A Monolithic Strain–Proximity–Pressure Trimodal Flexible Sensor for Healthcare Monitoring and Wearable Perception

Flexible electronic skins capable of multifunctional signal acquisition are indispensable for both personalized healthcare and immersive human–machine interfaces. However, integrating strain, proximity, and pressure sensing into a compact device is impeded by structural redundancy and performance trade-offs. Herein, we demonstrate an all-in-one trimodal sensor via an electrode-multiplexed architecture, where serpentine conductive traces function as both piezoresistive transduction and capacitive sensing. By leveraging the dual function of these shared electrodes, the system achieves a reduction in integration complexity. The serpentine-patterned electrodes are utilized to provide high strain sensitivity (gauge factor of 3.69, 0–20% range), while their complementary stacking maximizes the fringing effect for long-range proximity detection (0–100 mm). Moreover, the integration of a hierarchical iontronic interface effectively alleviates the sensitivity-range trade-off in pressure sensing (3.75 kPa^–1 at 0–60 and 0.99 kPa^–1 at 60–200 kPa). Consequently, the system demonstrates versatile utility in healthcare monitoring, which accurately captures radial artery pulses, muscle dynamics, and noncontact respiration patterns. Furthermore, the sensor enables physics-informed wearable perception by synergizing tactile and proprioceptive information, which successfully distinguishes material softness from structural compliance. This work provides a robust solution for versatile multimodal sensors and facilitates advanced applications in ubiquitous human–machine-environment monitoring and interaction.