Search

Studying nature to reveal the mechanisms of special wetting phenomena in biological systems can effectively inspire the design and fabrication of functional interfacial materials with superwettability. In this Review, the historical development, new phenomena and emerging applications of superwettability systems are discussed.

Placing particles at the interface between immiscible fluids usually enhances emulsification. However, now it is shown that if the particles are ferromagnetic, emulsification is suppressed and a non-planar recoverable interfacial shape develops.

Oil repellency using polyfluoroalkyl substances are broadly applicable, though unfavorable due to high fluorine composition. Here the authors report a polydimethylsiloxane-based system using single CF₃ groups affording oil repellency with low fluorine composition.

The welding and sintering of nanoparticles is relevant, for example, to establish electrical contacts between particles in printed electronic devices. Here, using electron microscopy and computer simulations, Grouchko et al. discover a room-temperature sintering process driven by a selective wettability of silver nanoparticles independent of their shape.

The characterisation of interfacial layers, whose rheology can differ from the bulk, is important for the design of new materials. Here, Lhermerout et al. use the dynamics of a moving contact line to quantify the mechanical properties of a polymer thin film.

Elastic deformation of soft substrates occurs upon wetting, yet it is challenging to follow its dynamics at a microscale. Khattak et al. show that the force required to pull a droplet along a soft surface decreases monotonically as the film thickness decreases and explain the phenomenon using a scaling analysis.

It is known that liquid drops can be levitated by continuous vapour flow above a liquid surface. Here the authors combine the ultra-low friction provided by the bath with the interaction force between two drops due to interface deformations to study the dynamics of interactions between multiple objects.

Hydrophobic surfaces composed of an asymmetric array of polymer nanorods show unidirectional wetting behaviour relative to the orientation of the tilted nanorods. The surfaces, which are smooth on the microscale, can transport water droplets of microlitre capacity by a ratcheting mechanism resulting from the pillared substrate.

Lubricated surfaces are known to display extreme liquid repellency. Such behaviour is now confirmed to be due to the formation of a film between the surface and the repelled liquid, with a thickness profile following the Landau–Levich–Derjaguin law.

Droplet evaporation control has applications in inkjet printing and surface patterning. Here, the authors show that on slippery curved substrates droplets evaporate by slowly retracting and then suddenly snapping, which can be exploited to design surfaces that control an evaporation sequence.

Design of rewritable wettability pattern of low surface tension liquids is a challenging task to achieve. Here, authors introduced a chemically reactive crystalline network of polymer to develop rewritable and liquid-specific wettability pattern via spatially selective chemical modification.

Techniques to alter the surface of materials to enable transport of fluids have advanced considerably, but dynamic microdroplet transport remains a challenge. Here, the authors report the fabrication of microtextured chemical gradients on elastomer films and their use in controlled microdroplet transport.

Stable coating of filters with a thin liquid layer enhances adhesion of airborne particulates while maintaining high air permeability, resulting in longer lifetimes and higher efficiency of these filters.

Controlling the movement of floating objects at small scales is essential for microfluidics, but traditional methods are limited by fluid and object properties. By shaping liquid interfaces with 3D-printed spines, the study enables programmable manipulation of floating particles for applications like sorting and cleaning.

Slippery covalently attached liquid surfaces are useful in many applications that require low-static friction to droplets. This review compares six prominent methods for preparing polydimethylsiloxane bound to silica surfaces and highlights pitfalls and time savers.

This study develops a liquid-gating topological gradient microfluidics device that generates finely tuned microbubbles in a functional liquid in a high-throughput manner for air purification in different scenarios.

Efficient small-scale fluid capture and transport is essential for point-of-care diagnostics but faces trade-offs between speed, volume, and flow resistance. Inspired by hummingbirds, the proposed elastocapillary device enables rapid, passive fluid capture and aliquoting, combining capillarity and elasticity for optimal performance.

The study of wave propagation at interfaces in various conditions, including deep and shallow water, has garnered significant interest over centuries. This work explores a class of capillary waves traveling on the plastron of underwater superhydrophobic surfaces, hence the name “plastronic waves”, with extraordinary fast propagation speed and applications for monitoring microscale gas layer stability.

Solid-state pressure sensors have performance limitations in liquid environments. Here, the authors design a pressure sensor using solid–liquid–liquid–gas multiphasic interfaces where a trapped air layer modulates capacitance changes with pressure to achieve near-friction-free contact line motions for near-ideal pressure sensing.

Shape-changing materials have potential in a range of applications, but these transformations can be challenging to control. Here, the authors report the hydrophobic pseudo-hydrogel, which utilizes absorption-induced expansion via elastocapillarity to enable versatile soft robotic applications.

Asymmetric mechanical transducers are pivotal in various applications; however, conventional methods demand continuous energy and intricate fabrication. Here, the authors demonstrate a droplet-based mechanical transducer utilizing wettability-patterned surfaces, enabling precise control of droplet dynamics.

Systems comprising water and hydrophobic cavities, with scales ranging from nanometres to millimetres, are shown to expand upon compression, an unusual mechanical property of technological and biological relevance known as negative compressibility.

Rewritable surface charge density gradients enable the direct, high-speed and long-distance transport of droplets on distinct surfaces without the need of additional energy input.

Water drops placed at rest on flat, hot solids are found to rotate and spontaneously propel themselves in the direction of their rotation. The effect is due to symmetry breaking of the flow inside the drop, which couples rotation to translation.

Tissue adhesives have received significant interest for their clinical utility but are typically incompatible with advanced manufacturing methods. Here, the authors introduce a 3D printable tissue adhesive for the fabrication of patches and devices for diverse biomedical applications.

Approaches for controlling surface wettability and liquid spreading are numerous and diverse, but introducing directionality to the control of these phenomena is far from trivial. Nanostructured surfaces are now used to allow the propagation of a liquid in a single direction, while constraining it in the other three directions.

Micrometre-sized particles covered with stiff, nanoscale spikes are shown to exhibit long-term colloidal stability in both hydrophilic and hydrophobic media, without the need for chemical coating, owing to the effect of the spikes on the contact area and, consequently, the force between the particles.

Many plants and animals make use of biological surfaces with structural features at the micro- and nanometre-scale that control the interaction with water. The appearance of dew drops on spider webs is an illustration of how they are one such material capable of efficiently collecting water from air. The water-collecting ability of the capture silk of the Uloborus walckenaerius spider is now shown to be the result of a unique fibre structure that forms after wetting.

Highly bendable yet unstretchable ultrathin sheets can wrap a liquid droplet to form an optimal non-spherical shape that minimizes the unwrapped interfacial area, regardless of interfacial energies and the sheet’s mechanical properties.

The controlled formation of micrometre-size drops is of importance for many technological applications such as microfluidics. A wetting-based destabilization mechanism of forced microfilaments on either hydrophilic or hydrophobic stripes leading to the periodic emission of droplets can now be used to control independently the drop size and emission period.

When a water drop bounces back from a hydrophobic surface, its initial, spherical shape is usually restored. Now, experiments with a specially engineered superhydrophobic surface made from micrometre-sized tapered pillars covered with copper oxide ‘nanoflowers’ show that droplets can bounce back with a flat, pancake-like shape.

Developing efficient separation methods for oily wastewater holds significant global importance. In this study, the authors combine supewettability and bio-inspired topological structures to demonstrate a dual-bionic superwetting gear system with liquid directional steering to achieve oil-water separation.

Liquid metals that have enormous surface tension are difficult to pattern into films. Here, authors report the spontaneous and selective wetting of a gallium-based liquid metal, which is induced by imbibition on a micro-structured metallized substrate.

Anisotropic functional patterned surfaces have shown significant applications in microfluidics, biomedicine, and optoelectronics. Here, authors demonstrate a fast and mask-free etching method for accurate surface patterning by confined decomposition, enabling the efficient fabrication of complex patterns.

A uniform particle deposition is crucial for sensitive applications, such as sensors and electronics. Here, authors introduce a passive protocol to suppress the coffee-ring effect and form uniform films at micro- and nanoscales combining superhydrophilic substrate with a neutral-wetting low-roughness mold.

Wang et al. report an underwater capillary adhesive that is strengthened by the conjunction of inner water bridge and outer air shell, and switched timely by a small direct current voltage. The design can also be constructed on flexible tapes, which can be applied to non-conductive substrates.

Ferrofluids with their extreme deformability are being used as soft machines. Using ferrofluids, Sun et al. show a variety of soft machines by playing with the wetting properties of solid surfaces

The momentum transport dynamics of a vaporizing droplet under low pressures remain undiscovered. Here authors report the vaporization momentum resulting from the intensive vaporization on the free surface of the water droplet contributes to the self-detachment of freezing droplets.

Janus membranes are highly valued for their unique water unidirectional transportation capabilities. Here, authors report an on-demand mode-switching strategy that significantly enhances the durability of the Janus membrane.

Currently, the anti-icing performance limitation of superhydrophobic materials is gradually approached without the assistance of an external field. Here, the authors propose a strategy of microdroplet movement manipulation induced by interfacial airflow for further improving the anti-icing performance.

A flexible hemline-shaped microfiber featuring periodic parallel microcavities with sharp edges and wedges was developed using microfluidics to achieve unidirectional liquid transport along arbitrary pathways.

Despite promising for anti-icing applications, structured superhydrophobic surfaces usually lose their hydrophobicity after a few icing/melting cycles. Here, authors investigate specific structured surfaces and air bubbles on frozen ice droplets to propose three criteria to enable dewetting transitions.

In classical wetting, the spreading of a drop on a surface is preceded by a bridge directly connecting the drop and the surface, yet it ignores the solubility of the drop phase in the medium. Here, the authors show that dissolved drop fluid from the parent drop can nucleate on the surface as islands, one of which coalesces with the parent drop to effect wetting.