Superhydrophobic Research Articles

Oil-recovery performance of a superhydrophobic sponge-covered disc skimmer

Frequent oil spill accidents caused by transportation, storage and usage may lead to severe damage on aquatic and ecological environments. Effective methods for rapid oil recovery are urgently in demand. Polyvinyl chloride, hydrophobic nano-SiO2, expanded graphite were separately applied to polyurethane and melamine sponge to fabricate superhydrophobic sponge material. The selected superhydrophobic sponge was introduced to establish sponge - covered disc skimmer. Oil recovery tests of the device were conducted to determine the optimum parameters. The examined operating conditions encompassed sponge thickness, immersion depth, rotational speed, oil slick thickness, operation time. The results showed that the melamine sponge modified by both polyvinyl chloride and hydrophobic nano-SiO2 exhibits super-hydrophobicity with a water contact angle of 150.3°. The absorption capacity for diesel oil can reach 53.89 g/g. The absorption capacity can still achieve 90 % of its initial capacity even after 500 extrusion-absorption separation tests. The results indicate the superiority of the superhydrophobic sponge covered surface in oil recovery over the standard steel surface regardless of the operating conditions. The recovery rate of the device can still achieve 96.4 % of its initial capacity with 95 % efficiency even after 85 h operation. The results suggest the superhydrophobic sponge - covered disc skimmer may have great application perspectives in oil spill recovery.

Adjusting droplet adhesion of superhydrophobic coating via surface embedding of microparticles with mixed shapes

Designing intelligent superhydrophobic surfaces with versatile surface properties has garnered scholarly attention in field of heterogeneous catalysis, lab-on-chip, water harvesting, etc. However, the precise modulation of fluid adhesion on superhydrophobic surfaces, particularly when being applied as coatings, remains a challenge. Here we employ a “glue + powder” method for the fabrication of superhydrophobic surfaces with tunable droplet adhesion by embedding microparticles with mixed shapes. By adjusting the mixing ratio of rod-like and spherical particles, the sliding angle of superhydrophobic coating can be facilely controlled as well as the underwater bubble holding ability. During the dewetting process, the difference in the contact line lengths between micro-rod and micro-sphere contributes to the varying droplet adhesive force from 43.7 μN to 109.4 μN, which corresponds to the rolling-off angle change of a 10 μL droplet from 9.6° to 45.7°. Furthermore, by mixing fumed silica with branched structure, the lowest range of the rolling-off angle adjustment can be extended down to 0.5°, showing a precise and universal strategy for tuning the surface adhesion. On the basis of the meticulous manipulation of surface adhesion, controlling processes of single droplet and droplets accumulation can be fulfilled, with implications for enhancing the functionality of current superhydrophobic materials. Taking the advantage of the convenient and reliable fabrication method, a series of demonstration including manual droplet holders, multi-tiered droplet capturing interface, droplet sieving platforms, and gravity-driven droplet reactors has been realized. We envision that the precise control of droplet adhesion on superhydrophobic materials should further provides substantial opportunities for innovating fluid manipulation systems possessing heightened operability and multifunctionality.

Superdurable Full-Life Superhydrophobic Composite Block.

Superhydrophobic materials are attractive for industrial development but plagued by poor mechanical stability. Herein, a superdurable full-life superhydrophobic composite block is designed and fabricated by embedding near-zero contractive superhydrophobic silica aerogel into a rigid iron-nickel foam structured similarly to a regular dodecahedron. The synergistic protection afforded by these materials ensures superrobust mechanical stability for the composite block, which features a high compressive strength of up to ≈7.4MPa, and ultralow Taber abrasion of down to ≈0.567mm after withstanding 50000 cycles, and highly efficient water harvesting capability of up to ≈3114.3mg min-1 cm-2 at a supercooling degree of 40 K. This robust material system provides a novel strategy to design superhydrophobic materials capable of withstanding extreme conditions, including high temperature, humidity, pressure, and abrasion.

Pillar height regulated droplet impact dynamics on pillared superhydrophobic surfaces

Superhydrophobic surfaces that promote rapid droplet detachment have many significant engineering applications including self-cleaning, anti-icing, drag reduction. Adding macrotextures to superhydrophobic materials can markedly modify the dynamics of water impacting them, either by triggering a non-axisymmetric, center-assisted recoil or inducing pancake-like bouncing. However, the effect of pillar heights on superhydrophobic surfaces has received limited attention. Here, we have systematically investigated the role of the size ratio of pillar height-to-droplet radius (Q) on bouncing dynamics, including spreading, penetrating depth, contact time, bubble entrapment, impact pressure, and impact force, through numerical simulations. We show that droplet impact on superhydrophobic surfaces can generate two modes of bubble entrapment: one is an impinging cavity bubble, and the other is a recoiling cavity bubble, depending on Q. Furthermore, for low Weber number (We), droplet impacts may generate three peaks of impact force for superhydrophobic surfaces with high Q. For high We, only two peaks of impact force are generated during a droplet striking the superhydrophobic surface. However, the secondary peak in the impact force will weaken or may even disappear completely as Q increases, which was hitherto unknown. Interestingly, we also observe that despite lower impact force during droplet recoil compared to droplet impact, higher penetration depths are more easily achieved during the recoil stage. These findings shed light on the role of pillar heights in droplet impact dynamics, offering valuable insights for designing superhydrophobic surfaces.

Intelligent Devices Harnessing Underwater Superoleophobic and Underoil Superhydrophobic Quartz Sands for the Separation of Diverse Stratified and Emulsified Water-Oil Mixtures.

To achieve the green, sustainable, and controllable recovery of oil-water resources and to address the limited functionality of single superwet materials in oil-water separation, this study reports a multifunctional oil-water separation strategy by compositing the underwater superoleophobic and underoil superhydrophobic materials (HS). The underwater superoleophobic quartz sands with an oil contact angle of 152.68° were prepared by adjusting the particle size. This material demonstrated a water flux of 4688 L m-2 h-1 and a low-density oil and water mixture separation efficiency of 98.6%, which remained above 97.9% over 50 cycles. It was effective in separating oil-in-water emulsions with a separation efficiency of >99%. For HS, quartz sands were modified with dodecyltrimethoxysilane. The optimized HS-4 exhibited superhydrophobic properties with a water contact angle of 157.06°. It achieved an oil flux of 5775 L m-2 h-1 and a water and dichloromethane mixture separation efficiency of 98.4%. Additionally, they exhibited significant potential in the separation of water-in-oil emulsions. Furthermore, by placing the underwater superoleophobic and underoil superhydrophobic units at the bottom of the filter, we achieved cyclic separation of high-density oil and water mixtures, low-density oil and water mixtures, water-in-oil emulsions, and oil-in-water emulsions. The separation efficiency consistently exceeded 96.5% over 10 cycles. In addition, the oil-water separation mechanism of underwater oleophobic and underoil hydrophobic materials was demonstrated by the relative concentration distribution of water and oil with molecular dynamics simulations. This intelligent oil-water separation method marks a significant advancement in the sustainable separation of diverse oil-water mixtures.

Superhydrophobic, Highly Conductive, and Trilayered Fabric with Connected Carbon Nanotubes for Energy-Efficient Electrical Heating.

Current electrically heated fabrics provide heat in cold climates, suffer from abundant wasted radiant heat energy to the external environment, and are prone to damage by water. Thus, constructing energy-efficient and superhydrophobic conductive fabrics is in high demand. Therefore, we propose an effective and facile methodology to prepare a superhydrophobic, highly conductive, and trilayered fabric with a connected carbon nanotube (CNT) layer and a titanium dioxide (TiO2) nanoparticle heat-reflecting layer. We construct polyamide/fluorinated polyurethane (PA/FPU) nanofibrous membranes via first electrospinning, then performing blade-coating with the polyurethane (PU) solution with CNTs, and finally fabricating FPU/TiO2 nanoparticles via electrospraying. This strategy causes CNTs to be connected to form a conductive layer and enables TiO2 nanoparticles to be bound together to form a porous, heat-reflecting layer. As a consequence, the as-prepared membranes demonstrate high conductivity with an electrical conductivity of 63 S/m, exhibit rapid electric-heating capacity, and exhibit energy-efficient asymmetrical heating behavior, i.e., the heating temperature of the PA/FPU nanofibrous layer reaches more than 83 °C within 90 s at 24 V, while the heating temperature of the FPU/TiO2 layer only reaches 53 °C, as well as prominent superhydrophobicity with a water contact angle of 156°, indicating promising utility for the next generation of electrical heating textiles.

Rational design and application of superhydrophobic fluorine-free coating based on double-decker silsesquioxane for oil-water separation

A superhydrophobic coating of methoxysilane-functionalized double-decker silsesquioxane (M-DDSQ) on cotton fabric was synthesized using the dip-coating method. Characterizations using FT-IR, XPS, SEM, and AFM demonstrated that M-DDSQ-fabric has chemically covalently grafted M-DDSQ on the fabric surface and exhibits excellent chemical stability and antifouling properties compared to the pristine fabric. Interestingly, the novel fluorine-free fabric has a superhydrophobicity property with a water contact angle (WCA) of 150°, which efficiently and quickly separates oil from water. The maximum flux reaches 88,420 L m−2 h−1, and the separation efficiency is greater than 99 %. Furthermore, its outstanding superhydrophobic durability against tape-peeling, abrasion, and chemicals such as strong acidic and alkaline solutions is attributed to the strong chemical bonding between M-DDSQ and the fabric surface. This simple and efficient method enables the preparation of a durable superhydrophobic fluorine-free coating, which can be applied to synthesize other superhydrophobic materials for self-cleaning, especially for oil-water separation applications.

Facile Fabrication of Superhydrophobic and Superoleophilic Polyurethane Foil with Micropillar and Microporous Structures for Efficient Oil/Water Separation

Oil spill cleanup in water remains a critical challenge due to the harmful secondary pollution from conventional methods such as burning or chemical degradation. Herein, we present a facile method to fabricate a superhydrophobic and superoleophilic polyurethane (PU) foil for efficient and environmentally friendly oil/water separation. More specifically, micropillar arrays were embedded onto the foil surface through a nanoimprinting process. Microporous structures were generated at the foil cross-section by a supercritical carbon dioxide (CO2) saturation method. The dimensions of pillar and pore structures were optimized with the aim of boosting selective wetting (i.e., water repellency and oil attraction) properties. As a result, the developed PU foil shows an oil absorption efficiency nearly 4 times higher than a pristine reference. Moreover, the structured PU foil stably retains the absorbed oil for over a week, demonstrating an absorption capacity of nearly 400%, which is also much superior than the unstructured sample. Our concept of combining both topographical micropillars and cross-sectional micropores onto PU foil provides a novel approach for achieving efficient and environmental friendly oil/water separation.

SiC-armoured triple-layered superhydrophobic coating with super-robustness and anti-corrosion durability

Continuously enhancing the mechanical stability and durability of superhydrophobic corrosion-resistant materials is a great challenge for researchers. In this paper, we developed a SiC armoured triple-layered superhydrophobic coating with super-robustness on Q235 carbon steel substrates. The triple-layered coating was achieved by sequentially applying an epoxy (EP) resin adhesive layer, a SiC-armored skeleton structure, and a superhydrophobic F-Al2O3@EP layer. The resulting coating demonstrated outstanding non-wetting superhydrophobicity, featuring a static water contact angle (WCA) of 157.7 ± 0.5° and a sliding angle (SA) of 3.7 ± 0.6°. Moreover, the designed triple-layered superhydrophobic coating exhibits ultra-low interfacial adhesion force and demonstrates self-cleaning ability. Its mechanical stability was significantly heightened, enduring more than 2700 sandpaper abrasion cycles, 2200 tape-peeling cycles, and 3000 g sand impact resistance. Additionally, the coating displayed superior corrosion resistance with eight orders of magnitude enhanced charge transfer resistance (Rct), 590 mV positive shift corrosion potential (Ecorr), and six orders of magnitude lower corrosion current density (Icorr) in a 3.5 wt% NaCl solution. Impressively, the SiC armoured triple-layered superhydrophobic coating demonstrated prolonged marine anti-corrosion performance, enduring immersion in a 3.5 wt% NaCl solution for over 1200 h and exposure to the outdoor marine atmospheric environment for more than 3360 h. We believe the development of superhydrophobic materials with high stability and durability contributes to their widespread adoption and multifunctional applications.

An eco-friendly and facile method for oil-water separation using the bio-Zn oxide-based superhydrophobic membrane.

This manuscript presents a novel approach for developing an environmentally friendly and effective oil-water separation membrane. Achieving a superhydrophobic (SH) coating on textile fabric (TF) involved a two-step process. Initially, the surface roughness was enhanced by applying bio-zinc oxide (ZnO) nanoparticles obtained from Thymbra spicata L. Subsequently, the roughened surface was modified with stearic acid, a material known for its low surface energy. The bio-ZnO nanoparticles exhibit a circular morphology with an average size of 21 nm. The coating demonstrated remarkable mechanical stability, maintaining SH properties even after an abrasion length of 300 mm. Chemical stability studies revealed that the prepared membrane retained SH properties within a pH range of 5-11, which ensures robust performance. Absorption capacity measurements showcased different capacities for n-hexane (Hex), corn oil (C.O), and silicone oil (S.O), with consistent performance over 10 absorption-desorption cycles. High oil-water separation efficiencies were achieved for hexane, C.O, and S.O, emphasizing the coating's versatility. Flux rate measurements demonstrated that oil passed through the membrane efficiently, with the highest flux observed for Hex. The prepared SH membrane has superior mechanical and chemical stability and high separation efficiencies, which positions it as a promising candidate for diverse industrial applications.

Bilayer coating fabricated on aluminum alloy substrates with superamphiphobicity, corrosion resistance, self-cleaning, and delayed icing properties

To address the functional failure caused by low-surface-tension liquid wetting and adhesion in superhydrophobic materials, in this study, we constructed a bilayer coating with superamphiphobic properties using an epoxy (Ep) bonding layer and an organosilane-grafted attapulgite (OG-ATP) layer through spray-coating technique. The prepared superamphiphobic bilayer coating exhibited high contact angles (CAs) and low sliding angles (SAs) for cold water (25 °C), hot water (85 °C), glycerol, ethylene glycol, peanut oil, and even n-hexadecane (CA = 150.4 ± 0.3° and SA = 7 ± 2°) with surface tension of 27.5 mN m−1. Surface morphology and elemental analysis confirmed the coating's unique micro-nano hierarchical structure and low surface energy characteristics. Electrochemical impedance spectroscopy (EIS) results showed that the surface charge transfer resistance (Rct) and low-frequency modulus (|Z|0.01Hz) were enhanced by 6–7 orders of magnitude compared to the bare aluminum alloy substrate. The anti-corrosion performance remained stable even after 5 days of 3.5 wt% NaCl immersion. Additionally, icing experiments with water droplets at −10 °C and −15 °C revealed a significant delay in ice formation on the substrate protected by the bilayer coating. The development of this protective material, combining superamphiphobicity, self-cleaning, corrosion resistance, and anti-icing functions, will provide advanced technological reserves in areas such as marine, aviation, transportation, and manufacturing.

Electrochemically fast preparation of superhydrophobic copper mesh for high-efficiency oil spill adsorption and oil-water separation

Oily wastewater and marine oil spills are a massive environmental and human threat. Conventional oil spill treatment methods include adsorption by absorbent materials, dispersants or adsorbents, and in situ burning. Superhydrophobic materials, as a material that can achieve oil-water separation, have great potential for application in oil spill treatment. Research on superhydrophobic oil spill treatment mainly focuses on materials such as sponges and fabrics. Although these materials can effectively perform oil-water separation or oil spill adsorption, they also have the disadvantages of complicated preparation methods and high costs. Here, we present a miniature device for oil-water separation and oil spill collection and recovery. The superhydrophobic copper mesh box can be used on its own as an oil-water separation device or in combination with a commercial polyurethane sponge as a miniature oil-absorbing device. The robust copper mesh is prepared in two steps: anodizing and impregnation. The superhydrophobic copper mesh had a high oil separation flux (32,330 L m−2 h−1) and efficiency (97%), which remained high (28,560 L m−2 h−1) and efficient (95%) after 20 cycles of separation. The combined micro oil adsorption device can adsorb different oils and fats on the water surface, and it has good reusability with oil adsorption capacity and efficiency up to 15.28 g/g and 98% and still has good oil adsorption capacity (11.54 g/g) and efficiency (94.6%) after 20 cycles of adsorption. Therefore, the prepared micro oil-absorbing device has promising application prospects in oil-water separation, oil spill cleanup, etc. Environmental ImplicationThis study demonstrates a facile electrochemical approach to prepare a miniature device for high-efficiency oil-water separation and oil spill collection and recovery. The modified copper mesh's separation flux could reach 32,330 L m−2 h−1, showing great promise in oil-water separation and oil spill cleanup.

Synthesis of seawater-derived superhydrophobic calcium carbonate via CO2 mineralization by utilizing L-Arginine/L-Lysine oleate-based self-assembly structures

Superhydrophobic materials have been gaining popularity owing to their self-cleaning, anti-freezing, and anti-corrosion properties. This study presents an approach for the synthesis of superhydrophobic calcium carbonate via CO2 mineralization using carbon capture utilization (CCU) technology. By using biodegradable amino acids (L-arginine/L-lysine) and oleic acid, various biosurfactant self-assembly structures were formed as surface-modifying agents of calcium carbonate owing to the saponification and lyotropic phase transition. Moreover, calcium cations were recovered from salt-farm wastewater using pH-swing ion separation for sustainability and waste management. we presented various self-assembly structures depending on the ratio of amino acids to oleic acid, such as spherical micelles, liquid crystal nanoparticles, and vesicles for L-arginine oleate and spherical micelles, cylindrical micelles, and planar lamellar structures for L-lysine oleate. The synthesized calcium carbonates were 87.95 % purified scalenohedral calcite under micellar L-arginine oleate and 87.08 % purified spherical calcite under micellar L-lysine. Moreover, their surface areas were 28.85 m2/g for L-arginine and 13.46 m2/g for L-lysine. They were significantly improved and larger than that of commercial calcium carbonate (3.45 m2/g). In comparison, larger agglomerated calcite particles were produced under the other self-assembled structures. During mineralization, the amount of calcium oleate adsorbed on the surface of calcium carbonate played a crucial role in particle formation. Notably, superhydrophobic calcium carbonates were synthesized with a contact angle of 168.66° under spherical micelles of L-arginine oleate and 167.46° under spherical micelles of L-lysine oleate. The in-situ surface modification method utilizing biosurfactant self-assembled structures was expected to revitalize the carbon capture and utilization.

Superhydrophobic Materials for Self-cleaning Applications: A Review

Abstract: Since the discovery of the “lotus effect,” the superhydrophobic structure of the research is more and more profound. When the droplets fall on the surface, it will not occur as a wetting phenomenon. Making full use of this feature will achieve the self-cleaning effect of the object surface. In the dust filtration problem, it is possible to spray superhydrophobic materials on the surface of the equipment using superhydrophobic self-cleaning characteristics to change the filtering method and to improve the self-cleaning efficiency. This paper describes the methods of preparing superhydrophobic materials, self-cleaning methods, and the application of superhydrophobic materials in the field of self-cleaning. Based on the summary of patents and papers, this paper focuses on the filtration and self-cleaning effect of superhydrophobic materials on dust particles in humid environments. With a simple structure, high filtration efficiency, and long service life, the super sparse/hydrophilic hybrid mesh can work continuously without manual operation. It can effectively filter dust particles and improve air quality in humid environments. Coal powder condensation experiments in this paper proved that the application of superhydrophobic materials in the field of self-cleaning yielded significant results. When superhydrophobic materials are sprayed on copper-based filters, the hydrophilic line mixes with the hydrophobic region, greatly improving the self-cleaning efficiency.

Superhydrophobic finishing of cotton fabric via nonsolvent-induced phase separation of polystyrene–perfluoropolyether block copolymer

This paper reports synthesis of polystyrene–perfluoropolyether block copolymer@cotton fabric (PS–PFPE@CF) with a rough structure through nonsolvent-induced phase separation. The factors affecting the hydrophobicity of the coating, such as solvent quality, the molecular weight of the PS segments, and the volume ratio of tetrahydrofuran/1,3-di(trifluoromethyl)benzene (THF/DTFMB) and THF–MeOH, were all investigated, and the relation between the coating structure and hydrophobicity was also analyzed. In the THF–DTFMB system, PS–PFPE@CF (4 h, 80 mg/mL) appeared as a secondary structure with the superposition of small spheres on large spheres. For this structure, the water-contact angle reached 156.2° ± 0.5° and the sliding angle was 9.5° ± 1.5°. Furthermore, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and thermogravimetric analysis confirmed that PS–PFPE coated the cotton fabric. Finally, application tests were performed to assess the application prospects of PS–PFPE@CF. Oil-water separation, self-cleaning, and antifouling applications were studied, and the experimental results showed that the separation efficiency of the superhydrophobic fabric was nearly constant, from 99.4 % to 98.3 % after 10 oil-water separation tests. PS–PFPE@CF exhibited excellent self-cleaning properties and performed well in the sandpaper abrasion and tape peeling tests. This research thus used a degradable PFPE block copolymer to produce cotton fabrics with excellent hydrophobicity, self-cleaning, and wear resistance.

A flexible superhydrophobic thermoplastic polyurethane porous surface with good self-cleaning function prepared by supercritical CO2 foaming

Porous surfaces show great potential for superhydrophobic applications. Supercritical CO2 foaming is a green technology for preparing porous materials, but it is rarely used to prepare porous surfaces due to the non-porous skin caused by the escape of gas. In this study, a porous thermoplastic polyurethane (TPU) surface with dense cell and small cell spacing is prepared by employing bilayer TPU sheet to restrict the escape of gas from surfaces. The influence of the foaming pressure and temperature on the cells of the TPU surface is researched. Furthermore, bimodal cells are obtained by regulating the foaming process and the effect of cell structure on wettability is investigated. Subsequently, a flexible superhydrophobic material with low water-adhesion, mechanical stability, and self-cleaning properties is successfully prepared by modifying fluorinated silica particles on porous TPU surfaces.

Femtosecond laser structured black superhydrophobic cork for efficient solar-driven cleanup of crude oil

Marine oil spills have become a major global environmental challenge, yet there remains a lack of effective and environmentally friendly strategies for the remediation of water contaminated with high-viscosity oil. In this study, we introduce a superhydrophobic oleophilic material with photothermal properties for efficient absorption of viscous oil. Femtosecond laser treatment methodology is applied to cork (FSLA-cork), which exhibits not only superior hydrophobic and oleophilic properties but also the exceptional ability to be rapidly heated from ambient conditions to 58 °C in 10 s under 1.8 solar irradiation. Under solar irradiance, the FSLA-cork adsorbent functions synergistically by capillary absorption and centrifugal pumping. At one-sun intensity, an oil absorption rate of 4.02 g cm−2 within 200 s was observed. The high adsorption rates of FSLA-cork combined with the high availability of the raw material and its eco-friendly fabrication methods indicate that such methods and materials can be utilized for large-scale clean up of aqueous environments contaminated with high-viscosity oils.

Superhydrophobic stretchable conductive composite textile with weft-knitted structure for excellent electromagnetic interference shielding and Joule heating performance

Conductive composite textiles (CCTs) as multifunctional integrated platform provide an effective path for developing flexible electromagnetic interference (EMI) shielding composites. However, conventional CCTs suffer from EMI shielding performance failure or the loss of textile's intrinsic properties under large tensile strain. Hence, in this work, a stretchable EMI shielding CCT that retains the inherent attributes of textile is proposed via weft-knitting and in-situ chemical Ag deposition. The complete and continuous silver nanoparticles (AgNPs) conductive networks bring excellent conductivity (38560 S/m) and ultrahigh EMI shielding performance (80.1 dB) in unstretched state. When tensile strain is applied, the fibers are gradually straightened from flexural state within 40 % strain, and then begin to be stretched at bigger strains, which benefits from the weft-knitting structure. Therefore, the conductive networks on the fiber surfaces are well protected from damage in the initial 40 % strain range, resulting in a stable EMI shielding performance (51.7 dB) even after 1000 cycles of 100 % tensile strain. Crucially, the CCT preserves good air permeability, softness and lightness even though a series of modifications and tensile strains are applied. Other than the EMI shielding perforamnce, the excellent superhydrophobicity (the contact angle of 158°) imparts the textile with the capability to tackle complex environments easily. Moreover, the textile can readily be heated to 73.4 °C at a low voltage of 0.5 V, showing outstanding Joule heating performance. Even after a long period of heating (3600 s), the textile maintains superior thermal stability, indicating potential applications in wearable heaters. In brief, this multifunctional CCT has excellent comprehensive properties and is expected to further expand the applications of EMI shielding textiles.

A superhydrophobic e-fabric based on polydopamine template-assisted MXene/MWNTs with strain sensing, EMI shielding and electrothermal performance for health management

The development of superhydrophobic electronic fabric with multifunctionality, encompassing strain sensing, EMI (Electromagnetic interference) shielding, and electrical heating performances, is extremely challenging. These integrated functions enable the superhydrophobic electronic fabric to work effectively in diverse environments. A superhydrophobic electronic fabric is successfully developed by constructing synergetic conductive materials (MXene and MWNTs (Multi-walled carbon nanotubes)) on PDA (Polydopamine) layer adhered to fibers, followed by attaching SiO2 (Silicon dioxide) and PDMS (Polydimethylsiloxane) on conductive layer. MXene/MWNTs materials endow electronic fabric with a broad working range (up to100% strain), favorable GF (Gauge factor: 123.3), ultralow detection limit (0.2% strain), rapid response ability (60 ms), and satisfactory sensing stability over 5000 cycles. The construction of rough surface constructed by SiO2 and low surface energy provided by PDMS renders electronic fabric outstanding superhydrophobicity (WCA;Water contact angle:158°), enabling it to operate in complex environments (acid, base, and salt solutions), and detect subtle vibrations underwater. Besides, the superhydrophobic electronic fabric exhibits great EMI shielding effectiveness of 47 dB (8.2–12.4 GHz) and prominent electrothermal performance including highly electrothermal generation capability (95 °C at 8.0 V), rapid responsiveness for applied voltages, and satisfactory electrothermal stability. These commendable characteristics demonstrate that the superhydrophobic electronic fabric is promising for potential applications in EMI shielding, thermal management, and underwater movement mornitoring.

Role of coating techniques and low surface energy materials on long-term performance of superhydrophobic titanium

This study, for the first time, compares the performance of robust superhydrophobic (SHP) titanium (CP-Ti) surfaces developed by two different coating methods, (i) dip / immersion coating and (ii) spin coating, using two different low surface energy materials, (i) stearic acid and (ii) polydimethylsiloxane (PDMS). A facile two-step method for the fabrication of SHP Ti surface is followed, wherein the CP-Ti was first anodized and followed by the coating. The anodization of CP-Ti increased its surface roughness by developing a homogeneous coverage of randomly distributed micro-clusters, whose chemical composition was TiO2-xCly. Subsequent low surface energy organic coatings did not alter the surface morphology. The XPS analysis of stearic acid coated SHP Ti showed that the molecular structure of stearic acid is retained intact whereas the PDMS coated sample showed a partial modification of PDMS molecular structure with the presence of additional -[Si(O)2-O]- bonds apart from the inherent -[Si(CH3)2-O]- bonds. The water contact angle (WCA) and sliding angle (SA) values of SHP Ti were 170±5° and 6±2°, respectively. The SHP Ti showed excellent self-cleaning properties for both hydrophobic and hydrophilic contaminants. The adhesion test of the coatings showed the detachment of coating was within 5%. The coatings prepared by dip / immersion method retained their superhydrophobicity for an abrasion distance of about twice the length, (75±25 cm), due to a higher coating thickness, as compared to those obtained by the spin coating technique (40±20 cm). Further, the stearic acid-coated CP-Ti showed a better abrasion resistance while the stability of the PDMS-coated samples in different pH and Cl- environments was better. Nevertheless, both the stearic acid and PDMS-coated SHP CP-Ti samples showed excellent long-term stability against ambient atmosphere and UV exposure.