Strain-Insensitive Iontronic Tactile Sensor with Rigid-Soft Hybrid Architecture for Cardiovascular Assessment

Mechanical deformation of human skin often induces strain-pressure crosstalk and compromises signal reliability. Here, we present a strain-insensitive iontronic tactile sensor by introducing a rigid-soft hybrid architecture to decouple pressure signals from tensile strain. Rigid microspheres are embedded into a stretchable iontronic film to construct an iontronic interface with a soft conductive electrode. The iontronic interface exhibits a strain-independent contact area under uniaxial strain up to 50%, as confirmed by finite element simulations and experimental results. This design enables consistent capacitive responses under stretching and bending states, ensuring high-fidelity pressure sensing under dynamic skin motion. Integrated with a robotic arm, the tactile sensor captures high-fidelity pulse waveforms from multiple arterial sites and distinguishes between healthy, hypertensive, and coronary heart disease subjects through second-derivative waveform analysis. This strain-decoupling strategy establishes a universal approach for strain-insensitive tactile sensing, enabling practical applications in biomedical monitoring and future adaptive electronic systems.