Bio-inspired Air-Shield Strategy Enables Zero-Contact Repellency

Minimizing interfacial liquid-solid contact is central to self-cleaning and protective fabrics, yet passive microtextures generally permit transient contact during impact. Here, we demonstrate a bio-inspired airflow-mediated strategy that converts superhydrophobic fabrics from passive low-adhesion surfaces into pressure-programmable active repellent interfaces. This strategy is implemented by covalently anchoring continuous nanoscale superhydrophobic shells onto the microscale fibers, which maintains a low-adhesion interfacial Cassie-type wetting state at the nanoscale even after 20,000 abrasion cycles, 15,300 scrub resistance cycles, and 3000 bending cycles, and delivering airflow through interconnected fabric pores to supply a replenishable interfacial counter-pressure required for levitating and redirecting impacting droplets of 2-20 μL (equivalent spherical diameters ≈ 1.6-3.4 mm). A pressure-controlled sequence is resolved from contact rebound to suspended rebound and finally to an operational zero-contact rebound, defined as no liquid-solid contact. Compared with conventional optical imaging, synchrotron X-ray imaging at 10,000 frames s-1 with 2 μm spatial resolution enhanced the detection resolution. Nanostructure-reinforced surface superhydrophobicity reduces interfacial adhesion and pore-invasion risks and provides fail-safe repellency below the zero-contact airflow threshold. The threshold pressure for zero-contact rebound is found as a scaling correlation in terms of droplet impact velocity and fabric pore size. The coupled droplet-gas-film-fabric model separates liquid inertial-deformation demand from gas-flow loss in the fabric, with a globally calibrated two-coefficient linear-quadratic relation describing the measured velocity-pressure pairs. The proof-of-concept demonstrations on breathable masks, tents, and garments illustrate how these nanostructure-enhanced superhydrophobic fabrics can assist in spray and fog protection and modulate surface temperature and local infrared temperature contrast.