Laser-Induced Irregular Hierarchical Interface Structures Offering High Sensitivity and Broad Detection Range of Flexible Pressure Sensors.

Abstract

Flexible pressure sensors have emerged as key enablers for wearable electronics and human-machine interfaces. Currently, introducing microstructures into the sensing medium is commonly adopted to tailor sensor performance. However, conventional single-scale structures (purely nano‑ or micro-scale) struggle to balance high sensitivity with a broad sensing range, and the corresponding fabrication processes are generally complex, time‑consuming, and incompatible with large-scale production. This study proposes a hierarchical architecture endowed with the synergistic effect of micro/nanostructures and develops a hybrid manufacturing strategy combining femtosecond laser processing and precision molding to enable high-quality, low-cost, scalable fabrication of such structures on pressure-sensing substrates. Specifically, femtosecond laser is employed to create the micro/nanoscale hierarchical structures on titanium alloy templates, which then act as durable molds to realize mass replication of flexible pressure‑sensing substrates. Within this dual-scale framework, nanoscale features are designed to achieve high sensitivity detection in the low‑pressure region, while the relatively large structures (microscale) help extend the overall sensing range. Benefiting from the synergistic effect of such multilevel micro/nanostructures, the as‑fabricated sensor exhibited a broad pressure detection range of 0.014-420 kPa with a stable response and achieved a high sensitivity of 0.87423 kPa-1 within the 0-2.3 kPa interval. Moreover, the device demonstrated a rapid response time of 40 ms and a recovery time of 60 ms and maintained consistent sensing performance after a 3-week long-term durability test consisting for 20,000 loading-unloading cycles. Practical test verifies that sensors with hierarchical micro/nanostructures enable accurate and reliable detection of the full spectrum of signals generated by human daily living and various activities, ranging from subtle human physiological signals (e.g., voice and pulse waveforms), moderate motion signals (e.g., joint flexion and limb movement), to large dynamic load motions (e.g., walking). The well-balanced overall performance makes the sensor highly promising for wearable health monitoring and human-machine interaction. Furthermore, this work offers an innovative manufacturing route for the design and mass production of next-generation high-performance flexible pressure sensors.