Supermetalphobic surfaces fabricated by femtosecond laser enable reliable and low-hysteresis liquid metal based flexible capacitive pressure sensor

Room-temperature Ga-based liquid metal (LM) alloys, as soft conductive materials with high liquid mobility, offer an excellent alternative for the fabrication of flexible electronics, especially in the field of flexible sensors. However, LM are highly susceptible to oxidation. The formation of an oxidized layer on the surface of LM with high adhesion will hinder continuous contact between the electrode and the dielectric layer, thus seriously affecting the stability and resulting in elevated hysteresis of sensors. Herein, a supermetalphobic dielectric layer is fabricated by femtosecond laser for an LM-based high-performance capacitive pressure sensor. Femtosecond laser-fabricated micro-nano hierarchical structures with supermetalphobicity are able to reduce the adhesion dramatically between the LM oxide layer and the dielectric layer of the sensors so that no adhesion-related damage occurs. The performance of the sensors with different dielectric layer structures has been compared by simulation and experiment. The results demonstrate that the sensor based on supermetalphobic surface exhibits significant advantages over other structures in terms of high sensitivity (1.14 kPa⁻¹), excellent pressure-response stability, and low hysteresis (3.56 %). Additionally, it demonstrates a limit of detection (∼0.9 Pa), and rapid response and recovery time (∼50 ms). Moreover, the all-soft pressure sensor array was fabricated based on the micro-nano manufacturing of femtosecond laser achieving a high signal-to-noise ratio and object recognition capability.