Multifunctional Conductive Hydrogel/Thermochromic Elastomer Hybrid Fibers with a Core–Shell Segmental Configuration for Wearable Strain and Temperature Sensors

Flexible wearable sensors are emerging as next-generation tools to collect information from the human body and surroundings in a smart, friendly, and real-time manner. A new class of such sensors with various functionality and amenability for the human body is essential for this goal. Unfortunately, the majority of the wearable sensors reported so far in the literature were of a single function (mostly strain sensors) and just a prototype without thinking of continuous mass production. In this paper, we report a series of multifunctional conductive hydrogel/ thermochromic elastomer hybrid fibers with core-shell segmental configuration and their application as flexible wearable strain and temperature sensors to monitor human motion and body/surrounding temperatures. Specifically, a conductive reduced-graphene-oxide-doped poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylamide (rGO-poly(AMPS-co-AAm)) hydrogel and a thermochromic elastomer containing silicon rubber and thermochromic microcapsules are chosen as strain-sensitive and thermosensitive materials, respectively. A core-shell segmental structure is realized by programming the extrusion of either conductive hydrogel precursor solution or a thermochromic elastomer prepolymer as a core layer via dual-core coaxial wet spinning. Depending on the assembly order and length of the conductive hydrogel and the thermochromic elastomer, the as-prepared hybrid fibers can be used for different purposes, i.e., human-motion monitoring, body or room temperature detection, and color decoration. The strategy described above, i.e., fabrication of core-shell segmental fibers via the wet-spinning method, is especially suitable for mass production in industry and can be further extended to fabricate flexible wearable devices with more components and more functions such as transistors, sensors, displays, and batteries.