Lubrication plays a vital role in flexible electronics and medical devices, yet achieving stable low friction under low-pressure hydrodynamic conditions remains challenging. Existing approaches often lead to a coefficient of friction (COF) that increases with sliding velocity, due to the instability of interfacial water layers. Inspired by ocular surface structures, we developed a bio-inspired lubricating hydrogel (BLH) with nanowire arrays that confine interfacial water. This confined water remains stable under pressure, allowing COF to stay low and nearly independent of velocity. Under eyelid pressure (1.3-7.0 kPa), BLH achieved an ultra-low COF (0.0079-0.028), representing a 34-80% reduction compared to flat hydrogels (FH) and approaching that of natural corneal surfaces (0.014-0.037). The low friction was sustained over prolonged durations (≈ 6,000 s) and maintained at blinking-relevant speeds (≈ 4 cm/s). Tests using pig-eyeball rubbing and endoscope-probe models further demonstrated the robustness of this strategy, highlighting its promise for low-hysteresis coatings, flexible electronics, and medical devices.

Gating, a fundamental feature of biological nanochannels, enables the intelligent regulation of ion and molecule transport in response to specific requirements. Inspired by nature, numerous artificial gating systems have been researched through the functionalization of solid-state nanochannels. However, these gating systems typically allow only two transitions: “open” and “closed”, which makes it challenging to achieve multi-state transport. Herein, we construct dynamic liquid film nanochannels (DLFNs) by inserting an oil droplet into a capillary with gradient wettability that is filled with ionic solutions. The liquid film, formed between the oil and the capillary, functions as a nanochannel for ion and molecule transport, with its height dynamically adjusted through the capillary's gradient wettability. At a deeper level, the variations in liquid film thickness are driven by the interfacial water structure, which is mediated by hydrogen bonding interactions. Furthermore, unlike traditional solid-state nanochannels, which involve two phases (liquid/solid), the properties of DLFNs are influenced by three phases (oil/water/solid), resulting in distinct performance characteristics, such as reconfigurability, low cost, and ease of fabrication. This work provides an avenue for designing dynamic nanofluids and may spark promising applications of DLFNs with multiscale gating properties in drug delivery, microreactors, sieving, biosensing, and other related fields.

90° is the limitation of lyophilicity and lyophobicity for ideal surface for centuries, but it has been proved to be contradictory on some occasions. The symmetrical surfaces with different surface tensions can attract or repel each other in water. Therefore, at the molecular level, the lyophilicity or lyophobicity is the results of interactions between the liquids and substrates. Here, using atomic force microscope (AFM) to measure interaction forces between symmetrical self-assembled monolayers (SAMs) in different liquids, we found that the SAMs repel each other when the surfaces are hydrophilic whereas attract when hydrophobic in water. The contact angle corresponding to the transition of attraction to repulsion is approximate to 65°, defined as the intrinsic wetting threshold (IWT) of water. For ethylene glycol (EG), dimethyl sulfoxide (DMSO), N,N-dimethyl formamide (DMF), the IWTs could be determined by changes of adhesion forces between SAMs. This research redefined the IWTs for liquids, which is the essential guide to both basic theory and applications of wettability.