Liquid-infused Slippery Surfaces Research Articles

Slippery Graphene-Bridging Liquid Metal Layered Heterostructure Nanocomposite for Stable High-Performance Electromagnetic Interference Shielding.

Gallium-based liquid metal (LM) with intriguing high electrical conductivity and room-temperature fluidity has attracted substantial attention for its potential application in flexible electromagnetic interference (EMI) shielding. However, the EMI shielding performance of the existing LM-based composites is unsatisfying due to the irreconcilable contradiction between high EMI shielding efficiency (SE) and low thickness. In addition, the research on environmentally stable EMI shielding material has become an urgent need due to the increasingly sophisticated application scenarios. Herein, we prepared a reduced graphene oxide (rGO) bridging LM layered heterostructure nanocomposite with the liquid-infused slippery surface (S-rGO/LM), which exhibits an ultrahigh X-band EMI SE of 80 dB at a mere internal thickness of 33 μm, and an extremely high value of 100 dB at an internal thickness of 67 μm. More significantly, protected by the ultrathin (2 μm) yet effective slippery surface, the S-rGO/LM film exhibits exceptional EMI shielding stability (EMI SE stays above 70 dB) after enduring various harsh conditions (harsh chemical environments, extreme operating temperatures, and severe mechanical wearing). Moreover, the S-rGO/LM film also demonstrates satisfying photothermal behavior and excellent Joule heating performance (surface temperature of 179 °C at 1.75 V, thermal response <10 s), which endows it with the capability of anti-icing/de-icing. This work proposes a way to construct an LM-based nanocomposite with reliable high-performance EMI shielding capability, which shows great potential for applications in wearable devices, defense, and aeronautics and astronautics.

Droplet Manipulation on Bioinspired Slippery Surfaces: From Design Principle to Biomedical Applications.

Droplet manipulation with high efficiency, high flexibility, and programmability, is essential for various applications in biomedical sciences and engineering. Bioinspired liquid-infused slippery surfaces (LIS), with exceptional interfacial properties, have led to expanding research for droplet manipulation. In this review, an overview of actuation principles is presented to illustrate how materials or systems can be designed for droplet manipulation on LIS. Recent progress on new manipulation methods on LIS is also summarized and their prospective applications in anti-biofouling and pathogen control, biosensing, and the development of digital microfluidics are presented. Finally, an outlook is made on the key challenges and opportunities for droplet manipulation on LIS.

Oil-Grafted Track-Assisted Directional Transport of Water Droplets and Submerged Air Bubbles on Solid Surfaces

Wettability-tailored tracks are emerging as an efficient approach to collecting and transporting underwater air bubbles as well as water from the mist. However, tailoring the surface wettability by modifying the surface structural features via physiochemical methods to create superhydrophilic-superhydrophobic contrast tracks suffers from long-term durability issues, while the emerging liquid-infused slippery surface has inherent design engineering limitations and issues from infused oil depletion. Herein, we demonstrate that by selective silicone oil grafting onto the glass substrate, it is possible to create a wettability contrast of ∼ 43°. Further, we illustrate the application of such tracks for underwater air bubble capturing and transportation in an aqueous medium with surface tension ranging from 72 to 43.5 mN/m. In addition, the potential of these nonadhesive and adhesive tracks for water collection from the mist is shown and the critical effect of the track dimension and intertrack spacing on the water harvesting rate is investigated in detail. The study illustrates that the nonadhesive nature of the oil-grafted region enables the easy transport of underwater air bubbles as well as water from the flow medium and thus offers an easy and facile approach to creating substrates for underwater air bubble collection and water harvesting.

Nontoxic Liquid-Infused Slippery Coating Prepared on Steel Substrates Inhibits Corrosion and Biofouling Adhesion.

Wetting of surfaces plays a vital role in many biological and industrial processes. There are several phenomena closely related to wetting such as biofouling and corrosion that cause the deterioration of materials, while the efforts to prevent the degradation of surface functionality have spread over several millennia. Antifouling coatings have been developed to prevent/delay both corrosion and biofouling, but the problems remain unsolved, influencing the everyday life of the modern society in terms of safety and expenses. In this study, liquid-infused slippery surfaces (LISSs), a recently developed nontoxic repellent technology, that is, a flat variation of omniphobic slippery liquid-infused porous surfaces (SLIPSs), were studied for their anti-corrosion and marine anti-biofouling characteristics on metallic substrates under damaged and plain undamaged conditions. Austenitic stainless steel was chosen as a model due to its wide application in aquatic environments. Our LISS coating effectively prevents biofouling adhesion and decays corrosion of metallic surfaces even if they are severely damaged. The mechanically robust LISS reported in this study significantly extends the SLIPS technology, prompting their application in the marine environment due to the synergy between the facile fabrication process, rapid binding kinetics, nontoxic, ecofriendly, and low-cost applied materials together with excellent repellent characteristics.

Self-healing dual biomimetic liquid-infused slippery surface in a partition matrix: Fabrication and anti-corrosion capability for magnesium alloy

Biomimetics affords versatile ways to develop new routes for protecting metals from corrosion. In this report, focusing on the inhibition of corrosion for magnesium alloy, different biomimetic strategies were studied. Using a facile immersion method followed by surface modification, a lotus leaf-inspired superhydrophobic surface (SHS) is achieved. However, in the water phase, the SHS is found to be vulnerable, and a hydrophilic defect spot can irreversibly deteriorate the corrosion inhibition capability. Based on the infusion of dimethyl silicone oil into a SHS matrix, a dual biomimetic slippery liquid-infused porous surface (SLIPS) in a partition matrix inspired by both Nepenthes pitcher and pomegranate fruit was prepared. In a 3.5 wt% NaCl solution, the corrosion resistance of the SLIPS is found to be four orders of magnitude larger than that of the untreated and superhydrophobic magnesium alloys. In comparison with the vulnerable SHS, the SLIPS can tolerate repeat mechanical damage, exhibiting prominent self-healing properties. A facile route leads to dual biomimetic slippery liquid-infused surface in partition matrix onto magnesium alloy. Slippery liquid-infused porous surface has long-term corrosion inhibition and good self-healing capability. • Immersion and surface modification leads to superhydrophobic AZ31B. • Durability of superhydrophobicity is short for corrosion inhibition. • Slippery liquid-infused porous surface protects AZ31B from corrosion.

Non-wetting Liquid-Infused Slippery Paper.

Liquid-infused slippery surfaces have replaced structural superhydrophobic surfaces in a plethora of emerging applications, hallmarked by their favorable self-healing and liquid-repelling characteristics. Their ease of fabrication on different types of materials and increasing demand in various industrial applications have triggered research interests targeted toward developing an environmental-friendly, flexible, and frugal substrate as the underlying structural and functional backbone. Although many expensive polymers such as polytetrafluoroethylene have so far been used for their fabrication, these are constrained by their compromised flexibility and non-ecofriendliness due to the use of fluorine. Here, we explore the development and deployment of a biodegradable, recyclable, flexible, and an economically viable material in the form of a paper matrix for fabricating liquid-infused slippery interfaces for prolonged usage. We show by controlled experiments that a simple silanization followed by an oil infusion protocol imparts an inherent slipperiness (low contact angle hysteresis and low tilting angle for sliding) to the droplet motion on the paper substrate and provides favorable anti-icing characteristics, albeit keeping the paper microstructures unaltered. This ensures concomitant hydrophobicity, water adhesion, and capillarity for low surface tension fluids, such as mustard oil, with an implicit role played by the paper pore size distribution toward retaining a stable layer of the infused oil. With demonstrated supreme anti-icing characteristics, these results open up new possibilities of realizing high-throughput paper-based substrates for a wide variety of applications ranging from biomedical unit operations to droplet-based digital microfluidics.

Investigation of vulcanization fouling behavior of biomimetic liquid-infused slippery surfaces

Investigation of vulcanization fouling behavior of biomimetic liquid-infused slippery surfaces

Liquid‐Infused Slippery Stainless Steel Surface Prepared by Alcohol‐Assisted Femtosecond Laser Ablation

AbstractNepenthes‐inspired liquid‐infused slippery surface (LISS) attracts great attention because it can repel different kinds of liquid and shows great stability. However, the vast majority of LISSs are realized on polymer materials which limit the applications. Here, a kind of universal method to directly construct porous micro/nanostructures on any kind of materials to realize LISS is put forward. As an example, abundant micro/nanohole structures are built on stainless steel surface by alcohol‐assisted femtosecond laser ablation. Then, LISS is achieved on stainless steel, which shows slippery property to variety of liquid with different chemical composition. The velocity of water droplet slipping on LISS can be tuned by water droplet volume, LISS tilt angle, and lubricant type. Some potential applications of the LISS are demonstrated by some simple experiments. Flexible movement of magnetic water droplet is realized on the LISS by controlling magnetic field. The LISS shows good antifouling performance to green alga. Moreover, the porous structures are very stable in different harsh environments. This alcohol‐assisted femtosecond laser irradiation method successfully constructs porous micro/nanostructures on different kinds of materials. Thus, this work can promote the applications of LISS in droplet manipulation, microfluidics, antifouling surface, and so on.

Novel multifunctional solid slippery surfaces with self-assembled fluorine-free small molecules

Functional slippery surfaces have broad applications in engineering and bioengineering processes, such as water harvesting, photocatalysis, wastewater treatment and food industry. In this work, for the first time, we report the fabrication of a novel type of functional slippery solid surfaces via the self-assembly of a non-fluorine small molecule, γ-mercaptopropyldi(trimethylsiloxy)methylsilane (MD(SH)M), which possess liquid-like slippery features. This new strategy avoids the requirement and fabrication of complex micro-/nano-scale surface structures and infused lubricant oils in conventional slippery surfaces. The as-prepared functional MD(SH)M surfaces allow facile transport of bubbles in aqueous media and water drops in oil, as well as facilitate the self-assembly of nanoparticles from their aqueous suspensions. The transport of air bubbles and water drops is driven by the buoyancy force or gravity force, against the sliding resistance associated with the bubble-solid-water or drop-solid-oil three-phase contact line. The functional slippery surfaces with lower surface energy and contact angle hysteresis show higher velocity of transporting bubbles/drops under the same test conditions, demonstrating better slippery behavior. The as-prepared functional slippery solid surfaces allow the three-phase contact line to move more freely as compared to the conventional lubricant liquid-infused slippery surfaces. This research provides a new and facile strategy for the fabrication of novel slippery coatings without the need of complex micro-/nano-scale surface structures and infused lubricant oils, with great potential applications in many engineering and bioengineering processes wherever low friction forces are desired.

Field-Induced Wettability Gradients for No-Loss Transport of Oil Droplets on Slippery Surfaces.

Transporting oil droplets is crucial for a wide range of industrial and biomedical applications but remains highly challenging due to the large contact angle hysteresis on most solid surfaces. A liquid-infused slippery surface has a low hysteresis contact angle and is a highly promising platform if sufficient wettability gradient can be created. Current strategies used to create wettability gradient typically rely on the engineering of the chemical composition or geometrical structure. However, these strategies are inefficient on a slippery surface because the infused liquid tends to conceal the gradient in the chemical composition and small-scale geometrical structure. Magnifying the structure, on the other hand, will significantly distort the surface topography, which is unwanted in practice. In this study, we address this challenge by introducing a field-induced wettability gradient on a flat slippery surface. By printing radial electrodes array, we can pattern the electric field, which induces gradient contact angles. Theoretical analysis and experimental results reveal that the droplet transport behavior can be captured by a nondimensional electric Bond number. Our surface enables no-loss transport of various types of droplets, which we expect to find important applications such as heat transfer, anticontamination, microfluidics, and biochemical analysis.

An ionic liquid-infused slippery surface for temperature stability, shear resistance and corrosion resistance

The stability of slippery liquid-infused porous surfaces (SLIPSs) is of great significance in long-term applications.

Oil-Infused Silicone Prevents Zebra Mussel Adhesion

The remarkable underwater adhesion capacity of the invasive freshwater mussel species Dreissena polymorpha (zebra mussel) causes extensive damage each year. The adhesive interface between the substrate surface and the mussels' adhesive plaques plays a key role in zebra mussel biofouling. Silicone-oil-infused polydimethylsiloxane (iPDMS), an omniphobic material in the class of liquid-infused slippery surfaces, has been shown to develop a uniform, microscale, antifouling surface oil layer, which we hypothesized would be effective against zebra mussel fouling. iPDMS substrates with varying levels of oil saturation were tested for their ability to disrupt mussel adhesion by characterizing zebra mussel reattachment in a simulated freshwater environment for 3 days. On fully saturated iPDMS samples or those near full saturation, zebra mussels showed no reattachment, compared to 41% reattachment on PDMS controls (no oil infusion). For lower saturation levels, the frequency of reattachment was decreased relative to PDMS controls. Mussel detachment forces decreased in iPDMS as compared to PDMS, and adhesive failures occurred more frequently with higher iPDMS saturations. Surface analysis of the subsaturated iPDMS substrates showed incomplete coverage of the surface oil layer. After 3 days of immersion in artificial freshwater, subsaturated iPDMS substrates showed a decrease in slipperiness (measured by water slide angle), whereas in fully saturated iPDMS, the slipperiness was unchanged, despite no observed oil loss in either group. The decrease in slipperiness is attributed to microfouling of the subsaturated substrates, consistent with incomplete surface oil layer coverage, and supports the notion that full oil layer coverage is required for effective antifouling properties. Employing iPDMS as an antifouling coating shows promise against freshwater mussel adhesion, and this work further aids in understanding the antifouling mechanism of iPDMS and the role of the plaque-substrate interface in freshwater mussel adhesion.

Facile fabrication of biomimetic liquid-infused slippery surface on carbon steel and its self-cleaning, anti-corrosion, anti-frosting and tribological properties

Herein, facile and commercial nanosecond laser treatment was utilized to fabricate biomimetic liquid-infused slippery surface on carbon steel, and its self-cleaning, anti-corrosion, anti-frosting and tribological properties were systematically analyzed. The SEM and three-dimensional morphology analysis results revealed that the laser treatment was effective in producing extreme rough, porous and multilevel surface morphology on steel substrate. After fluorination process and subsequent oil infusion, slippery surface was successfully created. Through wetting analysis, it was found that as-prepared slippery surface showed hydrophobic property with a low contact angle hysteresis, indicating that a uniform and smooth oil layer had been created. Owing to its excellent anti-wetting and insulator effects to liquid medium, slippery surface was proven to behave superior self-cleaning and anti-corrosion performances. Furthermore, slippery surface could also effectively postpone the moisture condensation, which hence endowed steel substrate with enhanced anti-frosting property. Compared with base steel, slippery surface also showed improved friction-reducing and anti-wear performances due to the lubricating effect of oil layer. Based on these results, it could expect that the prepared slippery surface is promising to expand the practical application of traditional carbon steel materials.

Emerging Applications of Bioinspired Slippery Surfaces in Biomedical Fields.

In this minireview, we summarize the recent development of liquid-infused slippery surfaces (LISS) for biomedical applications. The selected topics are divided into two parts: the material designs and emerging strategies to fabricate slippery surface, and their applications with strong and direct relevance to biomedical areas including antibiofouling, antithrombosis, medical device coatings and surface enhanced/assisted detection. We also describe the most critical directions in need of development to adapt this new approach to biomedical use.

Strategies for anti-icing: low surface energy or liquid-infused?

Recent progress on the preparation and surface characteristics of polymeric anti-icing coatings from low surface energy or liquid-infused slippery surfaces is reviewed and illustrated.

Supramolecular Polymers as Surface Coatings: Rapid Fabrication of Healable Superhydrophobic and Slippery Surfaces

Supramolecular polymerization for non-wetting surface coatings is described. The self-assembly of low-molecular-weight gelators (LMWGs) with perfluorinated side chains can be utilized to rapidly construct superhydrophobic, as well as liquid-infused slippery surfaces within minutes. The lubricated slippery surface exhibits impressive repellency to biological li-quids, such as human serum and blood, and very fast self-healing.