Natural deep eutectic solvents as plasticizers for advancing sustainable strain sensors.

Sustainability is driving the replacement of fossil fuel-derived materials with renewable alternatives. Transient electronics designed for short-term wear, such as resistive sensors, are poised to benefit from such initiatives by improving their environmental footprint. Their fabrication principally from renewable constituents with established degradability would increase their environmental circularity and eliminate their accumulation as electronic waste owing to their eventual degradation. This raises an important question: which ecologically benign materials can be integrated into resistive sensors for improving the circularity of such transient electronics without sacrificing sought-after metrics such as gauge factor sensitivity, stretchability, softness, and mechanical robustness? Combined soft and stretchable substrates fabricated from sustainable and degradable components, including chitosan and natural deep eutectic solvents (NADESs), were evaluated for use as wearable transient resistive sensors to resolve this question. The best composition of the stretchable self-standing films with NADESs fabricated with different carboxylic acids for resistive sensors was assessed. Mechanical testing revealed that the substrates plasticized exclusively with NADESs from malonic and lactic acids with choline chloride sustained elongations of