Bioinspired Flexible Tactile Sensor with Hierarchical Concave Microstructures for Wide-Range Biophysical Signal Monitoring and Pulse Mapping.

Flexible capacitive tactile sensors for human biophysical signal monitoring require the simultaneous realization of high sensitivity and a wide detection range, which remains challenging due to the intrinsic structural characteristics of the dielectric layer. Addressing this challenge requires new structural strategies that integrate compliant deformation with mechanical robustness. Here, we present a bioinspired flexible tactile sensor featuring a hierarchical concave microstructure derived from octopus suckers, fabricated via a facile and scalable template-transfer approach that enables precise structural replication and tunable sensing characteristics. Finite element simulations and mechanical characterization were employed to elucidate the pressure-dependent deformation behavior. The results reveal a graded deformation mechanism, where the peripheral rim and central protrusion engage sequentially to delay structural saturation and redistribute stress. As a result, the sensor exhibits segmental sensitivity and high linearity across a wide range of pressures, achieving 8.78 kPa-1 (0-5 kPa), 1.84 kPa-1 (5-230 kPa), and 0.91 kPa-1 (230-500 kPa), with corresponding linearities of 99.34, 97.83, and 98.98%, respectively. Furthermore, the device enables multimodal detection of biophysical signals and spatiotemporal reconstruction of pulse waves, advancing their application in noninvasive medical systems.