Surfaces with Sustainable Superhydrophobicity upon Mechanical Abrasion

Surfaces with sustainable superhydrophobicity have drawn much attention in recent years for improved durability in practical applications. In this study, hollow mesoporous silica nanoparticles (HMSNs) were prepared and used as reservoirs to load dodecyltrimethoxysilane (DDTMS). Then superhydrophobic surfaces were fabricated by spray coating HMSNs with DDTMS as particle stacking structure and polydimethylsiloxane (PDMS) as hydrophobic interconnection. The mechanical durability of the obtained superhydrophobic surface was evaluated by a cyclic sand abrasion. It was found that once the surface was mechanically damaged, new roughening structures made of the cavity of the HMSNs would expose and maintain suitable hierarchical roughness surrounded by PDMS and DDTMS, favoring sustainable superhydrphobicity of the coating. The surfaces could sustain superhydrophobicity even after 1000 cycles of sand abrasion. This facile strategy may pave the way to the development of robust superhydrophobic surfaces in practical applications

Surfaces with Sustainable Superhydrophobicity upon Mechanical Abrasion

Surfaces with sustainable superhydrophobicity have drawn much attention in recent years for improved durability in practical applications. In this study, hollow mesoporous silica nanoparticles (HMSNs) were prepared and used as reservoirs to load dodecyltrimethoxysilane (DDTMS). Then superhydrophobic surfaces were fabricated by spray coating HMSNs with DDTMS as particle stacking structure and polydimethylsiloxane (PDMS) as hydrophobic interconnection. The mechanical durability of the obtained superhydrophobic surface was evaluated by a cyclic sand abrasion. It was found that once the surface was mechanically damaged, new roughening structures made of the cavity of the HMSNs would expose and maintain suitable hierarchical roughness surrounded by PDMS and DDTMS, favoring sustainable superhydrphobicity of the coating. The surfaces could sustain superhydrophobicity even after 1000 cycles of sand abrasion. This facile strategy may pave the way to the development of robust superhydrophobic surfaces in practical applications

Flexible Superamphiphobic Film with a 3D Conductive Network for Wearable Strain Sensors in Humid Conditions

A three-dimensional (3D) conductive network with high sensitivity and a wide response range is applicable for wearable strain sensors. However, structural deformation of the 3D network under mechanical stimuli gives rise to mass pores, which are easily soaked by rain, sweat, oil, and so on, thus affecting the sensitivity of the sensors. Herein, a stretchable film with outstanding superhydrophobicity is proposed for reliable strain sensors based on a 3D conductive network. First, superconductive carbon black (SCB) nanoparticles are assembled on electrospun fibers of thermoplastic polyurethane (TPU) to form a TPU/SCB conductive film. Then, a dispersion of carbon nanotubes (CNTs) and fluorinated silica (F-SiO2) is sprayed on the TPU/SCB film to form a conductive TPU/SCB@CNTs/F-SiO2 composite film. After immersion of the composite film in a mixed solution of poly­(dimethylsiloxane) (PDMS) and perfluorodecyltrichlorosilane (PFDTS) and drying, a flexible conductive superamphiphobic film was obtained. When the film was used as a strain sensor, it showed superior sensitivity (12.05–60.42), a wide strain range (0–100%), a fast response time (75–100 ms), and good stability in stretching–relaxing cycles. Benefiting from the favorable superamphiphobicity, the obtained strain sensor could be effectively utilized to display stable electrical signals underwater and monitor human motions under dry/sweat exposure, showing significant potential in practical wearable sensors for stretchable, breathable, and reliable human behavior monitoring

Flexible Superamphiphobic Film with a 3D Conductive Network for Wearable Strain Sensors in Humid Conditions

A three-dimensional (3D) conductive network with high sensitivity and a wide response range is applicable for wearable strain sensors. However, structural deformation of the 3D network under mechanical stimuli gives rise to mass pores, which are easily soaked by rain, sweat, oil, and so on, thus affecting the sensitivity of the sensors. Herein, a stretchable film with outstanding superhydrophobicity is proposed for reliable strain sensors based on a 3D conductive network. First, superconductive carbon black (SCB) nanoparticles are assembled on electrospun fibers of thermoplastic polyurethane (TPU) to form a TPU/SCB conductive film. Then, a dispersion of carbon nanotubes (CNTs) and fluorinated silica (F-SiO2) is sprayed on the TPU/SCB film to form a conductive TPU/SCB@CNTs/F-SiO2 composite film. After immersion of the composite film in a mixed solution of poly­(dimethylsiloxane) (PDMS) and perfluorodecyltrichlorosilane (PFDTS) and drying, a flexible conductive superamphiphobic film was obtained. When the film was used as a strain sensor, it showed superior sensitivity (12.05–60.42), a wide strain range (0–100%), a fast response time (75–100 ms), and good stability in stretching–relaxing cycles. Benefiting from the favorable superamphiphobicity, the obtained strain sensor could be effectively utilized to display stable electrical signals underwater and monitor human motions under dry/sweat exposure, showing significant potential in practical wearable sensors for stretchable, breathable, and reliable human behavior monitoring

Flexible Superamphiphobic Film with a 3D Conductive Network for Wearable Strain Sensors in Humid Conditions

A three-dimensional (3D) conductive network with high sensitivity and a wide response range is applicable for wearable strain sensors. However, structural deformation of the 3D network under mechanical stimuli gives rise to mass pores, which are easily soaked by rain, sweat, oil, and so on, thus affecting the sensitivity of the sensors. Herein, a stretchable film with outstanding superhydrophobicity is proposed for reliable strain sensors based on a 3D conductive network. First, superconductive carbon black (SCB) nanoparticles are assembled on electrospun fibers of thermoplastic polyurethane (TPU) to form a TPU/SCB conductive film. Then, a dispersion of carbon nanotubes (CNTs) and fluorinated silica (F-SiO2) is sprayed on the TPU/SCB film to form a conductive TPU/SCB@CNTs/F-SiO2 composite film. After immersion of the composite film in a mixed solution of poly­(dimethylsiloxane) (PDMS) and perfluorodecyltrichlorosilane (PFDTS) and drying, a flexible conductive superamphiphobic film was obtained. When the film was used as a strain sensor, it showed superior sensitivity (12.05–60.42), a wide strain range (0–100%), a fast response time (75–100 ms), and good stability in stretching–relaxing cycles. Benefiting from the favorable superamphiphobicity, the obtained strain sensor could be effectively utilized to display stable electrical signals underwater and monitor human motions under dry/sweat exposure, showing significant potential in practical wearable sensors for stretchable, breathable, and reliable human behavior monitoring

Washable and Wear-Resistant Superhydrophobic Surfaces with Self-Cleaning Property by Chemical Etching of Fibers and Hydrophobization

Superhydrophobic poly­(ethylene terephthalate) (PET) textile surfaces with a self-cleaning property were fabricated by treating the microscale fibers with alkali followed by coating with polydimethylsiloxane (PDMS). Scanning electron microscopy analysis showed that alkali treatment etched the PET and resulted in nanoscale pits on the fiber surfaces, making the textiles have hierarchical structures. Coating of PDMS on the etched fibers affected little the roughening structures while lowered the surface energy of the fibers, thus making the textiles show slippery superhydrophobicity with a self-cleaning effect. Wettability tests showed that the superhydrophobic textiles were robust to acid/alkaline etching, UV irradiation, and long-time laundering. Importantly, the textiles maintained superhydrophobicity even when the textiles are ruptured by severe abrasion. Also colorful images could be imparted to the superhydrophobic textiles by a conventional transfer printing without affecting the superhydrophobicity

Scalable Superhydrophobic Flexible Nanofiber Film for Passive Daytime Radiative Cooling

Passive daytime radiative cooling technology can cool objects without any energy consumption. Although some progress has been made, there are still challenges in manufacturing low-cost, anticontaminant, and weathering-resistant radiative coolers for long-term cooling. Herein, a superhydrophobic flexible cooling radiator (SFCR) as a film is fabricated by a facile, inexpensive, and scalable electrospinning and electrospraying method. The SFCR film consists of poly­(vinylidene fluoride-co-hexafluoropropylene) fiber frameworks adhered to by numerous microaggregates from SiO2 nanoparticles. The SFCR film exhibited a strong solar reflectivity of 98.5% and an average emissivity of more than 95%. It also showed superior superhydrophobicity and wettability with a static water contact angle of 156° and sliding angle of 2.2°. The average temperature drop of the film was 11.6 °C compared to the air around the film under sunlight. Importantly, the self-cleaning effect of the SFCR film robustly protects its surface against outdoor contamination and is conducive to sustainable cooling. This SFCR film integrating radiative cooling with self-cleaning characteristics is promising for scalable production and can be utilized on buildings, vehicles, and other terrestrial objects

Scalable Superhydrophobic Flexible Nanofiber Film for Passive Daytime Radiative Cooling

Passive daytime radiative cooling technology can cool objects without any energy consumption. Although some progress has been made, there are still challenges in manufacturing low-cost, anticontaminant, and weathering-resistant radiative coolers for long-term cooling. Herein, a superhydrophobic flexible cooling radiator (SFCR) as a film is fabricated by a facile, inexpensive, and scalable electrospinning and electrospraying method. The SFCR film consists of poly­(vinylidene fluoride-co-hexafluoropropylene) fiber frameworks adhered to by numerous microaggregates from SiO2 nanoparticles. The SFCR film exhibited a strong solar reflectivity of 98.5% and an average emissivity of more than 95%. It also showed superior superhydrophobicity and wettability with a static water contact angle of 156° and sliding angle of 2.2°. The average temperature drop of the film was 11.6 °C compared to the air around the film under sunlight. Importantly, the self-cleaning effect of the SFCR film robustly protects its surface against outdoor contamination and is conducive to sustainable cooling. This SFCR film integrating radiative cooling with self-cleaning characteristics is promising for scalable production and can be utilized on buildings, vehicles, and other terrestrial objects

A Superhydrophobic Dual-Mode Film for Energy-Free Radiative Cooling and Solar Heating

Traditional electric cooling in summer and coal heating in winter consume a huge amount of energy and lead to a greenhouse effect. Herein, we developed an energy-free dual-mode superhydrophobic film, which consists of a white side with porous coating of styrene-ethylene-butylene-styrene/SiO2 for radiative cooling and a black side with nanocomposite coating of carbon nanotubes/polydimethylsiloxane for solar heating. In the cooling mode with the white side, the film achieved a high sunlight reflection of 94% and a strong long-wave infrared emission of 92% in the range of 8–13 μm to contribute to a temperature drop of ∼11 °C. In the heating mode with the black side, the film achieved a high solar absorption of 98% to induce heating to raise the air temperature beneath by ΔT of ∼35.6 °C. Importantly, both sides of the film are superhydrophobic with a contact angle over 165° and a sliding angle near 0°, showing typical self-cleaning effects, which defend the surfaces from outdoor contamination, thus conducive to long-term cooling and heating. This dual-mode film shows great potential in outdoor applications as coverings for both cooling in hot summer and heating in winter without an energy input

Durable and Scalable Superhydrophobic Colored Composite Coating for Subambient Daytime Radiative Cooling

Passive daytime radiative cooling without any energy input has attracted significant attention due to its ability to spontaneously radiate heat into cold outer spaces. However, the distinctive structure and optical properties made radiative cooling materials white in appearance, which limits their use in actual application. In this study, poly­(dimethylsiloxane) (PDMS), poly­(ethyl cyanoacrylate) (PECA), polystyrene (PS), and pigments that selectively absorb visible light with high emissivity were adopted to fabricate a colored superhydrophobic radiative cooling coating through spraying and nonsolvent-induced phase separation. The as-fabricated yellow, red, and green PS/PDMS/PECA composite coatings exhibited high solar reflectivities of 92.8, 89.8, and 86.6% with strong infrared emissivities of 95.4, 95.3, and 96.3%, respectively, which correspondingly realized a subambient temperature reduction of 5.3, 3.5, and 2.5 °C. The self-cleaning property of the coating caused by superhydrophobicity helps protect the coating from contamination, favoring a stable outdoor cooling performance. Additionally, the composite coating was resistant to different chemical immersions, ultraviolet (UV) irradiation, sand impact, water impact, and sandpaper abrasion, which might improve the applicability of the material and promote the cooling materials toward large-area production for practical application