Piezoresistive stretchable strain sensors with human machine interface demonstrations

Stretchable strain sensors are important elements in flexible and skin-mountable electronics typically fabricated using semiconductor materials in cleanroom-based manufacturing processes. This work demonstrates piezoresistive strain sensors with both strain and pressure sensing capabilities by a cost-effective and versatile process utilizing a laser patterning, graphite conversion, and polymeric transfer process. The resulting sensing systems exhibit high gauge factor of 37 and pressure sensitivity of 0.088kPa-1 with high sustainable strain up to 70%. These exceptional performances are explained and observed by deforming the sensor under an in-situ SEM to show self-healing characteristics of films under large deformations. The highly sensitive strain sensors have been shown in human interface demonstrations, such as measuring the physiological signal of the human pulses, finger pressure and bending of fingers as well as assisting a robotic arm for gripping and releasing operations.