Light-induced manipulation of ultra-low surface tension droplets on stable quasi-liquid surfaces.

HYPOTHESIS: Perfluorocarbon is commonly used as a coolant, chemical reaction carrier solvent, medical anti-hypoxic agents and blood substitutes. The realization of non-contact complex manipulation of perfluorocarbon liquids is urgently needed in human life and industrial production. However, most liquid-repellent interfaces are ineffective for the transport of ultra-low surface tension perfluorocarbon liquids, and struggle to maintain good durability due to unstable air or oil cushions in the surface. Therefore, preparing surfaces for stable non-contact complex manipulation of ultra-low surface tension droplets remains a challenge. EXPERIMENTS: In this paper, a novel solution, a photothermal responsive droplet manipulation surface based on polydimethylsiloxane brushes, has been reported. On this surface, droplets with different surface tensions (as low as 10 mN/m) can be efficiently manipulated through induced near-infrared light. Notably, this surface maintains its effectiveness after exposure to extreme anthropogenic conditions. FINDINGS: The interface effect between perfluorocarbon droplets and polydimethylsiloxane brushes by near-infrared light-induced was investigated in detail. In addition, ultra-low surface tension droplets demonstrate the ability to transport solid particles. The conductive droplets exhibit sophisticated manipulation realizing the controlled switching of smart circuits. This research opens up new possibilities for advancing the capabilities and adaptability of ultralow surface tension droplets in a range of applications.

An Active Strategy Based on Different Droplet Removal Modes on Polydimethylsiloxane Magnetic Microstructures.

The efficient removal of droplets on solid surfaces holds significant importance in the field of fog collection, condensation heat transfer, and so on. However, on current typical surfaces, droplets are characterized by a passive and single removal mode, contingent on the traction force (e.g., capillary force, Laplace pressure, etc.) generated by the surface's physics and chemistry design, posing challenges for enhancing the efficiency of droplet removal. In this paper, an effective active strategy based on different removal modes is demonstrated on magnetic responsive polydimethylsiloxane (PDMS) superhydrophobic microplates (RM-MPSM). By regulating the parameters of microplates and droplet volume, different effective departure modes (top jumping and side departure) can be induced to facilitate the removal of droplets. Moreover, the removal volume of droplets through the side departure mode exhibits a significant reduction compared to that observed in the top jumping mode. The exceptional removal ability of RM-MPSM demonstrates adaptability to diverse functional applications: efficient fog collection, removal of condensation droplets and micro-particles. The efficient modes of droplet removal demonstrated in this work hold significant implications for broadening its application in many fields, such as droplet collection, heat transfer, and anti-icing.

Enhanced and controlled droplet ejection on magnetic responsive polydimethylsiloxane microarrays.

Efficient removal of droplets from solid surfaces is significant in various fields, including fog collection and condensation heat transfer. However, droplets removal on common surfaces with static structures often occurs passively, which limits the possibility of increasing removal efficiency and lacks intelligent controllability. In this paper, an active strategy based on extrusion ejection is proposed and demonstrated on the magnetic responsive polydimethylsiloxane (PDMS) superhydrophobic microplates (MPSM). The MPSM can reversibly transit between the upright and tilted state as the external magnetic field is alternately applied and removed. Under the magnetic field, the direction and trajectories of droplets departure can be intelligently controlled, demonstrating excellent controllability. More importantly, compared with the static structure where the droplet must reach a certain size before departure, droplets can be ejected at smaller sizes as the MPSM is tilted. These advantages are of great significance in many fields, such as a highly efficient fog harvesting system. This strategy of extrusion ejection based on dynamic surface structure control reported in this work may provide fresh ideas for efficient droplet manipulation.

Triple-Bioinspired Shape Memory Microcavities with Strong and Switchable Adhesion.

Smart adhesives with switchable adhesion have attracted considerable attention for their potential applications in sensors, soft grippers, and robots. In particular, surfaces with controlled adhesion to both solids and liquids have received more attention, because of their wider range of applications. However, surfaces that exhibit controllable adhesion to both solids and liquids often cannot provide sufficient adhesion strength for strong solid adhesion. To overcome this limitation, this study developed a triple-bioinspired shape memory smart adhesive, drawing inspiration from the adhesion structures found in octopus suckers, lotus leaves, and creepers. Our adhesive design incorporates microcavities formed by a shape memory polymer (SMP), which can transition between rubbery and glassy states in response to temperature changes. By leveraging the shape memory effect and the rubber-glass (R-G) phase transition of the SMP, the adhesion of the surface to smooth solids, rough solids, and water droplets could be switched by adjusting the temperature and applied force. Notably, the adhesives designed herein exhibited high adhesion strength (up to 420 kPa) on solids, facilitated by the shape interlocking effect and the negative pressure generated within the microcavities. Furthermore, the programmable transport of solids and liquids can be achieved by utilizing this switchable adhesion. This approach expands the possibilities for designing smart adhesives and holds potential for various applications in different fields.

Biodegradable electrospinning superhydrophilic nanofiber membranes for ultrafast oil-water separation.

Although membrane technology has attracted considerable attention for oily wastewater treatment, the plastic waste generated from discarded membranes presents an immediate challenge for achieving eco-friendly separation. We designed on-demand biodegradable superhydrophilic membranes composed of polylactic acid nanofibers in conjunction with polyethylene oxide hydrogels using electrospinning technology for ultrafast purification of oily water. Our results showed that the use of the polyethylene oxide hydrogels increased the number of hydrogen bonds formed between the membrane surface and water molecules by 357.6%. This converted hydrophobic membranes into superhydrophilic ones, which prevented membrane fouling and accelerated emulsion penetration through the membranes. The oil-in-water emulsion permeance of our newly designed nanofiber membranes increased by 61.9 times (2.1 × 104 liters per square meter per hour per bar) with separation efficiency >99.6%, which was superior to state-of-the-art membranes. Moreover, the formation of hydrogen bonds was found to accelerate polylactic acid biodegradation into lactic acid by over 30%, offering a promising approach for waste membrane treatment.

Surface manipulation for prevention of migratory viscous crude oil fouling in superhydrophilic membranes.

Here, we present a proactive fouling prevention mechanism that endows superhydrophilic membranes with antifouling capability against migratory viscous crude oil fouling. By simulating the hierarchical architecture/chemical composition of a dahlia leaf, a membrane surface is decorated with wrinkled-pattern microparticles, exhibiting a unique proactive fouling prevention mechanism based on a synergistic hydration layer/steric hindrance. The density functional theory and physicochemical characterizations demonstrate that the main chains of the microparticles are bent towards Fe3+ through coordination interactions to create nanoscale wrinkled patterns on smooth microparticle surfaces. Nanoscale wrinkled patterns reduce the surface roughness and increase the contact area between the membrane surface and water molecules, expanding the steric hindrance between the oil molecules and membrane surface. Molecular dynamic simulations reveal that the water-molecule densities and strengths of the hydrogen bonds are higher near the resultant membrane surface. With this concept, we can successfully inhibit the initial adhesion, migration, and deposition of oil, regardless of the viscosity, on the membrane surface and achieve migratory viscous crude oil antifouling. This research on the PFP mechanism opens pathways to realize superwettable materials for diverse applications in fields related to the environment, energy, health, and beyond.

Narrow response temperature range with excellent reversible shape memory effect for semi-crystalline networks as soft actuators.

Complex and controlled reversible actuation inevitably relies on changing thermal fields (direct or indirect) for semi-crystalline reversible shape memory networks. Unfortunately, the non-tunability of thermal signals often brings potential limitations to actuators' applications. In practice, a wide response temperature range (T-range) formed by Thigh and Tlow in the remarkable reversible actuation is an obvious fact. Herein, we demonstrate the tunability of the transition temperatures while stably maintaining excellent actuation abilities. We further verified that the narrow T-range (24 °C) that had not been reported could present more than 17% reversible strain. Special parameter optimization provides opportunities for potential non-implantable biomedical applications. Therefore, based on target 2W-SMP, a vehicle concept with the drug release and vehicle recovery ability was proposed, proving our approach's feasibility.

Designable Electrical/Thermal Coordinated Dual-Regulation Based on Liquid Metal Shape Memory Polymer Foam for Smart Switch.

Electronic components with tunable resistance, especially with synergistic regulation of thermal conductivity, play important roles in the fields of electronics, smart switch, soft robots, and so on. However, it is still a challenge to get the material with various resistance and thermal conductivity stably without lasting external force. Herein, a liquid metal shape memory polymer foam (LM-SMF) is developed by loading electrically and thermally conductive liquid metal (LM) on deformable foam skeleton. Based on thermal response shape memory effect, the foam skeleton can be reversibly pressed, the process of which enables LM to transfer between connected and disconnected states. As a result, obtained LM-SMF shows that the resistance stably changes from 0.8 Ω (conductor) to 200 MΩ (insulator), and the thermal conductivity difference is up to 4.71 times (0.108 to 0.509 W m-1 K-1 ), which indicates that LM-SMF can achieve the electrical and thermal dual-regulation. Moreover, LM-SMF can be used as a designable self-feedback/-warning integrated smart switch or tunable infrared stealth switch. This work proposes a novel strategy to get the material with electrical-thermal coordinated dual-regulation, which is possibly applied in intelligent heating system with real-time monitoring function, electrothermal sensor in the future.

Super-Slippery Poly(Dimethylsiloxane) Brush Surfaces: From Fabrication to Practical Application.

Superwetting surfaces with special slippery performances have been the focus of practical applications and basic research for decades. Compared to superhydrophobic/superoleophobic and slippery liquid-infused porous surfaces (SLIPS), liquid-like covalently attached poly(dimethylsiloxane) (PDMS) brush surfaces have no trouble in constructing the micro/nanostructure and the loss of infused lubricant, meanwhile, it can also provide lots of new advantages, such as smooth, transparent, pressure- and temperature-resistant, and low contact angle hysteresis (CAH) to diverse liquids. This paper focuses on the relationship between the wetting performance and practical functional application of PDMS brush surfaces. Recent progress of the preparation of PDMS brush surfaces and their super-slippery performances, with a special focus on diverse functional applications were summarized. Finally, perspectives on future research directions are also discussed.

Slippery Shape Memory Tube for Smart Droplet Transportation.

Recently, research about controllable droplet transportation in tubes has aroused increased interest. However, existing strategies mainly depend on the elastic tube's shape variation that needs constant external stimuli. Meanwhile, these reported tubes are only suitable for wetting liquids. To achieve the transportation of diverse liquids, different coatings are needed to modify the tube's inner surface to realize complete wetting of different liquids. Herein, we advance a design principle by combining a shape memory polymer (SMP) tube and Nepenthes pitcher plant-inspired slippery surface, which can solve the above-mentioned problems. The SMP offers a tunable tube shape owing to its shape memory effect (SME); the slippery surface reduces the adhesion and expands the applicable range of liquids. Transportation of both water and oils in a wide range of surface tension values can be smartly controlled. The results show that not only the transportation speed and direction can be adjusted but also diverse modes including round-trip transportation, segmented transportation, and antigravity transportation can be achieved. Moreover, applications of the tube in batch inspection of different droplets and step-by-step control of multiple microreactions are also displayed. This work reports a strategy for droplet transportation control based on the tube's SME, which initiates some fresh ideas for designing new superwetting materials toward smart liquid transportation.

Self-Transportation of Superparamagnetic Droplets on a Magnetic Gradient Slippery Surface with On/Off Sliding Controllability.

Recently, research about droplet self-transportation on slippery surfaces has become a hotspot. However, to achieve on/off sliding control during the self-transportation process is still difficult. Herein, we report a magnetic slippery surface, and demonstrate on/off sliding control during the self-transportation of superparamagnetic droplets. The surface is prepared through integrating a substrate that has a gradient magnetic region with a layer of paraffin infused hydrophobic SiO2 nanoparticles. On the surface, a superparamagnetic droplet is pinned at room temperature (about 25 °C), while it can self-transport directionally as the temperature is increased to about 70 °C. When the temperature is cooled down again, the droplet would return to the pinned state, indicating that on/off sliding control during the self-transportation process can be achieved. Furthermore, based on the excellent controllability, controllable coalescence of two droplets from opposite direction is displayed, demonstrating its potential application in numerous areas.

Controllable Droplet Sliding on a Smart Shape-Memory Slippery Surface.

Recently, slippery surfaces with controllable droplet sliding have aroused much attention in both fundamental research and realistic applications. However, for almost all existing surfaces, constant stimuli such as heat, light, magnetic field, etc., are indispensable. Herein, by constructing pit structures on a shape memory polymer and further infusing oil with low surface tension, we report a shape memory slippery surface that can overcome the above imperfection. Based on the shape memory performance, the surface can memorize a diverse pit size as the surface is stretched or recovered. With the variation of pit structure, the sliding performances for both water and organic liquid droplets can be reversibly adjusted between the rolling and pinning states. This work, based on the shape memory effect, reports smart droplet sliding control through regulating the surface microstructure, which not only provides a strategy for droplet sliding control, but also offers some ideas for designing novel intelligent slippery surfaces.

Electrically Induced Underwater Superaerophilicity/Superaerophobicity Switching on Polypyrrole-Coated Mesh Films for Selective Bubble Permeation.

Recently, materials with controllable superwettability have attracted much attention. However, almost all studies focused on controlling wetting of water and oil; research on underwater gas bubble wetting control is still rare. Herein, we report a mesh film prepared by coating polypyrrole (PPy) film on Ti mesh. Briefly, the film mesh is underwater superaerophilic when PPy is doped with perfluorooctanesulfonate ions (PFOS- ), and becomes underwater superaerophobic as the PFOS- are removed. The transition of the wettability can be triggered by electrical stimuli, which is attributed to the cooperative effect between the rough structure and chemical components variation. The controllable wettability allows adjustable bubble permeation. It can be envisioned that the film will provide potential applications in the future, such as underwater bubble capture/release and microfluidic devices.

Underoil Directional Self-Transportation of Water Droplets on a TiO2-Coated Conical Spine.

Directional self-transportation of tiny droplets is significant in many fields. However, almost all existing studies focus on the phenomenon in air, and to realize similar performance in complex environments, such as oil, is still extremely rare. Here, we report a TiO2-coated conical spine (TCS) and demonstrate underoil directional self-transportation of water droplets on its surface. It is found that high surface hydrophilicity resulting from UV irradiation is necessary to achieve the self-transportation of water in oil. The critical water contact angle in oil is about 57°, and the maximal transport velocity can reach 1.4 mm/s. Mechanism analysis reveals that the excellent self-transportation property is ascribed to the combined effect between the Laplace force (FL) caused by the conical gradient structure and the hysteresis reduction resulting from the high hydrophilicity. Moreover, based on the special underoil self-transportation performance, a droplet-based microreaction and demulsification of water-in-oil emulsions were demonstrated using the TCS. This work reports the self-transportation of water in oil, which could provide some fresh ideas for designing new superwetting self-transportation materials.

Fabrication of ulcer-adhesive oral keratin hydrogel for gastric ulcer healing in a rat.

Hydrogel has been used for in suit gastric ulcer therapy by stopping bleeding, separating from ulcer from gastric fluids and providing extracellular matrix scaffold for tissue regeneration, however, this treatment guided with endoscopic catheter in most cases. Here, we developed an oral keratin hydrogel to accelerate the ulcer healing without endoscopic guidance, which can specially adhere to the ulcer because of the high-viscosity gel formation on the wound surface in vivo. Approximately 50% of the ulcer-adhesive keratin hydrogel can resident in ethanol-treated rat stomach within 12 h, while approximately 18% of them maintained in health rat stomach in the same amount of time. Furthermore, Keratin hydrogels accelerated the ethanol-induced gastric ulcer healing by stopping the bleeding, preventing the epithelium cells from gastric acid damage, suppressing inflammation and promoting re-epithelization. The oral administration of keratin hydrogel in gastric ulcer treatment can enhance the patient compliance and reduce the gastroscopy complications. Our research findings reveal a promising biomaterial-based approach for treating gastrointestinal ulcers.

Constructing Scalable Superhydrophobic Membranes for Ultrafast Water-Oil Separation.

Superhydrophobic membranes are desirable for separation of water-in-oil emulsions, membrane distillation, and membrane condensation. However, the lack of large-scale manufacture methods of superhydrophobic membranes hampers their widespread applications. Here, a facile method of coaxial electrospinning is provided to manufacture superhydrophobic membranes for the ultrafast separation of water-in-oil emulsions. Under the high-voltage electric field, the polydimethylsiloxane (PDMS)-coated polyvinylidene fluoride (PVDF) nanofibers and PDMS microspheres with PVDF nanobulges were integrated together during the electrospinning process. Moreover, asymmetric composite membranes with selective layers are designed to reduce the resistance of the mass transfer. Consequently, the as-prepared asymmetric composite membrane exhibits an ultrafast permeance and excellent separation efficiency of about 99.6%, outperforming most of the state-of-the-art membranes reported previously. Most importantly, the membrane could be as large as 770 cm2, could be manufactured continuously, and could be easily enlarged further via tailoring the roller receptor, showing strong promise in the separation of water-in-oil emulsions.

Superwetting Shape Memory Microstructure: Smart Wetting Control and Practical Application.

Smart control of wettability on superwetting surfaces has aroused much attention in the past few years. Compared with traditional strategies such as adjusting the surface chemistry, regulating the surface microstructure is more difficult, though it can bring lots of new functions. Recently, it was found that, based on the shape memory effect of a shape memory polymer, the surface microstructure can be controlled more easily and precisely. Here, recent developments in the smart control of wettability on superwetting shape memory microstructures and corresponding applications are summarized. The primary concern is the superhydrophobic surfaces that have demonstrated numerous attractive functions, including controllable droplet storage, transportation, bouncing, capture/release, and reprogrammable gradient wetting, under variation of the surface microstructure. Finally, some achievements in wetting control on other superwetting surfaces (such as superomniphobic surfaces and superslippery surfaces) and perspectives on future research directions are also discussed.

Molecular basis of nucleosomal H3K36 methylation by NSD methyltransferases.

Histone methyltransferases of the nuclear receptor-binding SET domain protein (NSD) family, including NSD1, NSD2 and NSD3, have crucial roles in chromatin regulation and are implicated in oncogenesis1,2. NSD enzymes exhibit an autoinhibitory state that is relieved by binding to nucleosomes, enabling dimethylation of histone H3 at Lys36 (H3K36)3-7. However, the molecular basis that underlies this mechanism is largely unknown. Here we solve the cryo-electron microscopy structures of NSD2 and NSD3 bound to mononucleosomes. We find that binding of NSD2 and NSD3 to mononucleosomes causes DNA near the linker region to unwrap, which facilitates insertion of the catalytic core between the histone octamer and the unwrapped segment of DNA. A network of DNA- and histone-specific contacts between NSD2 or NSD3 and the nucleosome precisely defines the position of the enzyme on the nucleosome, explaining the specificity of methylation to H3K36. Intermolecular contacts between NSD proteins and nucleosomes are altered by several recurrent cancer-associated mutations in NSD2 and NSD3. NSDs that contain these mutations are catalytically hyperactive in vitro and in cells, and their ectopic expression promotes the proliferation of cancer cells and the growth of xenograft tumours. Together, our research provides molecular insights into the nucleosome-based recognition and histone-modification mechanisms of NSD2 and NSD3, which could lead to strategies for therapeutic targeting of proteins of the NSD family.

Superhydrophobic Shape Memory Polymer Microarrays with Switchable Directional/Antidirectional Droplet Sliding and Optical Performance.

Bioinspired smart surfaces with switchable wettability and optical performance have aroused much attention in the past few years. However, almost all reported surfaces focused on regulating single surface function. In this work, inspired by the butterfly wings, a novel superhydrophobic surface with shape memory polymer microarrays (SMPAs) was prepared through the integration of three-dimensional printing, replica-molding, and a simple surface treatment. In this superhydrophobic SMPA system, the permanent upright microarrays and temporary tilted microarrays can be reversibly switched owing to the excellent shape memory effect (SME). Accompanied by the structure variations, switchable directional/antidirectional droplet sliding and vivid color conversion as the butterfly wings can be achieved. Moreover, because of the SME, local structure regulation can also be achieved on the surface, and with the help of such an ability, the SMPA was further applied as a multifunctional platform to demonstrate controllable droplet transportation and information storage. This work reports the reversible control of directional/antidirectional droplet sliding and tunable color on a superhydrophobic SMPA, and it is believed that such a smart surface can be potentially applied in many fields, such as microfluidic devices and smart optical chips.