Flexible TiO₂/GO hybrid films with laser-induced necking-enhanced micro/nano hierarchical structures for non-invasive wearable sweat lactate sensing

This work reports the fabrication of flexible TiO₂/graphene oxide (GO) hybrid ceramic films via nanosecond laser surface processing. The laser-induced micro/nano hierarchical ceramic structures are designed for non-invasive wearable biosensing applications. Laser modification at fluences ranging from 0.76 J/cm2 to 4.35 J/cm2 promoted interparticle fusion within the TiO₂ framework and partial reduction of GO, forming conductive bridges and stable oxide–carbon interfaces with necking-enhanced structures, where the necking ratio (N_r) reached 0.75. The laser-induced hierarchical texturing increased the surface roughness (R_a) from 92 nm (pristine) to 114 nm and concurrently reduced the surface contact angle (CA) from 95o to 28o, indicating enhanced hydrophilicity favorable for biofluid interaction. The laser-modified TiO₂/GO hybrid films further exhibited excellent mechanical durability, maintaining electrical stability with a relative resistance change (ΔR/R_o) below 5 % under 180o cyclic bending for 100 repetitions. Electrochemical characterization in lactate and artificial sweat environments demonstrated linear current responses over a concentration range of 2–10 mM with a sensitivity of 1 μA/mM and signal retention exceeding 95 % over 30 days. These results demonstrate a scalable laser-based strategy to engineer necking-driven ceramic hierarchical structures with tunable wettability and robust flexibility, enabling non-invasive wearable biosensing interfaces for sweat-based biochemical monitoring.