Versatile Melanin-Like Coatings with Hierarchical Structure toward Personal Thermal Management, Anti-Icing/Deicing, and UV Protection

Tannic acid crosslinked chitosan/gelatin/SiO2 biopolymer film with superhydrophobic, antioxidant and UV resistance properties for prematuring fruit packaging

The environmental pollution caused by plastic films urgently requires the development of non-toxic, biodegradable, and renewable biopolymer films. However, the poor waterproof and UV resistance properties of biopolymer films have limited their application in fruit packaging. In this work, a novel tannic acid cross-linked chitosan/gelatin film with hydrophobic silica coating (CGTS) was prepared. Relying on the adhesion of tannic acid and gelatin to silica, the coating endows CGTS film with excellent superhydrophobic properties. Especially, the contact angle reaches a maximum value 152.6°. Meanwhile, tannic acid enhanced the mechanical strength (about 36.1 %) through the forming of hydrogen bonding and the network structure. The prepared CGTS films showed almost zero transmittance to ultraviolet light and exhibited excellent radical scavenging ability (∼76.5 %, DPPH). Hence, CGTS film is suitable as a novel multifunctional packaging material for the agriculture to protect premature fruits, or the food industry used in environments exposed to ultraviolet radiation and rainwater.

Smart and Sustainable Crop Protection: Design and Evaluation of a Novel α-Amylase-Responsive Nanopesticide for Effective Pest Control

In this study, an α-amylase-responsive controlled-release formulation was developed by capping polydopamine onto β-cyclodextrin-modified abamectin-loaded hollow mesoporous silica nanoparticles. The prepared Aba@HMS@CD@PDA were subjected to characterization using various analytical techniques. The findings revealed that Aba@HMS@CD@PDA, featuring a loading rate of 18.8 wt %, displayed noteworthy release behavior of abamectin in the presence of α-amylase. In comparison to abamectin EC, Aba@HMS@CD@PDA displayed a significantly foliar affinity and improved rainfastness on lotus leaves. The results of field trail demonstrated a significantly higher control efficacy against Spodoptera litura Fabricius compared to abamectin EC at all concentrations after 7, 14, and 21 days of spaying, showcasing the remarkable persistence of Aba@HMS@CD@PDA. These results underscore the potential of Aba@HMS@CD@PDA as a novel and persistently effective strategy for sustainable on-demand crop protection. The application of nanopesticides can enhance the effectiveness and efficiency of pesticide utilization, contributing to more sustainable agricultural practices.

Superhydrophobic Solar-to-Thermal Materials Toward Cutting-Edge Applications

Solar-to-thermal conversion is a direct and effective way to absorb sunlight for heat via the rational design and control of photothermal materials. However, when exposed to water-existed conditions, the conventional solar-to-thermal performance may experience severe degradation owing to the high specific heat capacity of water. To tackle with the challenge, the water-repellent function is introduced to construct superhydrophobic solar-to-thermal materials (SSTMs) for achieving stable heating, and even, for creating new application possibilities under water droplets, sweat, seawater, and ice environments. An in-depth review of cutting-edge research of SSTMs is given, focusing on synergetic functions, typical construction methods, and cutting-edge potentials based on water medium. Moreover, the current challenges and future prospects based on SSTMs are also carefully discussed.

Biomineralization-Inspired Copper Sulfide Decorated Aramid Textiles via In Situ Anchoring toward Versatile Wearable Thermal Management

Designing smart textiles for personal thermal management (PTM) is an effective strategy for thermoregulation and energy saving. However, the manufacture of versatile high-performance thermal management textiles for complex real-world environments remains a challenge due to the limitations of functional integration, material properties, and preparation procedures. In this study, an aramid fabric based on in situ anchored copper sulfide nanostructure is developed. The textile with excellent solar and Joule heating properties can effectively keep the body warm even at low energy inputs. Meanwhile, the reduced infrared emissivity of the textile decreases the thermal radiation losses and helps to maintain a constant body temperature. Impressively, the textile integrates superb electromagnetic shielding, near-complete UV protection properties, and ideal resistance to fire and bacteria. This work provides a simple strategy for fabricating multi-functional integrated wearable devices with flexibility and breathability, which is highly promising in versatile PTM applications.

An energy-free strategy to elevate anti-icing performance of superhydrophobic materials through interfacial airflow manipulation

Superhydrophobic surfaces demonstrate excellent anti-icing performance under static conditions. However, they show a marked decrease in icing time under real flight conditions. Here we develop an anti-icing strategy using ubiquitous wind field to improve the anti-icing efficiency of superhydrophobic surfaces during flight. We find that the icing mass on hierarchical superhydrophobic surface with a microstructure angle of 30° is at least 40% lower than that on the conventional superhydrophobic plate, which is attributed to the combined effects of microdroplet flow upwelling induced by interfacial airflow and microdroplet ejection driven by superhydrophobic characteristic. Meanwhile, the disordered arrangement of water molecules induced by the specific 30° angle also raises the energy barriers required for nucleation, resulting in an inhibition of the nucleation process. This strategy of microdroplet movement manipulation induced by interfacial airflow is expected to break through the anti-icing limitation of conventional superhydrophobic materials in service conditions and can further reduce the risk of icing on the aircraft surface.

Adaptive cooling strategy via human hair: High optothermal conversion efficiency of solar radiation into thermal dissipation

Natural species have developed complex nanostructures in a hierarchical pattern to control the absorption, reflection, or transmission of desired solar and infrared wavelengths. This bio-inspired structure is a promising method to manipulating solar energy and thermal management. In particular, human hair is used in this article to highlight the optothermal properties of bio-inspired structures. This study investigated how melanin, an effective solar absorber, and the structural morphology of aligned domains of keratin polymer chains, leading to a significant increase in solar path length, which effectively scatter and absorb solar radiation across the hair structure, as well as enhance thermal ramifications from solar absorption by fitting its radiative wavelength to atmospheric transmittance for high-yield radiative cooling with realistic human body thermal emission.

Ag Nanoparticles-Coated Shish-Kebab Superstructure Film for Wearable Heater

Passive and active wearable heaters have received widespread attention due to their efficient utilization of solar energy and all-weather heating capabilities, but the current challenges are their preparation processes being time-consuming and equipment expensive. Herein, a simple and facilitated preparation method for the multifunctional wearable heater was developed, which springs Ag nanoparticles on the shish-kebab superstructure film via deposited melanin-like polydopamine as the adhesive. The light absorption ability of the resultant wearable heater in the visible region can be significantly enhanced by the addition of polydopamine, realizing a highly efficient photothermal conversion ability. Accordingly, it can achieve rapid warming ability whether passive heating (up to 45 °C about 60 s at 100 mW/cm2) or active heating (up to 72 °C about 40 s at 0.6 V), compared to ordinary cotton fabric. In addition, it can realize a 6.3 °C temperature difference with Cotton, showing excellent heat preservation ability. This study demonstrates a simple and low-cost approach for the prepared shish-kebab superstructure-based wearable heaters.

Highly Efficient Photothermal Icephobic/de-Icing MOF-Based Micro and Nanostructured Surface

Photothermal materials have gained considerable attention in the field of anti-/de-icing due to its environmental friendliness and energy saving. However, it is always significantly challenging to obtain solar thermal materials with hierarchical structure and simultaneously demonstrate both the ultra-long icing delay ability and the superior photothermal de-icing ability. Here, a photothermal icephobic MOF-based micro and nanostructure surface (MOF-MNS) is presented, which consists of micron groove structure and fluorinated MOF nanowhiskers. The optimal MOF-M250 NS can achieve solar absorption of over 98% and produce a high temperature increment of 65.5 °C under 1-sun illumination. Such superior photothermal-conversion mechanism of MOF-M250 NS is elucidated in depth. In addition, the MOF-M250 NS generates an ultra-long icing delay time of ≈3960 s at -18 °C without solar illumination, achieving the longest delay time, which isn't reported before. Due to its excellent solar-to-heat conversation ability, accumulated ice and frost on MOF-M250 NS can be rapidly melted within 720 s under 1-sun illumination and it also holds a high de-icing rate of 5.8 kg m-2 h-1 . MOF-M250 NS possesses the versatility of mechanical robustness, chemical stability, and low temperature self-cleaning, which can synergistically reinforce the usage of icephobic surfaces in harsh conditions.

A Hierarchically Nanofibrous Self-Cleaning Textile for Efficient Personal Thermal Management in Severe Hot and Cold Environments

Climate change has recently caused more and more severe temperatures, inducing a growing demand for personal thermal management at outdoors. However, designing textiles that can achieve personal thermoregulation without energy consumption in severely hot and cold environments remains a huge challenge. Herein, a hierarchically nanofibrous (HNF) textile with improved thermal insulation and radiative thermal management functions is fabricated for efficient personal thermal management in severe temperatures. The textile consists of a radiative cooling layer, an intermediate thermal insulation layer, and a radiative heating layer, wherein the porous lignocellulose aerogel membrane (LCAM) as intermediate layer has low thermal conductivity (0.0366 W·m-1·K-1), ensuring less heat loss in cold weather and blocking external heat in hot weather. The introduction of polydimethylsiloxane (PDMS) increases the thermal emissivity (90.4%) of the radiative cooling layer in the atmospheric window and also endows it with a perfect self-cleaning performance. Solar absorptivity (80.1%) of the radiative heating layer is dramatically increased by adding only 0.05 wt% of carbon nanotubes (CNTs) into polyacrylonitrile. An outdoor test demonstrates that the HNF textile can achieve a temperature drop of 7.2 °C compared with white cotton in a hot environment and can be as high as 12.2 °C warmer than black cotton in a cold environment. In addition, the HNF textile possesses excellent moisture permeability, breathability, and directional perspiration performances, making it promising for personal thermal management in severely hot and cold environments.

Robust All-Waterborne Superhydrophobic Coating with Photothermal Deicing and Passive Anti-icing Properties

The compelling integration of superhydrophobic coatings with light-to-heat conversion capabilities has garnered substantial interest due to their dual functionality encompassing passive anti-icing and deicing attributes. However, the insufficient mechanical stability and the environmental and human health concerns stemming from the extensive use of organic solvents limit their practical application. In this study, an all-waterborne superhydrophobic photothermal coating (PCPAS) was prepared through the synergy of composite micro-nanoparticles derived from carbon nanotubes (CNT), polydopamine (PDA), and Ag particles with fluorine-containing polyacrylic emulsion (PFA). The PDA provided active sites for Ag+ reduction reaction and enhanced the interfacial interaction between CNT and Ag particles. The interfacial enhancement enabled the coating to maintain stable superhydrophobicity after 260 times sandpaper abrasion and 240 times tape peeling. Simultaneously, the composite micro-nanoparticle's light-to-heat conversion ability gave the coating excellent anti-icing/deicing capabilities. Under the condition of -20 °C, the freezing time of 30 μL of water droplets was extended to 392 s, and 2 × 2 × 2 cm ice cubes placed on the surface of the coating could completely melt after only 1142 s under simulated sunlight irradiation with a 1 kW/m2 intensity. In addition, the coating also had suitable self-cleaning properties and substrate applicability. The comprehensive attributes of this all-waterborne photothermal superhydrophobic coating render it a promising contender for anti-icing and deicing applications in challenging outdoor environments.

High-Efficient Anti-Icing/Deicing Method Based on Graphene Foams

Anti-icing/deicing has always been a focal issue in modern industries. A novel anti-icing/deicing material based on graphene foams (GF) is prepared in this paper, which integrates multiple functions, including electrothermal conversion, photothermal conversion, and superhydrophobicity. The GF sheet is used as a bottom layer bonded on the protected substrate, which is covered by a polymeric composite coating filled with TiN and SiO2 nanoparticles. Electric heating and light heating experiments are performed to study the anti-icing/deicing performances of such a GF-based material. It is found that, under the unique action of electric fields, a voltage of only 1 V is needed to increase the surface temperature from minus tens of degrees to the one above zero within 400 s, which is much lower than their previous counterparts of more than 10 V to achieve the same unfreezing effect. A slight increase of the applied voltage to 1.5 V can even result in a remarkable increase of the surface temperature from room temperature to more than 150 °C within 200 s, in contrast to existing electric heating techniques to attain peak temperatures of about 100 °C at the expense of tens of volts. Such performances enable the GF-based material to achieve an outstanding electrothermal energy conversion rate of more than 90%. Furthermore, with the help of sunlight illumination in addition to the electric power, not only can the critical voltage to prevent icing be reduced but also a much more rapid and adequate removal of ice or frost from the surface can be realized compared with the deicing/defrosting performance under either electric or light field alone. All of these results demonstrate the obvious advantages of the present method in superior energy utilization efficiency and universal applicability to dark and sunlight environments, which should be particularly useful for at-all-cost protection of key components in industrial equipment from icing.