Wettability Patterns Research Articles

Surface wettability pattern and shape gradient co-induced oil droplet directional transport for enhancement of lubrication performance

Surface wettability pattern and shape gradient co-induced oil droplet directional transport for enhancement of lubrication performance

Surface modification and patterning of polymer thin films by plasma and adsorption behavior of proteins

The surface wettability property of hydrophobic polystyrene (PS) and hydrophilic polyethylene glycol (PEG) thin films subjected to modification by direct current plasma glow discharge is studied. The polymer films exhibited change of surface wettability on exposure to air, nitrogen, oxygen or argon plasmas. In PS films a swift modification to hydrophilic surface and subsequent steady recovery following first order kinetics are observed. The rate of modification and recovery are adjustable by adjusting the plasma ambient and parameters, and additional wet-chemical treatment using ionic solutions. In PEG films the hydrophobic wettability evolve with ageing following the first order kinetics, and is stable for long period on exposure to air ambient. Moreover, a vapor deposition like process is possible using the PEG films as source to deposit self-assembled molecular layers with hydrophobic wettability on other surfaces. Using surface modification or molecular deposition processes, the fabrication of wettability patterns in the surface of PS and PEG films, and on other surfaces by vapor transport using PEG films, and also the possibility to produce gradient wettability patterns are demonstrated. Moreover, the adsorption behavior of immuno-specific system of proteins on surface modified hydrophilic PS films is studied.

Effects of atmospheric pressure plasma treatment and its aging behaviors on interfacial strength of PI/PEEK composite film

AbstractSince the properties of surface roughness with time and the wettability pattern of polymer surfaces transformed by plasma remain unclear. In order to understand the mechanism of aging effect on film properties, this paper analyzes the aging of plasma‐treated PI films. The optimal treatment conditions were first explored by adjusting the plasma treatment power. Based on the effect of plasma treatment power on the surface physicochemical properties and mechanical properties of PI films. It was found that the content of oxygen‐containing functional groups on the surface of the film was highest at a plasma treatment power of 800 W, and the surface energy reached a maximum value of 67.71 mJ/m2. As the treatment power increases, the surface etching of the PI film increases significantly, as does the roughness. However, if the power is too high, it can cause excessive etching, resulting in peeling of the film surface. In addition, the mechanical properties of the films decreased with increasing plasma treatment power. Based on the effect of plasma treatment power on the surface physicochemical and mechanical properties of PI films, the best overall modification effect of PI films was determined when the treatment power was 800 W and the speed was 6 mm/s. And at 800 W, the peel strength of the PI/PEEK composite film reached a maximum value of 9.55 N/cm, which was 77.84% higher than that of the untreated composite film. However, plasma‐treated PI films can experience surface remodeling after being exposed to air for a period of time. In this paper, the wettability as well as the mechanical properties of the films are analyzed for different aging times. The results showed that after 30 days of plasma treatment, the O/C and N/C contents on the surface of the PI film decreased, and the wettability performance decreased by 19.45% compared with that of the recently treated film.

Multi‐Level Wettability Patterned Porous Matrix for Advanced Optical Information Encryption

AbstractIn the rapidly evolving landscape of information security, the demand for optical encryption techniques based on wettability patterning, which allows decryption without sophisticated devices and complex procedures, is progressively increasing. However, conventional approaches based on binary wettability patterned surfaces impose significant constraints in their practical use for high‐level information security. Herein, a novel approach to optically encrypt information through multi‐level wettability patterning is introduced on a porous polymer matrix synthesized from vinyl methacrylate (VMA) and poly(ethylene glycol) diacrylate (PEGDA). By employing the thiol‐ene click reaction, precise patterning of functional groups is achieved that exhibit distinct wettability responses to aqueous solutions with varying surface tensions, as well as pH‐responsive and fluorescent markers. This multi‐level wettability system surpasses traditional binary hydrophilic/hydrophobic patterns by providing enhanced control over wettability states, resulting in higher‐level encryption of information. The integration of pH and fluorescence responsivity further elevates the complexity and security of the encrypted information, making it decipherable only under specific and controlled conditions. The innovative approach offers a highly secure, robust, and customizable encryption method, redefining the potential of optical encryption technologies.

Mechanobiological mechanisms in the remediation of soil lead pollution using two-dimensional carbon materials and Morchella: A molecular-level study

Graphene-based 2D carbon composites and Morchella mushrooms are used in the paper to study the mechanobiological mechanisms of soil lead remediation. Soil is contaminated with lead, which threatens ecosystems and human health, making it even more important to find remedies. To fully comprehend these processes, present-day materials, and organic compounds are needed to improve soil nutrition and eradicate lead. To deal with the challenge of finding effective means of lead removal; limitations associated with traditional soil pollution remediation methods; and merging biology and material sciences. Multifunctional graphene wettability-patterned nanocoated membranes (MGW-PNM) is a novel technique developed to overcome these challenges. Such processes result in membranes with different wettability patterns that take advantage of the properties of graphene. This facilitates better interaction between the membrane itself and the surrounding soil as well as lead contaminants by modifying its hydrophobicity or hydrophilicity characteristics. For effective removal of lead, extensive simulation studies were done using MGW-PNM. In line with this, it can be inferred that MGW-PNM also remediates highly capable soils at high-efficiency levels. This was established when comparing modern techniques to past ones where considerable improvements were made on how much lead is extracted from them. The study suggests new ways of addressing environmental contamination resulting from microbial activities in soils by combining advanced materials with biological substances such as Morchella spp. For this purpose, it investigates various molecular interactions occurring among carbonaceous species called Morchella microbes and environmental pollutants like those including Pb.

Omniphobic Photoresist‐Assisted Patterning of Porous Polymethacrylate Films

AbstractPatterning of various surface properties, including roughness, wettability, adhesiveness, and mechanical properties, can markedly enhance the functionality of test systems. Thus, porous polymethacrylates prepared by polymerization‐induced phase separation (PIPS) represent a promising class of functional materials for the construction of miniaturized test systems. Different porosity, surface chemistry, and wettability are achieved in porous polymethacrylates with different precursor compositions. Nevertheless, only wettability microstructuring has been highlighted for these materials thus far. Here, the study presents a novel method for the direct and selective deposition of porous polymethacrylate films with different surface chemistry and porosity. The selective adhesion of omniphobic–omniphilic wettability patterns is used to facilitate the polymer pattern formation. The feasibility of patterning with different monomers and porogenic solvents is demonstrated. The topological study confirms the selective application of polymer structures with different thickness and roughness. The wettability characterization of the omniphobic material shows no significant changes caused by the operations performed. Thus, a new pattern with a greater difference in the wettability of the areas is produced in the process. Discontinuous dewetting of different liquids is performed. The use of poly(2‐hydroxyethyl methacrylate‐co‐ethylene dimethacrylate) (HEMA‐EDMA) modified patterns for precise living cell patterning is also demonstrated.

Surface with wettability gradient — A novel approach for crystallization fouling control on the horizontal falling film flow

To manage scaling on heat transfer surfaces, using chemical-based antifouling treatments takes a toll on the environment, and related maintenance costs are significant. A unique and environmentally friendly scale mitigation strategy is developed in this work. By manipulating the scale layer distribution using surface wettability gradients, stronger flow shear and weaker scaling adhesion are achieved, facilitating self-cleaning process. Experimental work utilizes a horizontal-tube falling-film evaporator to mimic multiple-effect distillation process. A millimetric wettability pattern – alternating hydrophilic and hydrophobic regions – is created by coating stainless steel tubes. The results show scale layers (calcium carbonate) were either thicker in hydrophilic regions and thinner in hydrophobic regions or had approximately uniform thickness in both regions but cracks in scale layers near wettability boundaries. Scale layers wash-off with flow is observed on patterned tubes, demonstrating self-cleaning process. In contrast to persistent deterioration in overall HTC (heat transfer coefficient) for baseline tube (77 % of initial HTC after 192 h), HTC on patterned tubes initially increases due to surface wetting effects, then maintains roughly constant (15 % higher than that of baseline after 192 h) along with lower scale mass. This work provides a novel scaling control method, a potential “green” alternative to current industry scale-control practices.

Biphilic Functional Surfaces for Frost Prevention and Efficient Active Defrosting

AbstractThe present work addresses the systematic accurate fabrication and design of biphilic surfaces having superhydrophobic circular islands surrounded by a hydrophilic background by investigating their condensation frosting and defrosting behavior. A significant delay in frost formation is observed on samples with higher superhydrophobicity ratio A*, defined as superhydrophobic area to total area ratio. As the superhydrophobic island diameter D increases from D = 500 µm to D = 700 µm (A* from 19.62% to 38.46%), a 50% improvement/delay is observed in terms of frost formation or densification. Besides delaying icing/frosting, the presence of superhydrophobic areas empowers the formation of porous and nonuniform frost structure, which facilitates ice removal during the defrosting process. To this end, as the surface is recovered the ambient temperature, almost complete passive cleaning performance within only 23 s is observed on the biphilic design having superhydrophobic islands with the diameter of D = 500 µm, that is, a superhydrophobicity ratio A* of 19.62%. This work concludes on the optimum biphilic ratio, which is not only effective as a passive method by hindering frosting but also leads to a slush/water free surface after defrosting eased by the Laplace pressure gradient which is imposed by the different biphilic wettability patterns.

Printed and Laser Induced Graphene Electrochemical Biosensors for Rapid Environmental and Biomedical Monitoring

This presentation will demonstrate how low-cost printed and flexible graphene circuits can overcome the challenges associated with conventional electrical circuits to open the door to a highly sensitive monitoring of biochemical threats and toxins including nerve agents/pesticides. The use of inkjet and aerosol printing; spin coating; and laser writing (i.e., laser induced graphene) can be used to create such circuits with high resolution (line widths as low as 20 µm). Moreover, the use of rapid-pulse laser annealing of the printed graphene and/or salt porogens added into graphene inks before printing can be used to further improve the electrical conductivity (< 10 ohms/sq.) and electroactive surface area (nano/micro structuring) of the graphene circuits as well as be used to tune the surface of the printed graphene from one that is hydrophilic (water contact angle (WCA) = 48°) to one that is superhydrophobic (WCA = 158°). More recently we demonstrate how graphene synthesis, patterning and surface wettability can all be controlled through a laser induced graphene (LIG) process that creates a high surface area graphene surface directly from polyimide. Such LIG circumvents the need to create solution-phase graphene inks for printing. These printing and laser fabrication techniques are also amenable for use on flexible and chemically/thermally sensitive surfaces including polymers and paper.Moreover, the laser etched printed graphene and LIG exhibits an inherent 3D morphology that significantly increases the electrode electroactive surface over traditional 2D planar graphene electrodes. This large increase in surface area significantly improves the loading of enzyme onto the electrode surface and subsequently increases the heterogenous charge transport during catalytic pesticide sensing. Such ion sensors displayed near-Nernstian sensitivities, wide sensing ranges over four orders of magnitude extending from the 10–2 M down to detection limits in the 10–6 M range or for fertilizer ions (nitrate, ammonium, potassium, calcium, and magnesium) reaching down to detection limits less than 1 ppm in some cases in soil and water samples. The pesticide sensing capability of the sensor is able to reach an extremely low picomolar detect limit for organophosphates (paraoxon) and to the nanomolar regime for neonicotinoids in surface waters. We also demonstrate how this flexible LIG electrodes can be coupled with polymeric microfluidics and adhered to the body for continuous monitoring of lactate, glucose, and sodium in the sweat. Finally, we demonstrate how such surface wettability patterning of the printed graphene and LIG itself through laser etching can be used to make hydrophilic LIG tracks surrounded by near superhydrophic sidewalls for open microfluidic fluid transport without the need for polymeric microfluidics. Such open microfluidic tracks enable the splitting and transport of fluid samples to distinct electrochemical sensors for multiplexed biosensing of both fertilizer ion and pesticide monitoring from water samples and assist in harvesting sprayed pesticides in the field. Figure 1

Innovative 3D-printed surfaces for efficient water harvesting from air

PurposeThe purpose of this study is to develop nature-inspired 3D surfaces for atmospheric water harvesting.Design/methodology/approachInitially, cylindrical-shaped protrusions were produced utilizing a 3D printer to obtain a surface with a high surface area. Subsequently, an electrospraying technique was employed to coat the tips of these hydrophobic protrusions with hydrophilic nano-scale particles and fibers, utilizing polyamide 6 (PA6) or PA6/chitosan (CH) blends. In the next stage of the study, the impact of protrusion shape was investigated by fabricating surfaces with cylindrical, conical and tree-shaped protrusions. Following the production of 3D surfaces, PA6 was electrosprayed onto the protrusions to achieve varied wettability patterns on the 3D surface. Finally, the water collection rates and capacities of the surfaces were evaluated.FindingsWater collection tests demonstrated that PA6-coated surfaces exhibited greater water collection capacity compared to untreated surfaces. Furthermore, the addition of CH enhanced the water collecting efficiency of the 3D surface. It was found that the shape of the protrusions significantly influenced water collection capacity. Particularly, cone-shaped protrusions exhibited the highest water collecting capability among the different shapes tested.Originality/valueIn this study, 3D printing and electrospraying techniques were combined to create 3D surfaces characterized by high surface area, along with hydrophilic and hydrophobic regions to produce superior surfaces for atmospheric water harvesting.

‘Rewritable’ and ‘liquid-specific’ recognizable wettability pattern

Bio-inspired surfaces with wettability patterns display a unique ability for liquid manipulations. Sacrificing anti-wetting property for confining liquids irrespective of their surface tension (γLV), remains a widely accepted basis for developing wettability patterns. In contrast, we introduce a ‘liquid-specific’ wettability pattern through selectively sacrificing the slippery property against only low γLV (<30 mN m−1) liquids. This design includes a chemically reactive crystalline network of phase-transitioning polymer, which displays an effortless sliding of both low and high γLV liquids. Upon its strategic chemical modification, droplets of low γLV liquids fail to slide, rather spill arbitrarily on the tilted interface. In contrast, droplets of high γLV liquids continue to slide on the same modified interface. Interestingly, the phase–transition driven rearrangement of crystalline network allows to revert the slippery property against low γLV liquids. Here, we report a ‘rewritable’ and ‘liquid-specific’ wettability pattern for high throughput screening, separating, and remoulding non-aqueous liquids.

Droplet-based mechanical transducers modulated by the symmetry of wettability patterns

Asymmetric mechanical transducers have important applications in energy harvesting, signal transmission, and micro-mechanics. To achieve asymmetric transformation of mechanical motion or energy, active robotic metamaterials, as well as materials with asymmetric microstructures or internal orientation, are usually employed. However, these strategies usually require continuous energy supplement and laborious fabrication, and limited transformation modes are achieved. Herein, utilizing wettability patterned surfaces for precise control of the droplet contact line and inner flow, we demonstrate a droplet-based mechanical transducer system, and achieve multimodal responses to specific vibrations. By virtue of the synergistic effect of surface tension and solid-liquid adhesion on the liquid dynamics, the droplet on the patterned substrate can exhibit symmetric/asymmetric vibration transformation when the substrate vibrates horizontally. Based on this, we construct arrayed patterns with distinct arrangements on the substrate, and employ the swarm effect of the arrayed droplets to achieve three-dimensional and multimodal actuation of the target plate under a fixed input vibration. Further, we demonstrate the utilization of the mechanical transducers for vibration management, object transport, and laser modulation. These findings provide a simple yet efficient strategy to realize a multimodal mechanical transducer, which shows significant potential for aseismic design, optical molding, as well as micro-electromechanical systems (MEMS).

Dissecting wheat above-ground architecture for enhanced water use efficiency and grain yield in the subtropics

BackgroundGrowing wheat under climate change scenarios challenges, scientists to develop drought and heat-tolerant genotypes. The adaptive traits should therefore be explored and engineered for this purpose. Thus, this study aimed to dissect surface traits and optimizing the leaf architecture to enhance water use efficiency (WUE) and grain yield. Twenty-six wheat genotypes were assessed for five novel leaf traits (NLTs: leaf prickle hairs, groove type, rolling, angle and wettability) under normal, drought and heat conditions following triplicated factorial randomized complete block design (RCBD). The data for NLTs, physiological traits (stomatal conductance, WUE, transpiration, and photosynthesis), and standard morphological and yield traits were recorded. Leaves were sampled at the stem elongation stage (Zadoks 34) to measure the leaf water content (%), contact angle, and to obtain pictures through scanning electron microscopy (SEM). The air moisture harvesting efficiency was evaluated for five selected genotypes. The ideotype concept was applied to evaluate the best-performing genotypes.ResultsThe correlation analysis indicated that long leaf prickle hairs (> 100 μm), short stomatal aperture and density (40–60 mm− 2), inward to spiral leaf rolling, medium leaf indentation, low contact angle hysteresis (< 10°), and cuticular wax were positively associated with WUE. This, in turn, was significantly correlated to grain yield. Thus, the genotypes (E-1) with these traits and alternate leaf wettability had maximum grain yield (502 g m− 2) and WUE supported with high photosynthesis rate, and relative water content (94 and 75% under normal and stress conditions, respectively). However, the genotype (1-hooded) with dense leaf hairs on edges but droopy leaves, spiral leaf rolling, and lighter groove, also performed better in terms of grain yield (450 g m− 2) under heat stress conditions by maintaining high photosynthesis and WUE with low stomatal conductance and transpiration rate.ConclusionThe SEM analysis verified that the density of hairs on the leaf surface and epicuticular wax contributes towards alternate wettability patterns thereby increasing the water-use efficiency and yield of the wheat plant. This study paves a way towards screening and and developing heat and drought-tolerant cultivars that are water-saving and climate-resilient.

Wettability patterning of titanium surfaces through pulsed laser melting for enhanced condensation heat transfer

Wettability engineering of different surfaces has been in the spotlight for the last few decades for enhanced condensation heat transfer in various applications. In this study, we experimentally investigated the water vapor condensation on a wettability-tailored Titanium-based (Ti-6Al-4V) grade 5 alloy. We utilize the microsecond laser to texture the surface by melting at various scanning speeds to realize a wide range of scalable surface structures. We further render these surfaces hydrophobic through chemical vapor deposition of silane at atmospheric pressure. Further water vapor condensation experiments are performed on these surfaces. The results show that the increased surface roughness due to laser-based melting altered the surface wettability of the Ti-surface and made it hydrophilic, exhibiting water drop contact angles ranging between 18° and 56° for the scan speeds between 25mm/s and 50 mm/s, respectively. The vapor deposition of silane on laser-melted Ti-surfaces lowered its surface energy and made them hydrophobic, showing contact angles of water drop up to ~106° specifically at lower scan speeds (~ 25 mm/s). Finally, the vapor condensation experiments showed an enhanced amount of condensed water collection with dropwise mode compared to the bare Ti surface due to a change in the wetting nature altered by laser melting.

Molecular Dynamics Study of the Microscopic Mechanical Balance at the Three-Phase Contact Line of Interfacial Nanobubble.

This study reveals the microscopic mechanical balance at the three-phase contact line (TPCL) of an interfacial nanobubble on a substrate with a wettability pattern using molecular dynamics simulations. The apparent contact angle was compared to that evaluated using Young's equation, in which the interfacial tensions were computed using a mechanical route. The comparison was conducted by changing the wettability of the substrate from hydrophilic to neutral while maintaining a hydrophobic region in the center of the substrate. When the wettability pattern pins the TPCL at the wettability boundary, the contact angle computed by Young's equation is larger than the apparent contact angle because a pinning force exists in the inward direction of the nanobubble. Conversely, on the surfaces where the wettability pattern does not pin the TPCL, the contact angle computed by Young's equation agrees with the apparent contact angle because the pinning force disappears. The distribution of principal stresses around the TPCL, which was visualized for the first time in this study, indicates that large compressive principal stresses exist between the liquid phase and the solid substrate interface, which pin the TPCL at the surface wettability boundary, and that the maximum principal stress occurs in the inward direction of the nanobubbles at the TPCL. The normalized pinning force estimated from the maximum principal stress is equivalent to that measured experimentally.

Bio-inspired wettability patterning for flexible and wearable electrochemical immunosensors utilizing PDMS-TiO2 coating

The electrochemical sensor strip presented in this work, designed for low-volume point-of-care immunosensing applications and demonstrated using prostate-specific antigen as an example, exhibits remarkable efficiency by requiring only around 2 μL of sample volume. The decrease in sample amount required is facilitated through the application of nature inspired wettability patterning technique using PDMS-TiO2 nanocomposite coating, which incorporates distinct super-hydrophilic and super-hydrophobic regions on the electrode surface. This surface modification facilitates a highly sensitive antigen detection in minimal sample volumes. The sensor strip demonstrates a linear detection range spanning from 0.0001 to 100 ng mL-1, with a limit of detection of 0.0001 ng mL-1. Additionally, the sensor performance remains consistent across varying inclinations of the sensor strip, ensuring its applicability in the field of wearable sensing. Moreover, the incorporation of the PDMS-TiO2 coating enhances the electrochemical performance of the sensor by providing an extended surface area without introducing electrical interference. A wide range of electrochemical methods, such as cyclic voltammetry, linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy, have been utilized. In support of these experimental findings, simulation studies have explored droplet spreading dynamics upon variation of the droplet size and electrode surface inclination. The developed sensor strip can serve as a promising candidate for practical point-of-care testing applications, expanding its applicability to a broad spectrum of immunosensing applications targeting diverse antigens.

Chemical Instability-Induced Wettability Patterns on Superhydrophobic Surfaces.

Chemical instability of liquid-repellent surfaces is one of the nontrivial hurdles that hinders their real-world applications. Although much effort has been made to prepare chemically durable liquid-repellent surfaces, little attention has been paid to exploit the instability for versatile use. Herein, we propose to create hydrophilic patterns on a superhydrophobic surface by taking advantage of its chemical instability induced by acid solution treatment. A superhydrophobic Cu(OH)2 nanoneedle-covered Cu plate that shows poor stability towards HCl solution (1.0 M) is taken as an example. The results show that 2.5 min of HCl solution exposure leads to the etching of Cu(OH)2 nanoneedles and the partial removal of the self-assembled fluoroalkyl silane molecular layer, resulting in the wettability transition from superhydrophobocity to hydrophilicity, and the water contact angle decreases from ~160° to ~30°. Hydrophilic dimples with different diameters are then created on the superhydrophobic surfaces by depositing HCl droplets with different volumes. Afterwards, the hydrophilic dimple-patterned superhydrophobic surfaces are used for water droplet manipulations, including controlled transfer, merging, and nanoliter droplet deposition. The results thereby verify the feasibility of creating wettability patterns on superhydrophobic surfaces by using their chemical instability towards corrosive solutions, which broadens the fabrication methods and applications of functional liquid-repellent surfaces.

Patterned Manipulated Surface Based on Femtosecond Laser with Adjustable Wetting Speed and Directional Fluid Delivery.

Recently, due to the crucial roles of multifunctional liquid manipulation surfaces in biomedical transportation, microfluidics, and chemical engineering, the demand for controllable and functional aspects of directed liquid transportation has increased significantly. However, designing an intelligent manipulation surface that is easy to manufacture and fully functional remains an immense challenge. To address this challenge, a smart surface that can regulate the rate of liquid transport within a patterned channel by temperature is reported. A synergistically controlled approach of poly(N-isopropylacrylamide) and micropillar shape-memory polymers (SMPs) was used to modulate the wetting rate of liquids on surfaces. By femtosecond laser direct writing, temperature-responsive composite surfaces are embedded in the microstructure of shape-memory polymers (SMPs) in a patterned manner, resulting in the preparation of novel programmable liquid manipulation surfaces incorporating boundaries possessing asymmetric wettability. Since the smart surface is based on SMP, the superhydrophobic part in the superhydrophobic/controllable wettability patterning platform is also programmed for droplet directional transport, which takes advantage of the difference in wettability between the rewritable indentation track and the periphery to allow droplets to flow into the temperature-controlled velocity track, enriching the functionality of the surface. In addition, based on its excellent controllability and patterning, the surface has been shown to be used in microfluidic circuit chips with self-cleaning properties, which provides new ideas for circuit timing control. This study provides promising prospects for the effective development of multifunctional liquid steering surfaces, lab-on-a-chip, and microfluidic devices.

Enhanced boiling heat transfer performance on wettability-patterned surface

As an efficient heat transfer method, boiling heat transfer (BHT) plays an important role in strengthening the thermal management of high-power electronics, etc. In this work, the wettability patterns are prepared on copper substrate by mask-assisted chemical processing method, which enhances the BHT performance. We firstly treat the copper surface into superhydrophilic by chemical immersion, and then it is modified by fluorosilane into superhydrophobic, and wettability patterns are formed with the assistance of mask. Then, the BHT performances and the corresponding bubble dynamics of the wettability-patterned surfaces are experimentally investigated. Finally, the optimal BHT performances of the wettability-patterned surface prepared by the proposed method are compared with other modified surfaces. The results show that the BHT is improved dramatically on the wettability-patterned surface, the critical heat flux (CHF) and the heat transfer coefficient (HTC) improve by 23% and 56%, respectively. Under high heat flux, the decrease of hydrophobic pattern size can significantly improve the BHT performances, while under low heat flux, reducing the hydrophobic pattern pitch can improve the BHT performances to a certain extent. The reduction of the hydrophobic area has a significant effect on the CHF and HTC.

Microsphere-Enabled Micropillar Array for Whispering Gallery Mode Virus Detection.

Rapid detection of pathogens and analytes at the point of care offers an opportunity for prompt patient management and public health control. This paper reports an open microfluidic platform coupled with active whispering gallery mode (WGM) microsphere resonators for the rapid detection of influenza viruses. The WGM microsphere resonators, precoated with influenza A polyclonal antibodies, are mechanically trapped in the open micropillar array, where the evaporation-driven flow continuously transports a small volume (∼μL) of sample to the resonators without auxiliaries. Selective chemical modification of the pillar array changes surface wettability and flow pattern, which enhances the detection sensitivity of the WGM resonator-based virus sensor. The optofluidic sensing platform is able to specifically detect influenza A viruses within 15 min using a few microliters of sample and displays a linear response to different virus concentrations.