Crack-Interlocked Metal/Elastomer Interfaces for Preload-Adapted Backside Pressure Sensing.

Flexible pressure sensors capable of resolving small pressure variations under large static loads are desirable for embedded and backside-mounted monitoring, where the sensing layer cannot be directly exposed to the contact surface. However, most highly sensitive pressure sensors are optimized for low-pressure operation, and their sensitivity decreases under preloads. Here, we report a crack-interlocked ridge structure composed of two facing PDMS micro-ridge arrays and a thin Pt conductive layer. The interlocked architecture converts vertical compression into localized tensile deformation at the Pt/elastomer interface, producing a reproducible crack-mediated resistance transition near a designed preload. The resulting sensor exhibits a maximum local sensitivity of 2582.8 kPa-1 within the transition window and maintains repeatable responses over 1000 loading-unloading cycles. By varying the interlayer thickness, the active sensing window can be shifted across 50-700 kPa, enabling preload-adapted pressure-change detection in mechanically biased configurations. As a proof of concept, the sensor detects a small additional load placed on a heavy object in a backside-mounted configuration. This crack-interlocked interface design provides a strategy for mechanically programming the pressure window of flexible resistive sensors for embedded monitoring applications.