Highly Stretchable Polyrotaxane Thin-Film Substrates for Printed Electronics

Thin polymeric films with high mechanical robustness and stretchability are essential for the development of flexible and stretchable electronic devices. Here, we present a versatile strategy for fabricating freestanding polymer films with tunable mechanical properties while maintaining large stretchability. The films are fabricated by chemically cross-linking multi-arm poly(ethylene glycol) acrylate (4-arm-PEG-A) with polyrotaxane (PR) units composed of α-cyclodextrins (α-CDs) threaded along a linear PEG backbone. By varying the degree of PR functionalization and its content, the mechanical properties of the films can be systematically tuned, enabling simultaneous enhancement of strength, toughness, and stiffness, with failure strains exceeding 150%. The resulting films were used as substrates for stretchable temperature sensors, which maintained stable performance under an applied strain of ~60%. These results demonstrate that polyrotaxane-based thin films provide mechanically robust and functionally compatible substrates for stretchable electronics operating under large deformations.