive pressure sensors can be categorized by the operation mechanism into piezoresistive, capacitive, triboelectric, and piezoelectric sensors. Because all these mechanisms require a flexible substrate for their process, combining different sensing mechanisms leads to one multi-mechanism sensor with compounded advantages and diminished shortcomings. In this study, a multimodal sensor (combining piezoresistive, capacitive, and strain gauge modes of operation) with optimized parameters for precise monitoring of arterial pulse waveform has been proposed to allow detection of not only the pulse but also possible irregularities in its waveform that can be potentially the harbingers of various medical conditions. Finite element analysis was employed to establish the design rules for a highly sensitive piezoresistive sensor and also design rules for a micropatterned dialectic layer were developed and after the fabrication of both sensors, they were merged to form a compact multi-mechanism sensing platform. Moreover, fabrication of breathable polymeric substrate has been accomplished by methods such as electrospinning, sacrificial template, and electrostatic spray deposition to ensure long term comfortable wearability of the device. After the fabrication, this capacitive sensor was used to detect the human pulse from the wrist. Also, using bi-polar electrochemistry porous graphene was deposited on the polymeric foundation as the conductive sensing material for the piezoresistive sensor.Furthermore, the results form modelling showed that smaller feature size, lower number density, and a pyramid angle of about 60 degrees of microfeatures improve the sensitivity of the sensor. And finally, the fabrication of the multi-mechanism sensor followed the standard microfabrication techniques including photolithography and transfer printing method to integrate heterogeneous elements into the sensor. The detailed results will be discussed during the presentation.