Stretchable, adhesive, conductive hydrogel initiated by liquid metal complex for multi-functional sensing

Liquid metal (LM) can serve as functional fillers, initiators, and cross-linkers for hydrogels. However, the high surface energy of LM makes it difficult to disperse uniformly and stably in the hydrogels. In this work, multi-walled carbon nanotubes (MWCNT-80) modified with the surfactant Tween 80, along with hyaluronic acid (HA), were employed to collectively stabilize LM to form LM complex for initiating the polymerization of vinyl monomers. The LM complex was used as a conductive filler, which not only enhanced the mechanical properties of the hydrogel, but also initiated free radical polymerization of the monomer. The prepared liquid metal conductive hydrogel (LMCH) has excellent stretchability (1192 %), adhesion (15.3 kPa) and conductivity (0.78 S/m). This LMCH hydrogel was further applied in the construction of multifunctional sensors. On one hand, strain sensors constructed with this hydrogel could monitor extensive joint range movements in real-time. On the other hand, a flexible triboelectric nanogenerator (L-TENG) constructed with the hydrogel as an electrode was employed for self-powered sensing. When integrated with a Microcontroller Unit (MCU), the joint training status of individuals can be transmitted in real-time to a mobile phone, allowing for the quantification and monitoring of human activities. This study presents a novel approach to the development of hydrogels for multifunctional sensors, and the prepared hydrogel holds significant potential in the fields of rehabilitation training and human–machine interaction.