Effect of Pore Size, Lubricant Viscosity, and Distribution on the Slippery Properties of Infused Cement Surfaces

The fabrication of slippery liquid-infused porous surfaces (SLIPS) usually requires the use of structured substrates, with specifically designed micro- and nanoroughness and complementary surface chemistry, ideally suited to trap lubricants. It is not yet established whether a random roughness, with a range of pores with a variable size reaching deep into the bulk of the material, is suitable for successful infusion. In this study, a highly porous material with random and complex roughness, obtained by using portland cement (the most common type of cementitious material), was tested for its potential to act as a SLIP surface. Atomic force microscopy meniscus measurements were used to investigate the distribution of lubricants on the surface upon subsequent stages of depletion because of the capillary absorption of the lubricant within the porous structure. Factors such as curing time of the cement paste, time since infusion, and lubricant viscosity were varied to identify the conditions under which infusion could be considered successful. A sensitive method to evaluate the penetration of liquid (low-temperature differential scanning calorimetry) was used, which could be applicable to many porous materials. The optimized infusion of cement surfaces ultimately resulted in the desired hallmarks of SLIPS, that is, high water repellence and slipperiness, effective for several weeks, reduced water permeability, and icephobicity

Distribution and Depletion of Lubricant on Anti-Fouling Lubricant-Infused Surfaces

Lubricant-infused surfaces (LIS), which immobilise a liquid layer on a solid surface, combine the properties of both the liquid and solid surface. These surfaces are exceptionally slippery – droplets easily roll off them, bacteria cannot settle on them, ice cannot adhere to them. Lubricant-infused surfaces represent a paradigm shift in the study of functional surfaces, with the past decade seeing thousands of papers published on the design, application, function and analysis of these surfaces. One particularly exciting avenue of research is the their ability to repel biofouling without the use of banned toxic biocides such as tributyltin (TBT). Unfortunately, the lubricant layer is not entirely immobilised and depletes over time and due to external forces. This Thesis explores the marine antifouling properties of LIS and relates it to the quantity and distribution of lubricant on the surface by developing techniques to quantify and map the lubricant on the surface. The antifouling performance of LIS is tested against marine bacteria, Psuedoalteromonas spp., and in a real-world test. The antifouling ability of these LIS are then related to the amount of lubricant present by measuring the volume of lubricant using a fluorescence technique. To further explore the effect of depletion, the distribution of lubricant is mapped using atomic force microscopy (AFM) meniscus force measurements which allow for precise mapping of the thickness of lubricant at the nanoscale. Using this technique, the antifouling performance of LIS is directly related to the distribution of lubricant on the surface and the effect of different depleting forces on LIS are studied. Specifically, the effect of passing through the air-water interface (unavoidable if deployed in marine environments) is studied, showing that capillarity is the main driving force in stabilising lubricant against this depletion force

Depletion of the Lubricant from Lubricant-Infused Surfaces due to an Air/Water Interface

Lubricant-infused surfaces (LIS) have emerged as an innovative way to combat several modern challenges such as biofouling, ice formation, and surface drag. The favorable properties of LIS are dependent on the presence and distribution of a lubricant layer coating the underlying substrate. Unfortunately, this layer is not indefinitely stable and depletes due to external forces. Here, we study how an air/water interface depletes the lubricant from LIS as a function of lubricant wettability on the substrate by varying the chemistry of both the lubricant and the substrate. The lubricants were chosen to represent some of those most commonly used in the literature (silicone oil, perfluoropolyethers, and mineral oil). We use an optical Wilhelmy plate tensiometer to measure the contact angle of the air/water interface on the LIS in situ as the sample is driven through the air/water interface and contact angle hysteresis as a qualitative measure of lubricant depletion. This data is augmented with ex situ quantitative mapping of lubricant thickness using atomic force microscopy (AFM) meniscus force measurements. We find that a thick layer of excess lubricant is always removed in just one dip, regardless of wettability, and that lubricants that do not spread fully on the substrate deplete faster due to their dewetting into droplets. We also find that lubricants that spread onto the air/water interface are more susceptible to depletion. Finally, we investigate the effect of repeated immersions on the properties of liquid-like poly(dimethylsiloxane) (PDMS) chains tethered to glass and find that dynamic contact angles on these surfaces remain constant over several dips and therefore their low hysteresis is unlikely due to unbound polymer

Life and death of liquid-infused surfaces: a review on the choice, analysis and fate of the infused liquid layer

Liquid-infused surfaces (or lubricant-infused surfaces) (LIS) are a new class of functional materials introduced in 2011. Their exceptional properties have earned them a place at the forefront of many fields including anti-biofouling, anti-icing, anti-corrosion, drag reduction, droplet manipulation and drop-wise condensation. Integral to their success is the infused lubricant layer which affords them their properties. In this review, we examine the current state of the literature relating to the lubricant layer. We consider the lubricant through all stages in the surface’s lifecycle from design, to use, all the way through to depletion and eventual failure. First, we examine trends in lubricant choice and how to choose a lubricant, including environmental and medical considerations. We then look at the different methods used to infuse lubricant into surfaces and how lubricant depletes from the surface. We then report direct and indirect methods to characterise the thickness and distribution of the lubricant layer. Finally, we examine how droplets interact with LIS and the unique properties afforded by the lubricant before providing an outlook into where research centred on understanding the lubricant layer is heading in the new decade

Marine Antifouling Behavior of Lubricant-Infused Nanowrinkled Polymeric Surfaces

A new family of polymeric, lubricant-infused, nanostructured wrinkled surfaces was designed that effectively retains inert nontoxic silicone oil, after draining by spin-coating and vigorous shear for 2 weeks. The wrinkled surfaces were fabricated using three different polymers (Teflon AF, polystyrene, and poly­(4-vinylpyridine)) and two shrinkable substrates (Polyshrink and shrinkwrap), and Teflon on Polyshrink was found to be the most effective system. The volume of trapped lubricant was quantified by adding Nile red to the silicone oil before infusion and then extracting the oil and Nile red from the surfaces in heptane and measuring by fluorimetry. Higher volumes of lubricant induced lower roll-off angles for water droplets, and in turn induced better antifouling performance. The infused surfaces displayed stability in seawater and inhibited growth of <i>Pseudoalteromonas spp</i>. bacteria up to 99%, with as little as 0.9 μL cm^–2 of the silicone oil infused. Field tests in the waters of Sydney Harbor over 7 weeks showed that silicone oil infusion inhibited the attachment of algae, but the algal attachment increased as the silicone oil was slowly depleted over time. The infused wrinkled surfaces have high transparency and are moldable, making them suited to protect the windows of underwater sensors and cameras

Oil Recovery from Nanoporous Media via Water Condensation

Oil?nanoporous materials interplay is ubiquitous in oil recovery from unconventional reservoirs, environmental clean-up, and membrane technology, so there is a genuine need for novel approaches that can monitor, manipulate, and also extract the oil present in nanoporous media. Here demonstrated is a water condensation?assisted method of extracting oil from nanopores. Under cooling-induced condensation at room conditions, distinctive droplet modes act as both decoupling and collecting elements to transport oil from the pore space toward the nanomaterial surface after water evaporation. Even the movement of the oil through the nanoporous network can be visualized by taking advantage of the interference response of visible light in a nanoporous thin-film platform. The method and results presented in this work open different routes to exploit oil?water?nanopore interactions and enable novel perspectives for oil recovery and environmental clean-up.Fil: Gimenez, Rocio Aldana. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; ArgentinaFil: Berli, Claudio Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Bellino, Gabriel Martín. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; Argentin