Bio-based polyurethanes for flexible wearable mechanical sensors: synthesis, functional design and applications

Abstract

The rapid growth of wearable electronics has increased the demand for soft, skin conformal and durable mechanical sensors that can record subtle physiological and motion related signals. Bio-based polyurethanes (BPUs), prepared from renewable polyols and non-isocyanate routes, are drawing attention as sustainable alternatives to petroleum-derived counterparts because their segmental structures are tunable and they offer a useful balance of flexibility and environmental compatibility. This review summarizes recent progress in the synthesis and functional design of BPU systems, including polyols derived from plant oils, lignin and sugars, as well as non-isocyanate networks obtained through cyclic carbonate and dimethyl carbonate (DMC) chemistry. It discusses key functional features such as adhesion, self-healing, shape-memory behavior, recyclability and antibacterial activity in relation to their chemical origins and structure property relationships. The use of these materials in piezoresistive, piezoelectric, triboelectric and capacitive sensors is also outlined, with examples that demonstrate advances in sensitivity, stretchability, stability and self-powered operation. Remaining challenges include lowering synthesis cost, improving long-term reliability and achieving effective multifunctional integration. With closer coupling between polymer chemistry and flexible electronics, BPUs are likely to play an important role in future wearable sensing technologies.