Mechanical decoupling on multiscale heterointerface for customizable and robust strain sensors

Strain sensors are pivotal for monitoring mechanical deformation across various fields, including robotics, prosthetics and wearable electronics. Crack-based strain sensors are favored among the diverse approaches for their high sensitivity. However, they face significant challenges, such as uncontrollable cracks and interface delamination between functional materials and flexible substrates. Here, we introduce a mechanical decoupling strategy using aluminum-3DLithography (AL-3DLitho), which enables out-of-plane mechanical anchoring and in-plane stress redistribution at the multiscale heterointerface. The introduced out-of-plane anchoring improves the adhesion of functional layers to polymer substrates, preserving electrical integrity even under harsh conditions such as ultrasonic exposure. Additionally, the controlled in-plane strain localization and the enhanced stress intensity factor allow precise adjusting of crack propagation modes and densities, enabling customization of sensing performance. The resulting strain sensor, featuring optimized nanofiber and micropyramid arrays at the multiscale heterointerface, achieves a gauge factor exceeding 100,000 with customizable working ranges from 0.005% to 75% and minimal signal drift (<1%). This ultrasensitive sensor, capable of detecting surface topography with a height resolution of 2.7 μm through indirect contact, offers promising applications in flexible electronics where tactile feedback is critical.