Design and development of strain gauge for biomedical applications: State of the art review

Materials that characteristically respond to mechanical stimulus are utilized in a wide variety of engineering applications as strain gauges. The response can be produced as a change in resistance or a change in capacitance. Constantan was initially utilized in strain gauges and exhibited a gauge factor (GF) of 2. With the development of fabrication techniques, new materials are correspondingly utilized in strain gauges that revealed a GF higher than 2. However, a review pertaining to the latest materials utilized in strain gauges is absent. Therefore, in this review article, strain gauges utilizing metallic, polymer, and ceramic-based materials were investigated by evaluating their fabrication method, characterization in numerous testing conditions, gauging their sensitivity and the parameters influencing the same, and proposing a real-world biomedical application based on the sensor properties ranging from monitoring of orthopedics, knee laxity, heartbeat, and mechanical properties of implants and prosthetics, to stretchable and wearable sensors for e-skin and exoskeletons.