Wearable sensors developed using a novel plastic metal material

Plastic metal (PM) is a highly advanced material with numerous advantages, such as the convenience associated with its shaping and coating, precise pattern definitions, and convenience for recycling, thereby making it an excellent material for soft electronics. PM material has the ability to be plastically molded into arbitrary deformation by external forces, but it can remain intact even under large deformations as long as PM is encapsulated in polydimethylsiloxane (PDMS). This study aims to verify the feasibility of its application to wearable soft sensors, including flexible and pressure sensors. The experimental results show that with the use of synthetic conditions at a 4:1 mass ratio of liquid metal (LM) to quartz powder, PM yields the best characteristics. Apart from the good electrical conductivity (with a resistivity of 3.29 × 10^− 5 Ω-cm), it also has better coating ability, plasticity, and film formability. The developed flexible sensor can sense bending angle changes in the range of 0°–180° with stable performance and with an average gauge factor $\text{G}{\text{F}}_{\text{avg}}$ of 2.616. With regard to the pressure sensor, when the pressure range is from 0 to 40 psi (≈ 275.79 kPa), the resistance change rate shows a slightly concave-down quadratic curve, while the pressure is greater than 40 psi, the characteristic is a linear relationship with an average slope of 0.022. Furthermore, real-life verification of the two sensors based on experiments shows that their performances are stable and repeatable. Therefore, this study has confirmed that the sensors made of PM can be practically applied to the development of wearable sensors and has emphasized the potential for their use in dynamic sensing applications in humans or robots.