Passive energy savings through the building envelope represent a critical strategy for reducing both energy consumption and carbon emissions. However, traditional technologies are limited by cumbersome control mechanisms and narrow adjustment scopes. To overcome these limitations, we propose a novel phase-change thermal diode with an enhanced unidirectional heat-transfer capacity. This thermal diode utilizes hydrophobic and hydrophilic materials, presenting dual benefits in material fabrication and structural applications. To verify the potential of this approach for building applications, the effect of different hydrophobic materials and vacuum on the performance of the thermal diode were compared experimentally. The optimally formulated material, which is readily manufacturable over large areas, demonstrated thermal rectification ranging from 8.72 to 23.62, thus offering an extensive adjustment range. For structural applications, the thermal diode could be combined with the building envelope to create a dynamic envelope for passive heat dissipation and insulation. Simulation studies confirmed that this novel dynamic adjustment method provides superior adjustment capabilities and achieves greater energy conservation than conventional dynamic methods. Specifically, cooling energy savings between 11.83% and 21.36% were attainable across various climate zones in China. This research fosters cross-innovation in the fields of buildings and materials, serving as a foundational reference for developing dynamic building envelopes.

Using superhydrophobic surfaces (SHSs) with the water-repellent Cassie-Baxter (CB) state is widely acknowledged as an effective approach for anti-icing performances. Nonetheless, the CB state is susceptible to diverse physical phenomena (e.g., vapor condensation, gas contraction, etc.) at low temperatures, resulting in the transition to the sticky Wenzel state and the loss of anti-icing capabilities. SHSs with various micronanostructures have been empirically examined for enhancing the CB stability; however, the energy barrier transits from the metastable CB state to the stable Wenzel state and thus the CB stability enhancement is currently not enough to guarantee a well and appliable anti-icing performance at low temperatures. Here, we proposed a dual-energy-barrier design strategy on superhydrophobic micronanostructures. Rather than the typical single energy barrier of the conventional CB-to-Wenzel transition, we introduced two CB states (i.e., CB I and CB II), where the state transition needed to go through CB I and CB II then to Wenzel state, thus significantly improving the entire CB stability. We applied ultrafast laser to fabricate this dual-energy-barrier micronanostructures, established a theoretical framework, and performed a series of experiments. The anti-icing performances were exhibited with long delay icing times (over 27,000 s) and low ice-adhesion strengths (0.9 kPa). The kinetic mechanism underpinning the enhanced CB anti-icing stability was elucidated and attributed to the preferential liquid pinning in the shallow closed structures, enabling the higher CB-Wenzel transition energy barrier to sustain the CB state. Comprehensive durability tests further corroborated the potentials of the designed dual-energy-barrier structures for anti-icing applications.

The melting of metals at high temperatures is common and important in many fields, e.g., metallurgy, refining, casting, welding, brazing, even newly developed batteries, and nuclear fusion, which is thus of great value in modern industrialization. However, the knowledge of the wetting behaviors of molten metals on various substrate surfaces remains insufficient, especially when the temperature is over 1000 °C and with microstructured metal substrate surfaces. Herein, we selected molten cerium (Ce) on a tantalum (Ta) substrate as an example and investigated in detail its wetting at temperatures up to 1000 °C by modulating the microstructures of the substrate surfaces via laser processing. We discovered that the wetting states of molten Ce on Ta surfaces at temperatures over 900 °C could be completely altered by modifying the laser-induced surface microstructures and the surface compositions. The molten Ce turned superlyophilic with its contact angle (CA) below 10° on the only laser-microstructured surfaces, while it exhibited lyophobicity with a CA of about 135° on the laser-microstructured plus oxidized ones, which demonstrated remarkably enhanced resistance against the melt with only tiny adhesion in this circumstance. In contrast, the CA of molten Ce on Ta substrate surfaces only changed from ∼25 to ∼95° after oxidization without laser microstructuring. We proved that modulating the substrate surface microstructures via laser together with oxidization was capable of efficiently controlling various molten metals' wetting behaviors even at very high temperatures. These findings not only enrich the understanding of molten metal high-temperature wettability but also enable a novel practical approach to control the wetting states for relevant applications.

Numerous state-of-the-art anti-icing surfaces have been developed to avoid undesired icing. However, they generally only work in the single static icing occasion. Under dynamic disturbances, the unstable interfacial states could fail easily, leading to the loss of icephobicity. The impalement of air interfaces on superhydrophobic surfaces and liquids captured by lubricant interfaces are two most known failure mechanisms. How to address these problems and develop a surface with adaptability to changeable harsh environments is of great challenge but of high value. Here we analyze the effects of structural sizes on surface resistance forces and slippery durability and propose a structural design method to balance their relationship. Adopting the optimized struc-tures, we fabricate an environmentally adapted slippery-superhydrophobic switchable surface, which reversibly switches interface states to maintain low adhesion in different environments. We demonstrate that the surfaces show excellent slippery anti-icing properties in static environments and overcome impalement issues. Even in extreme low-temperature environments, a photothermal-assisted droplet self-dislodging is realized. Confronting dynamic disturbances, the superhydrophobic interfaces are spontaneously activated with the broadened anti -water-impact ability (up to 200 kPa). A series of experiments confirm the long-term anti-icing, switchability and universality of our constructed surfaces, which could accelerate practical anti-icing applications in many related fields.

Superhydrophobic surface is one of the most promising materials for the prevention and elimination of ice in daily lives but its durability remains a tremendous problem. Inevitable deterioration on the low-free-energy coating caused by harsh environment restrains their potential applications. Icephobic polymers are more durable than mostly used fluorosilanes for their higher thickness and cohesive strength but difficult to be uniformly modified on rugged micro-nanostructures. In this study, a nanostructured tungsten carbide doped PDMS layer was uniformly covered on aluminum microcones via a hybrid fabrication process combining nanosecond and femtosecond laser ablations and a rotational homogenization process. The prepared superhydrophobic surfaces exhibited excellent water repellency and anti-icing properties in icing-deicing cycles, water flow impacting and freezing-melting cycles. Multiple mechanical/chemical damage tests were performed to test their durability comprehensively. In mechanical tests, the surfaces could withstand linear abrasion length of 240 cm under 5.2 kPa pressure, impacting sand amount of at least 80 g or tape peeling for at least 200 cycles. The chemical durability was elucidated in -40 to 200 degrees C cycles, 2-day ultraviolet exposure and immersion in different liquids. The proposed hybrid method to form homogenous, ductile and durable superhydrophobic coatings could yield a prospective candidate for applications in anti-fouling and anti-icing.

Based on geometrical characteristics, all surface microstructures are categorized into two types: closed-cell and open-cell structures. Closed-cell structures are well-known to have more stable and durable superhydrophobicity at room temperatures. However, in low-temperature environments where massive environmentally induced physical changes emerge, whether closed-cell surfaces can maintain good anti-icing performances has not yet been confirmed, and thus how to design optimal superhydrophobic anti-icing microstructures is rarely reported. Here, we apply an ultrafast laser to fabricate superhydrophobic surfaces with tunable patterned micro-nanostructures from a complete closed-cell to different ratios and to a complete open-cell. We discover that droplets on closed-cell structures completely degrade to the high-adhesion Wenzel state after icing and melting cycles while those on the open-cell structures well recover to the original Cassie-Baxter state. We propose an improved ideal gas model to clarify the mechanisms that the decreased air pocket pressure and the air dissolution on closed-cell structures induce easy impalement during icing and the difficult recovery during melting, paving the way for optimizing the anti-icing structure design. The optimized open-cell surfaces exhibit over 33 times lower ice adhesion strengths (1.4 kPa) and long-term icephobic durability (<20 kPa after 33 deicing cycles) owing to the increased air pocket pressure at low temperatures. Significant dewetting processes during condensation endow the open-cell structures with more remarkable high-humidity resistance and anti-frosting properties. Our study reveals the general design principle of superhydrophobic anti-icing structures, which might guide the design of superhydrophobic anti-icing surfaces in practical harsh environments.

Capillary-fed thin-film evaporation via micro/nanoscale structures has attracted increasing attention for its high evaporation flux and pumpless liquid replenishment. However, maximizing thin-film evaporation has been hindered by the intrinsic trade-off between the heat flux and liquid transport. Here, we designed and fabricated nanostructured micro-steam volcanoes on copper surfaces featuring triple-level super-wicking routes to overcome this trade-off and boost water evaporation. The triple-level super-wicking routes enable the continuous formation of a 3D thin film for highly efficient evaporation by continuous self-driven liquid replenishment and extending the thin-film region. The micro-steam volcanoes increased the surface area by 225%, improving the evaporation rate by 141%, with a rapid self-pumping water transport speed up to 80 mm s-1. A remarkable solar-driven water evaporation rate of 3.33 kg m-2 h-1 under one sun vertical incidence was achieved, which is among the highest reported values for metal-based evaporators. When attached to electric-heating plates, the evaporator realized an electrothermal evaporation rate of 12.13 kg m-2 h-1. Moreover, it can also be used for evaporative cooling with enhanced convective heat transfer, reaching a 36.2 °C temperature reduction on a heat source with a heat flux of 6 W cm-2. This study promises a general strategy for designing thin-film evaporators with high efficiencies, low costs, and multi-functional compatibilities.

Liquid fluidity is a most key prerequisite for a broad range of technologies, from energy, fluid machineries, microfluidic devices, water, and oil transportation to bio-deliveries. While from thermodynamics, the liquid fluidity gradually diminishes as temperature decreases until completely solidified below icing points. Here, self-driven droplet motions are discovered and demonstrated occurring in icing environments and accelerating with both moving distances and droplet volumes. The self-driven motions, including self-depinning and continuous wriggling, require no surface pre-preparation or energy input but are triggered by the overpressure spontaneously established during icing and then continuously accelerated by capillary pulling of frosts. Such self-driven motions are generic to a broad class of liquid types, volumes, and numbers on various micro-nanostructured surfaces and can be facilely manipulated by introducing pressure gradients spontaneously or externally. The discovery and control of self-driven motions below icing points can greatly broaden liquid-related applications in icing environments.

Thermal management systems are facing significant demand to dissipate increasing heat fluxes in time, however, heat transfer between solid surfaces is always obstructed due to the unperfect interfacial con-tact. Gallium-based room-temperature liquid metals (LM) are a type of emerging thermal interface ma-terials (TIMs) with superior thermal conductivity and deformability, efficiently enhancing the through -interface thermal transfer. However, the poor wettability of LMs with engineering materials (e.g., copper), which leads to non-negligible remaining gap/air at the interfaces, limits the further reduction of thermal interface resistance. Herein, a laser micropatterning approach is presented to significantly improve LM wetting behaviors with copper surfaces in the assistance of HCl solution, with the thermal interface re-sistance minimized to & SIM;0.37 mm2 & BULL;K/W which is four orders of magnitudes lower than that of two bare surfaces directly contacted and a quarter of that of bare surfaces with LM as TIM. Micropatterns featuring dense, shallow and open channels were designed and demonstrated to effectively expel trapped air while using a small amount of LM, which were both found necessary for reducing thermal interface resistance. We believe this study can lay a foundation for the further development and practical application of LMs based thermal management strategies.& COPY; 2023 Elsevier Ltd. All rights reserved.

Intelligent and adjustable building envelopes have the advantages of energy saving and comfort compared to traditional building envelopes and are an important direction for future development in the field of building engineering. However, complex regulation principle and redundant control methods limit their practical applications and large-scale developments. To overcome these limitations, in this study, through the innovative application of superhydrophobic and superhydrophilic materials, we first fabricated jumping-droplet thermal diodes with a maximum unidirectional heat transfer capacity of 18.24–26.62 times with large dynamic adjustment margins. Then, the performance-adjustable building envelope combined with the jumping-droplet thermal diode was designed. The simulation results showed that the building envelope can achieve 19.81% energy saving in mild climate zones, and the cooling energy saving potential in different climate zones ranges from 12.11 to 22.11%. The adjustment capacity of the new building envelope is 3.34 times that of the traditional dynamic building envelope. This study promotes innovations in the field of building and materials and their simultaneous application, which can provide some practical references for switchable heat transfer building envelopes.

Efficient thermal management has become a bottleneck for the further development of highly integrated and high-power optoelectronic devices. Vapor chambers (VCs) based on the passive liquid-vapor phase-change process have attracted increasing attention due to their extraordinary thermal management capabilities together with easy-to-assemble advantages. Nowadays, as optoelectronic devices continuously get more compact and miniaturized, there exists a great demand to develop high-performance ultra-thin VCs with overall thicknesses below 0.3 mm. However, the demand has been seldom reached by present VCs with either the layered or spaced configurations. Here, we demonstrated an extremely-thin VC (ETVC) with a three-region hybrid configuration fabricated via a facile laser micro/nano structuring approach, reaching a remarkable effective thermal conductivity of 12032 W/(m.K) with an overall thickness of only similar to 0.22 mm. Cross-arrayed micro-protrusions were fabricated on both the evaporation and condensation regions of the lower plate of the VC, connected by water/vapor passages composed of parallel micro-channels. The micro-channels were designed to make a layered-spaced hybrid configuration to accommodate the fast flow of both water and vapor. The surfaces of both the micro-protrusions and micro-channels were covered with plentiful finer features to render them excellent wicking performances. Such a laser microstructured three-region hybrid configuration enhances all main processes inside a VC (i.e., water evaporation, water condensation, and water/vapor transportation), boosting the self-driven circulation of water/vapor to efficiently homogenize temperature under different heat fluxes. We believe this work can lay a promising rationale for designing and fabricating highly-efficient highly-compact VCs for the increasing thermal management demand within high-end optoelectronics.

Controllable fabrication of surface micro/nano structures is the key to realizing surface functionalization for various applications. As a versatile approach, ultrafast laser ablation has been widely studied for surface micro/nano structuring. Increasing research efforts in this field have been devoted to gaining more control over the fabrication processes to meet the increasing need for creation of complex structures. In this paper, we focus on the in-situ deposition process following the plasma formation under ultrafast laser ablation. From an overview perspective, we firstly summarize the different roles that plasma plumes, from pulsed laser ablation of solids, play in different laser processing approaches. Then, the distinctive in-situ deposition process within surface micro/nano structuring is highlighted. Our experimental work demonstrated that the in-situ deposition during ultrafast laser surface structuring can be controlled as a localized micro-additive process to pile up secondary ordered structures, through which a unique kind of hierarchical structure with fort-like bodies sitting on top of micro cone arrays were fabricated as a showcase. The revealed laser-matter interaction mechanism can be inspiring for the development of new ultrafast laser fabrication approaches, adding a new dimension and more flexibility in controlling the fabrication of functional surface micro/nano structures.

With the burgeoning development of electronic devices with higher heat flux, thinner volume, lighter weight, and flexibility, heat pipes and vapor chambers are facing big challenges, especially in fabricating high-performance wicks within limited space. Microgrooves have gained increasing interest for the ability to be directly curved on the substrates, whereas the capillary performance enhancement hits a bottleneck. In this study, a chemical-free ultrathin aluminum wick with dual-scale microgrooves was fabricated via two-step laser texturing in 0.3 mm thick AA6061. The resultant surface, composed of main microgrooves and periodic sub-microgrooves in the ridges and valleys, demonstrated enhanced capillary performance via capillary rise rate experiments. The interaction of liquids in dual-scale microgrooves, that was the pumping effect and the flow resistance reducing effect, would be the main reason for the capillary performance enhancement. The ultrathin aluminum wick with dual-scale microgrooves exhibited a K/R-eff about 1.322 mu m with a shallow depth of about 100 mu m, increased by 11.3% compared with that of single-scale microgrooves due to the assistance of the sub-microgrooves. This wick kept the ability to transport liquid under bending angles of 90 and 135 degrees. Moreover, the wicking performance of different liquids decreased with the decrease of surface tension to viscosity ratio. The ultrathin aluminum wick with dual-scale microgrooves showed enhanced capillary performance, which was among the best with thickness less than 200 mu m to our knowledge. This work provides insight into the design of high-performance wicks within limited space and weight. (C) 2022 Elsevier Ltd. All rights reserved.

Ice formation and accretion have a severe negative impact, thus creating the tremendous demand for anti-icing/ deicing surfaces. Compared with other techniques, superhydrophobic surfaces possess unique advantages including extremely low affinity to water droplets and reduced ice adhesion strength, whereas their weak durability and failure in cold and moist environments restrict their practical applications. Therefore, photo -thermal superhydrophobic surfaces possessing high light absorptivity have been proposed, by which ice can be removed by harvesting solar energy as heat eco-friendly and efficiently. However, practical photothermal superhydrophobic surfaces with superior photothermal capability, anti-icing/deicing performance and high durability remain scarce. In this study, a durable cauliflower-like micro-nano structured superhydrophobic surface was produced by combining the ultrafast laser ablation and wet chemical reactions. The hierarchical structures, composed of microcones arrays, in-situ grown cauliflower-like structure and closely bonded PDMS layer, exhibited not only a high absorption rate of 97.3%, but also the high durability in both experimental and natural environment. The temperature raised 48.5 C under 1 sun illumination for 300 s in ambient conditions. The surface still kept superhydrophobic after several durability tests. The photothermal effect dramatically reduced the ice adhesion strength and deteriorations on the surface during its operation. Under the light intensity of 1 sun for 1 min each cycle, the ice adhesion strength maintained around 10 kPa stably over 40 icing-deicing cycles and the ice layer was melted under 2 min irradiation. Besides, in a three-month long outdoor experiment, the proposed superhydrophobic surface remained its efficient photothermal conversion capacity as well as high durability. Therefore, the cauliflower-like micro-nano structured superhydrophobic surface is one of the most promising methods for anti-icing/deicing applications due to the advantages of superior photothermal capability, long-term durability and adaptability.

The wicking phenomenon, including wicking and hemiwicking, has attracted increasing attention for its critical importance to a wide range of engineering applications, such as thermal management, water harvesting, fuel cells, microfluidics, and biosciences. There exists a more urgent demand for anisotropic wicking behaviors since an increasing number of advanced applications are significantly complex. For example, special-shaped vapor chambers and heating atomizers in some electronic cigarettes need liquid replenishing with various velocities in different directions. Here, we report two-dimensional anisotropic hemiwicking behaviors with elliptical shapes on laser structured prismatic microgrooves. The prismatic microgrooves were fabricated via one-step femtosecond laser direct writing, and the anisotropic hemiwicking behaviors were observed when utilizing glycerol, glycol, and water as the test liquid. Specifically, the ratios of horizontal wicking distance in directions along short and long axes were tan 0°, tan 15°, tan 30°, and tan 45° for samples with cross-angles of 0°, 30°, 60°, and 90°, respectively. The vertical water wicking front displayed corresponding angles under the guidance of laser structured prismatic microgrooves. Theoretical analysis shows that the wicking distance is mainly dependent on the cross-angle θ and surface roughness, in which the wicking distance is proportional to cos(θ/2). Driven by the capillary pressure forming in the narrow microgrooves, the liquid initially filled the valleys of microgrooves and then surrounded and covered the prismatic ridges with laser-induced nanoparticles. The abundant nanoparticles increased the surface roughness, leading to the enhancement of wicking performance, which was further evidenced by the larger wicking speed of the sample with more nanoparticles. The mechanism of anisotropic hemiwicking behaviors revealed in this work paves the way for wicking control, and the proposed prismatic microgrooved surfaces with two-dimensional anisotropic hemiwicking performance and superhydrophilicity could serve in a broad range of applications, especially for the advanced thermal management with specific heat load configurations.

Surface-enhanced Raman Scattering (SERS) possesses unique advantages including convenient operation, label free, simple pretreatment process, non-destructive inspection and reliable test results. Aimed at practical applications, the SERS substrates need comprehensive properties in low-cost, rapid detection, high sensitivity, uniformity, stability and universality. Facile fabrication such as laser ablation and high-throughput detection can greatly reduce the cost and improve the detection efficiency. Meanwhile, superhydrophobic surfaces can increase the sensitivity and uniformity via evaporation enrichment. Herein, we report a patterned hydrophobic/superhydrophobic SERS platform, achieving the detection of 10-14mol/L Rhodamine 6G with an effect factor up to 2.1 x 1011 and high-throughput detection for at least nine different samples simultaneously. Notably, considering the abuse of hazardous fish drugs, we further apply this platform to detect crystal violet, malachite green, methylene blue, their mixtures and the crystal violet residue on contaminated fish scales. These results demonstrate that this SERS platform can not only maintain its relatively high sensitivity but also perform excellent distinguishing ability, offering valuable information on the application fields including food safety evaluation.

Anti-icing superhydrophobic surfaces have been a key research topic due to their potential application value in aviation, telecommunication, energy, etc. However, superhydrophobicity is easily lost during icing & melting cycles, where the water-repellent Cassie-Baxter state turns to the sticky Wenzel state. The reversible transition during icing & melting cycle without external assistance is challenging but vital for reliable anti-icing superhydrophobic performance, such a topic has rarely been reported. Here we demonstrate a spontaneous Wenzel to Cassie-Baxter dewetting transition during icing & melting cycle on well-designed superhydrophobic surfaces. Bubbles in ice droplets rapidly impact the micro-nano valleys under Marangoni force, prompting the continuous recovery of air pockets during melting processes. We establish models to confirm the bubbles movement broadens the dewetting conditions greatly and present three criteria for the dewetting transitions. This research deepens the understanding of wettability theory and extends the design of anti-icing superhydrophobic surfaces.

Superhydrophobic surfaces often lose the easy-removal ability of liquids during icing & melting cycles due to the impalement phenomena of air pockets. Especially for the most common mixed liquids in normal life, their difficult-removals after icing and melting have brought colossal troubles in the fields of aviation, energy, biomedicine, etc. Here we adopt the ultrafast laser to fabricate the optimal micro-nanostructured surfaces, realizing excellent superomniphobicity for seven environmental-related liquids. It is demonstrated that different droplets on the surfaces recover well to the original Cassie-Baxter state after melting, and can be removed easily at low tilted angles. The ice adhesion strengths of the seven liquids as low as 5 kPa and the micro-nanostructure durability ensure the long-term easy-removal after icing. Compared with the ice adhesion strength of untreated surfaces (264.4 ± 17.6 kPa), those of our designed surfaces have decreased by over 50 times. Icing and melting processes are investigated to reveal the easy-removal mechanisms that specifically distributed solutes and bubbles after icing impact downwards significantly to accelerate the recovery of the Cassie—Baxter state during melting. A series of environmental-related durability experiments including continuous icing & melting cycles, long-term salt spray, and high-pressure water jet impact further demonstrate the surfaces promising for real applications.

Gallium-based room-temperature liquid metal (LM) is a promising emerging functional material in e-skin, soft robots and thermal management systems for its fluidity, conductivity and nontoxicity. However, the intricate wettability of the LM with various surfaces impedes its further development. Knowledge on the gallium-based LM wetting properties especially with structured metal surfaces is relatively insufficient. Herein, wetting behavior of eutectic gallium-indium (EGaIn) on various micro-structured metal surfaces processed by nano-second laser ablation method is systematically studied. Increasing surface roughness, synergized with a high oxygen content, significantly strengthens the LM resistance. Micro-patterns composed of small, discontinuous facets exhibit better EGaIn repellence. Relative humidity (RH) is substantiated to influence the LM wetting behavior as well. Metal surfaces with excellent superlyophobicity (the contact angle> 160 degrees, the adhesion force< 10 mu N) are obtained. The LM repellence stability and anti-corrosion properties of the optimized treated metal surfaces are proved via the droplet impacting experiment and the corrosion test. These findings improve the understanding of gallium-based LM wetting behavior on structured metal surfaces, and the obtained LM-repellent metal surfaces will reduce undesired adhesion, blockage or LM corrosion during device preparation and long-term applications, which will facilitate its potential use.

A low-temperature, open-air plasma process to deposit amorphous SnOx thin films as an electron-transport layer in a planar-heterojunction n-i-p perovskite solar cell is reported. Open-air plasma processing is a scalable, low capital expenditure technique capable of manufacturing-scale production without enclosures or vacuum pumps. The technique provides flexibility to tune SnOx film composition and properties by adjusting several easily accessible processing parameters. In this study, we demonstrate large area SnOx thin film deposition on substrates up to 100 cm2. The SnOx films are deposited using monobutyltin trichloride as the chemical precursor and formed without any post-annealing, which has the potential for lowering costs as an in-line process. The film exhibits low surface roughness, excellent optical transmission of greater than 90 % across the visible regime, and low electrical resistivity of 13.3 omega*m, which is multiple orders of magnitude lower than previously reported values of amorphous SnO2 thin films. The film is then incorporated into a planar perovskite solar cell with a power conversion efficiency of 11.8 %. These factors suggest that open-air plasma-deposited SnOx thin films can potentially be compatible with low-cost and large-scale fabrication of organohalide lead perovskite solar cells and modules.