Stretchable and wearable polymeric heaters and strain sensors fabricated using liquid metals

• Published in: Sensors and actuators. A. Physical. Vol. 355; p. 114317
• Main Authors: Kim, Sihyun, Saito, Masato, Wei, Yuwen, Bhuyan, Priyanuj, Choe, Minjae, Fujie, Toshinori, Mondal, Kunal, Park, Sungjune
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 01.06.2023; Elsevier
• Subjects: Liquid metal; OTHER INSTRUMENTATION; Strain sensor; Stretchable and soft electronics; Wearable polymeric heater; LM@CIP; HCl; Liquid metal; Stretchable and soft electronics; LMs; Strain sensor; WEDs; CIPs; Wearable polymeric heater; EGaIn; LMWs; PET
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2023.114317

Wearable electronic devices (WEDs) are receiving significant attention because of the increasing interest in soft robotics, electronic skin, and wearable sensors. Liquid metals (LMs) are compelling for WEDs owing to their metallic conductivity, fluidic nature, and low toxicity. Herein, we fabricated stretchable and soft WEDs using LM (eutectic gallium-indium alloy) wires (LMWs) patterned via force wetting through custom-made stencils on an elastic substrate. LMWs can generate thermal energy via Joule heating upon current application and deliver it to the substrate, resulting in wearable polymeric heaters. The LM mixed with carbonyl iron particles (CIPs) can also be patterned while preserving fluidic behavior. The degree of thermal energy generated through the LMWs can be manipulated as a function of the CIP concentration in the LM and geometrical factors of the electrode patterns, i.e., width and length. An elastic film patterned with LMWs attached to the human body exhibits changes in the effective electrical resistance depending on applied strain, demonstrating potential as a wearable strain sensor. This LM utilized WED that can generate thermal energy upon current application through the LMWs and detect the bodily motion has significant potential for application in wearable thermotherapy, electronic skin, and soft sensors. [Display omitted] •Soft and stretchable wearable heaters and strain sensors utilizing liquid metal electrode.•Wearable devices exhibiting ultrasoftness (116 kPa), ultrastretchability (>1300 %) and strong adhesion to the surfaces.•Wearable devices exhibiting ultrasoftness (Young’s modulus of 116 kPa), ultrastretchability (elongation at break of > 1300 %) and strong adhesion to the surfaces.•Wearable devices generating thermal energy by Joule-heating through liquid metal wires.•Liquid metal wires changing electrical resistance by deformation upon strain.