Geometry-engineered spring-shaped silicon nanowires for directional airflow sensing on flexible substrates

Precise detection of gentle airflow remains challenging for wearable sensors due to low flexibility and limited directional sensitivity in conventional nanowire designs. Inspired by mechanosensory hairs in human skin, we report a flexible, geometry-engineered airflow sensor based on suspended spring-shaped silicon nanowires (SiNWs), synthesized via an in-plane solid–liquid–solid strategy. The spring-shaped architecture is rationally designed to enhance axial compliance and mechanical resilience, significantly outperforming straight SiNWs under airflow-induced strain, as validated by finite element simulations and mechanical testing. The sensor demonstrates a rapid response time of 80 ms and a linear electrical output in response to gentle airflow ranging from 0.5 to 3 m/s under bending conditions. Notably, its unique structural anisotropy enables directional sensing at 0°, 45°, and 90°, with distinct current responses of 56%, 38%, and 16%, respectively. This work highlights geometry engineering as an effective strategy for enabling directional airflow detection in flexible nanowire-based systems.