Supramolecular Cross-Linking Enables Highly Stretchable and Ultrasensitive Polyurethane-Poly(3,4-ethylenedioxythiophene) Tactile Sensors

Wearable tactile sensors with high stretchability and stable electrical conductivity are crucial for next-generation applications in electronic skin, healthcare monitoring, and human-machine interaction. However, existing designs often encounter challenges related to the mechanical stiffening and signal nonlinearity caused by materials that lack both resilience and the ability of maintaining consistent electrical conductivity under deformation. Herein, we present a polyurethane-poly(3,4-ethylenedioxythiophene) (PU-PEDOT) tactile sensor cross-linked via supramolecular interactions to overcome these limitations. Although PEDOT incorporation provides essential electrical conductivity, its tendency to crystallize diminishes the tensile stretchability and compressive compliance of the PU matrix, undermining phase stability. To overcome this, we introduce a dynamic PolyFlex (PF) network PF-CDPEG, integrating PEGylated sliding cyclodextrins (pseudopolyrotaxanes) (CD-PR), poly(ethylene glycol) methacrylate (PEGMA), and poly(ethylene glycol) diacrylate (PEGDA). The α-CD rings threaded on PEG axles act as supramolecular zipper cross-links, dynamically dissociating and reassociating under strain to dissipate stress and preserve conductive pathways. The optimized PF-CDPEG-Opt sensor, with its engineered porous architecture and supramolecular cross-linking, achieved exceptional mechanical stretchability, sustaining strains up to 1550%, which is critical for next-generation wearable applications. The sensor also demonstrated rapid response and recovery (14 ms/12 ms) and high sensitivity (>300 kPa^-1), with a detection limit as low as 0.9-2 Pa. The sensor enables real-time monitoring of physiological signals, including arterial pulse, joint motion, and vocal cord vibration, under diverse conditions. These results demonstrated a scalable strategy for developing flexible and highly sensitive tactile sensors, with broad implications for soft robotics, artificial skin, and biomedical interfaces.