Fabrication of MEMS piezoresistive accelerometer for human gait analysis using laser micromachining

Abstract

Gait analysis measurement is a method to access and identify gait events and the measurements of motion parameters involving the lower part of body. This significant method is widely used in rehabilitation, sports, as well as health diagnostic towards improving the quality of life. However, it is not a routine practice due to the costs involved in producing the mechanism and using gait labs. Alternatively, inertial sensors such as microcantilever accelerometer can be used in the development of cheap and wearable gait analysis systems. Human stride segmentation measurement based on micro-accelerometer cantilever is used in the study of the lower limb movement patterns that include walk, jump and run; and the measurements of the motion parameters. A complete system consists of a fabricated sensor, a Wheatstone bridge circuit and a signal amplifier tailored for real-time stride analysis measurement is proposed. As such, this thesis reporting the requirement of research studies, design, fabrication development and analysis of a MEMS acceleration sensor for gait movement measurement. Current conventional method requires high combination of dry and wet process in structuring sensor formations. A novel method for accelerometer sensor fabrication is by using laser micromachining in order to develop a simple way in realizing the sensor formation. Polysilicon doped boron material is uses as sensing material for sensor. Experimental work clearly reveals that a linearity measurement of acceleration is achievable using the fabricated sensors. The sensors also demonstrated good signal magnitudes for efficient diagnosing of movement given. This study allows us to optimize the requirements of hard-mask and fabrication process steps by reduction of 30% and 25% steps respectively. In the general framework, the research activities is focused towards development of piezoresistive cantilever formation by using laser micromachining for fast fabrication development for real life gait and stride segmentation measurement applications.