Thermoresponsive Mobile Interfaces with Switchable Wettability, Optical Properties, and Penetrability

Solid-Liquid Host-Guest Composites: The Marriage of Porous Solids and Functional Liquids

Composite materials can provide remarkable improvements over the individual constituents. Especially, with a liquid component introduced into a solid porous host, solid-liquid host-guest composites have recently come to the forefront with exceptional functions that promise them for a wealth of applications. Combining the unprecedented dynamic, transparent, omniphobic, self-healing, diffusive and adaptive nature of functional liquid with inherent solid host's property, solid-liquid host-guest composites can realize the ease of fabrication, long-term stability, and a broad spectrum of enhanced properties, which cannot be fully met by conventional solid-solid composites or liquid-liquid composites. This review presents the state-of-the-art progress in solid-liquid host-guest composites. Initially, the concept, classification, design strategy, as well as fabrication methods as a path forward to develop the composites are unraveled, and further it is elaborated on how the functionality of porous solid and functional liquid can be harnessed to create composites with a broad range of unique properties, especially, the optical, thermal, electric, mechanical, sorption, and separation properties. With these fascinating properties, a myriad of emerging applications such as optical devices, thermal management, electromagnetic-interference shielding, soft electronics, gas capture and release, and multiphase separations are touched upon, inspiring more frontier researches in materials science, interfacial chemistry, membrane science, engineering, and multidisciplinary. Finally, this review provides the perspective on the future directions of solid-liquid host-guest composites and assesses the challenges and opportunities ahead.

Drops Sliding on Non-SLIPS Structures

Inspired by a plant leaf, a slippery liquid-infused porous surface (SLIPS) exhibits attractive nonwetting and self-cleaning abilities. However, rigorous requirements for the infused liquid layer and its inevitable loss limit its practical use. Here, we propose a model structure defined as a non-SLIPS by introducing solid nanostructures covered with a discontinuous lubricant film. This non-SLIPS tuned by solid wettability achieves the excellent self-cleaning feature with a small sliding angle comparable to the counterpart of a typical SLIPS. This sliding angle α* can be further reduced to a saturated plateau by a slight enhancement of hydrophobicity of the solid nanostructures. Interestingly, the sliding velocity remains almost constant for all of these non-SLIPS samples at a given tilt angle, independent of solid wettability. We formulate the slippery mechanism by defining an energy barrier responsible for the sliding initiation on the non-SLIPS. This energy barrier of the non-SLIPS is correlated, with a qualitative agreement, to the molecular adsorption on the solid nanostructures. The antibiological contamination is confirmed for this non-SLIPS, indicating its excellent self-cleaning ability. The findings suggest that the new surfaces, even with the gradual depletion of the infused oil layer, exhibit the nondegradation of the self-cleaning performance.

Liquid gating technology

Recent years have witnessed the emergence of liquid gating technologies that employ liquids as structural materials to provide dynamic gating control. Such technologies have attracted considerable attention globally owing their antifouling, energy-saving, reversible, and reconfigurable characteristics. This study considers a new perspective to discuss advancements in liquid gating technologies, including the concept, mechanisms, development, designs, and emerging applications. Moreover, recommendations are provided for the selection of the gating liquid and porous matrix, preparation processes, technical parameters, and theoretical modelling to guide related research. Emerging applications of liquid gating technologies, such as microscale flow control, multiphase separation, chemical detection, and biomedical catheters, are reported. Finally, the challenges currently faced by these technologies are discussed and potential directions for further research are explored to promote the use of these technologies in future applications.

Bioinspired liquid gating membrane-based catheter with anticoagulation and positionally drug release properties

Catheters are indispensable medical devices that are extensively used in daily medical treatment. However, existing catheter materials continue to encounter many problems, such as thrombosis, single functionality, and inadaptability to environmental changes. Inspired by blood vessels, we develop a self-adaptive liquid gating membrane-based catheter with anticoagulation and positionally drug release properties. Our multifunctional liquid gating membrane-based catheter significantly attenuates blood clot formation and can be used as a general catheter design strategy to offer various drugs positionally releasing applications to comprehensively enhance the safety, functionality, and performance of medical catheters' materials.

Liquid-based porous membranes

The confluence of available membrane materials and the explorations into fluid behaviors have revolutionized liquid-based porous membranes, which deserve more attention.

Bioinspired Slippery Lubricant-Infused Surfaces With External Stimuli Responsive Wettability: A Mini Review

Responsive slippery lubricant-infused surfaces (SLIS) have attracted substantial attention because of the high demand of fundamental research and practical applications, such as controllable liquid-repellency, intelligent, and easy-to-implement wettability switching. In this review, advanced development of responsive slippery surfaces is briefly summarized upon various external stimuli, including stress, electrical field, magnetic field, and temperature. In addition, remaining challenge and prospect are also discussed.

Deep Eutectic Solvent-Assisted In Situ Wood Delignification: A Promising Strategy To Enhance the Efficiency of Wood-Based Solar Steam Generation Devices

Wood-based solar steam generation devices (W-SSGDs) show great promise for desalination and wastewater treatment because they are inexpensive and sustainable. Technical methods for enhancing the efficiency of W-SSGDs have, so far, mainly focused on the optimization of solar-to-thermal conversion efficiency, whereas the properties of the wood matrix have been ignored. Here, we have designed a strategy using deep eutectic solvents to remove lignin from bulk wood in situ for the fabrication of a high-performance W-SSGD (DW-SSGD). Wood delignification increases the water transportation capacity while reducing thermal conductivity and conductive heat loss in the wood matrix. The improved properties of delignified wood allowed us to construct a high-performance DW-SSGD with a steam generation efficiency of 89% and an evaporation rate as high as 1.3 kg m^-2 h^-1 at 1 sun (100 mW cm^-2). To the best of our knowledge, the performance reported here is the highest for a W-SSGD under one solar irradiation.

Slippery Surface Based on Photoelectric Responsive Nanoporous Composites with Optimal Wettability Region for Droplets' Multifunctional Manipulation

The development of responsive slippery surfaces is important because of the high demand for such materials in the fields of liquid manipulation on biochips, microfluidics, microreactions, and liquid-harvesting devices. Although great progress has been achieved, the effect of substrate wettability on slippery surfaces stability is overlooked by scientists. In addition, current responsive slippery surfaces generally function utilizing single external stimuli just for imprecisely controlling liquid motion, while advanced intelligences are always expected to be integrated into one smart interface material for widespread multifunctional applications. Therefore, designing slippery surfaces that collaboratively respond to complex external stimuli and possess sophisticated composite function for expanding applications from controlling droplets motion to patterned writing is urgently needed but remains a challenge. Here, a photoelectric cooperative-responsive slippery surface based on ZnO nanoporous composites is demonstrated. First, the effect of composite surface wettability on slippery surface stability is systematically researched and the optimum wettability region for fabricating stable slippery surfaces is determined. Furthermore, controllable droplet motion and patterned writing are realized on the same slippery surfaces under photoelectric cooperative stimuli, and the related response mechanism is also deeply studied. This kind of material has potential applications in biochips, microfluidics, in situ patterning, and water-harvesting systems.

Self-Reporting Inhibitors: A Single Crystallization Process To Obtain Two Optically Pure Enantiomers

Collection of two optically pure enantiomers in a single crystallization process can significantly increase the chiral separation efficiency but this is difficult to realize. Now a self-reporting strategy is presented for visualizing the crystallization process by a dyed self-assembled inhibitor made from the copolymers with tri(ethylene glycol)-grafting polymethylsiloxane as the main chain and poly(N⁶ -methacryloyl-l-lysine) as side chains. When applied with seeds together for the fractional crystallization of conglomerates, the inhibitors can label the formation of the secondary crystals and guide the complete separation process of two enantiomers with colorless crystals as the first product and red crystals as the second. This method leads to high optical purity of d/l-Asn⋅H₂ O (99.9 % ee for d-crystals and 99.5 % for l-crystals) in a single crystallization process. It requires a small amount of additives and shows excellent recyclability.

Thermo-responsive recoverable polymeric inhibitors for the resolution of racemic amino acids

Novel polymeric inhibitors with lower critical solution temperatures in water were prepared and used to mediate the crystallization of racemic asparagine monohydrate, leading to chiral separation with 88.6 ee%. They could be recollected by simply elevating the temperature with a high yield of around 95% and reused without compromising the stereoselectivity and stability.

Temperature-Responsive Anisotropic Slippery Surface for Smart Control of the Droplet Motion

Development of stimulus-responsive anisotropic slippery surfaces is important because of the high demand for such materials in the field of liquid directional-driven systems. However, current studies in the field of slippery surfaces are mainly conducted to prepare isotropic slippery surfaces. Although we have developed electric-responsive anisotropic slippery surfaces that enable smart control of the droplet motion, there remain challenges for designing temperature-responsive anisotropic slippery surfaces to control the liquid droplet motion on the surface and in the tube. In this work, temperature-responsive anisotropic slippery surfaces have been prepared by using paraffin, a thermo-responsive phase-transition material, as a lubricating fluid and directional porous polystyrene (PS) films as the substrate. The smart regulation of the droplet motion of several liquids on this surface was accomplished by tuning the substrate temperature. The uniqueness of this surface lies in the use of an anisotropic structure and temperature-responsive lubricating fluids to achieve temperature-driven smart control of the anisotropic motion of the droplets. Furthermore, this surface was used to design temperature-driven anisotropic microreactors and to manipulate liquid transfer in tubes. This work advances the understanding of the principles underlying anisotropic slippery surfaces and provides a promising material for applications in the biochip and microreactor system.