Dynamic liquid film nanochannels for adjustable ion and molecule transport

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.