Multifunctional ultrastretchable and ultrasoft electronics enabled by uncrosslinked polysiloxane elastomers patterned with rheologically modified liquid metal electrodes: Beyond current soft and stretchable electronics

• Ultrastretchable and ultrasoft electronics enabled by uncrosslinked polysiloxane elastomers patterned with liquid metal electrode. • The electronic devices exhibiting ultrastretchability (>4,000%), ultrasoftness (<0.1MPa) and characteristic surface adhesion. • Rheologically modified liquid metal electrodes patterned by forced-wetting. • The electronic devices utilized for wearable strain sensors, soft heating pad and mountable energy-harvesting device. The exploration and identification of new polymeric materials that can serve as components for soft and stretchable electronic devices complying with various demands such as ultrasoftness, ultrastretchability and skin conformality, has attracted much attention. In this study, a commercially available silicone elastomer, ExSil 100, which exhibits ultrastretchability, ultrasoftness and characteristic surface adhesion due to uncrosslinked highly entangled polymeric chains, has been used for the first time to fabricate soft and stretchable electronics. Liquid metals are compelling electrodes because they can maintain electrical conductivity when strained. Although elastomers with microchannels are typically used to create soft devices by injecting liquid metal into the channels, the resulting topographic structures of ExSil 100 are prone to collapse owing to the ultrasoftness of the elastomer. The oxidized liquid metal, which showed excellent wetting behavior, was therefore patterned by forced wetting through stencils onto the substrate. The desirable properties of the elastomer have thus been synergistically harnessed with the “infinite stretchability” of the liquid metal to fabricate a variety of multifunctional electronic devices, illustrating successful utilization of this system in the field of soft and stretchable electronics.