Designing comfortable-to-use wearable strain sensors with thermal management through radiative cooling function

In this study, we designed a hybrid smart sensor capable of self-radiative cooling while exhibiting a high strain sensitivity. To achieve high cooling efficiency and sensitivity simultaneously, the optical, electronical, chemical, and mechanical properties of each material in the hybrid smart sensor were engineered. The sensor was composed of polydimethylsiloxane (PDMS), an Ag film, and Ag nanoparticles (NPs), which acted as mid-infrared emitters/encapsulators, a visible reflector/strain sensor, and an adhesion/sensitivity enhancer, respectively. Ligand-exchange-based chemical and mechanical treatments of the Ag NPs and microcrack formation improved the sensitivity of the sensor, and the PDMS encapsulator increased the stability and cooling efficiency, effectively dissipating the heat generated during the sensor's operation to the external environment. Upon attaching the hybrid sensor to human skin and robot hands, it effectively detected the motion of objects and lowered the temperature. The proposed hybrid smart sensor is an ecofriendly and energy-sustainable wearable sensor system that can be applied in human-motion detection and robotics applications. We believe that our comfortable wearable device does not induce thermal discomfort in users.