A Strain Decoupling Packaging Strategy for High-Fidelity Ultrathin Silicon Shape Sensors for Soft Medical Robotics

Reliable soft sensors are essential for precise control, real-time feedback, and safe operation in soft medical robots. Ultrathin silicon piezoresistive sensors offer flexibility, durability, and high sensitivity, but protecting them from external stress while maintaining softness remains challenging. Existing packaging strategies often compromise flexibility and induce excessive strain, leading to device failure. Here, we introduce an oil-lubricated slidable packaging approach that enables high-fidelity shape sensing of ultrathin silicon gauges by mechanically isolating the sensing element within a dual-layer film. This design decouples the sensor from the packaging, minimizing bending strain on the sensing element. Experimental results show that the sensor maintains stable and reliable signals under large applied strains, with fast response (<0.40 s), low hysteresis (∼3 %), and durability over more than 10 000 bending cycles at a 2 mm radius. The sensor was successfully integrated into a flexible endoscope, enabling precise shape detection under continuous 360° unidirectional bending, demonstrating feasibility for complex 3D perception. This work addresses long-standing packaging challenges in ultrathin flexible devices and provides a structurally protective strategy for reliable shape sensing in flexible electronic systems.