Self-Driven Droplet Motions Below their Icing Points.

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.

1000 °C High-Temperature Wetting Behaviors of Molten Metals on Laser-Microstructured Metal Surfaces.

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.

Ultrafast Laser Enabling Hierarchical Structures for Versatile Superhydrophobicity with Enhanced Cassie-Baxter Stability and Durability.

The controllable and facile fabrication of surface micro/nanostructures with the required dimensions and morphologies is the key to achieving surface superhydrophobicity. With the advantages of being a noncontact, maskless, programmable, and one-step process, ultrafast laser irradiation is a very flexible and adaptive technique for fabricating various microscale, nanoscale, and micro/nanomultiscale surface structures on diverse solids, thus realizing superhydrophobicity on their surfaces. In this feature article, a comprehensive review of our recent research advances on versatile superhydrophobic surfaces enabled by ultrafast lasers is presented from the perspectives of materials, methodologies, and functionalization. The realization of superhydrophobicity and even superamphiphobicity on varied solid surfaces through ultrafast laser treatment and the underlying mechanisms for the wettability transition of ultrafast-laser-processed surfaces from superhydrophilicity to superhydrophobicity will be discussed. For the sake of practical applications, the ultrafast-laser-based strategies for the large-scale and cost-effective fabrication of superhydrophobic surface micro/nanostructures will be introduced. A special focus will be devoted to the enhancement of structural durability and the Cassie-Baxter stability of ultrafast-laser-enabled superhydrophobic surfaces. Beyond that, the achievement of integrated surface functions including remarkable wetting functions such as the directional collection of water droplets and superhydrophobic surfaces simultaneously with unique optical properties will also be presented.

Cassie-State Stability of Metallic Superhydrophobic Surfaces with Various Micro/Nanostructures Produced by a Femtosecond Laser.

The Cassie-state stability plays a vital role in the applications of metallic superhydrophobic surfaces. Although a large number of papers have reported the superhydrophobic performance of various surface micro/nanostructures, the knowledge of which kind of micro/nanostructure contributes significantly to the Cassie-state stability especially under low temperature and pressure is still very limited. In this article, we fabricated six kinds of typical micro/nanostructures with different topography features on metal surfaces by a femtosecond laser, and these surfaces were modified by fluoroalkylsilane to generate superhydrophobicity. We then systematically studied the Cassie-state stability of these surfaces by means of condensation and evaporation experiments. The results show that some superhydrophobic surfaces, even with high contact angles and low sliding angles under normal conditions, are unstable under low temperature or external pressure. The Cassie state readily transits to a metastable state or even a Wenzel state under these conditions, which deteriorates their superhydrophobicity. Among the six micro/nanostructures, the densely distributed nanoscale structure is important for a stable Cassie state, and the closely packed micrometer-scale structure can further improve the stability. The dependence of the Cassie-state stability on the fabricated micro/nanostructures and the laser-processing parameters is also discussed. This article clarifies optimized micro/nanostructures for stable and thus more practical metallic superhydrophobic surfaces.

Broadband High-Performance Infrared Antireflection Nanowires Facilely Grown on Ultrafast Laser Structured Cu Surface.

Infrared antireflection is an essential issue in many fields such as thermal imaging, sensors, thermoelectrics, and stealth. However, a limited antireflection capability, narrow effective band, and complexity as well as high cost in implementation represent the main unconquered problems, especially on metal surfaces. By introducing precursor micro/nano structures via ultrafast laser beforehand, we present a novel approach for facile and uniform growth of high-quality oxide semiconductor nanowires on a Cu surface via thermal oxidation. Through the enhanced optical phonon dissipation of the nanowires, assisted by light trapping in the micro structures, ultralow total reflectance of 0.6% is achieved at the infrared wavelength around 17 µm and keeps steadily below 3% over a broad band of 14-18 µm. The precursor structures and the nanowires can be flexibly tuned by controlling the laser processing procedure to achieve desired antireflection performance. The presented approach possesses the advantages of material simplicity, structure reconfigurability, and cost-effectiveness for mass production. It opens a new path to realize unique functions by integrating semiconductor nanowires onto metal surface structures.

Dual-Energy-Barrier Stable Superhydrophobic Structures for Long Icing Delay.

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.

Rapid fabrication of surface micro/nano structures with enhanced broadband absorption on Cu by picosecond laser.

A surface micro/nano structuring technique was demonstrated by utilizing a picosecond laser beam to rapidly modify the optical property of copper surfaces with a scanning speed up to tens of millimeters per second. Three kinds of surface micro/nanostructures corresponding to three levels of reflectance were produced which are obviously different from those induced by a femtosecond or nanosecond laser. Specifically, a porous coral-like structure results in over 97% absorptivity in the visible spectral region and over 90% absorptivity in average in the UV, visible, and NIR regions (250 - 2500 nm). Potential applications may include solar energy absorbers, thermal radiation sources, and radiative heat transfer devices.

Localized in-situ deposition: a new dimension to control in fabricating surface micro/nano structures via ultrafast laser ablation.

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.

Crack-Initiated Durable Low-Adhesion Trilayer Icephobic Surfaces with Microcone-Array Anchored Porous Sponges and Polydimethylsiloxane Cover.

Reducing unfavorable ice accretion on surfaces exposed in cold environment requires effective passive anti-icing/deicing techniques. Icephobic surfaces are widely applied on various infrastructures due to their low ice adhesion strength and flexibility, whereas their poor mechanical durability, common liquid infusion, weak resistance to contamination, and low bonding strength to substrates are the major remaining challenges. According to the fracture mechanics of ice layer, initiating cracks at the ice-solid interfaces via the proper design of internal structures of icephobic materials is a promising way to icephobicity. Herein, a crack initiating icephobic surface with porous PDMS sponges sandwiched between a protective, dense PDMS layer and a textured metal microstructure was proposed and fabricated. The combination of high- and low- stiffness PDMS layers anchored by the structured metal surface give the sandwich-like structure excellent icephobicity with both high durability and low ice adhesion (5.3 kPa in the icing-deicing cycles). The porosity and the elastic modulus of the PDMS sponges and the periodicity of the metal surface structures can both be tailored to realize enhanced icephobicity. The sandwich-like icephobic surface remained insignificantly changed under solid particle impacting and the durability characterized via linear abrasion tests was elevated compared with PDMS coating on flat metal surfaces. Additionally, the trilayer icephobic surface possesses durability, low ice adhesion strength, and improved resistance to contamination and is applicable on various surfaces.

Passive Anti-Icing Performances of the Same Superhydrophobic Surfaces under Static Freezing, Dynamic Supercooled-Droplet Impinging, and Icing Wind Tunnel Tests.

Overcoming ice accretion on external aircraft wing surfaces plays a crucial role in aviation, and developing environmentally friendly passive anti-icing surfaces is considered to be a promising strategy. Superhydrophobic surfaces (SHSs) have attracted increasing attention due to their potential advantages of keeping the airframe dry without causing additional aerodynamic losses. However, the passive anti-icing performances of SHSs reported to date varied a lot under different icing test conditions. Therefore, a systematic investigation is necessary to elucidate the icing conditions where SHSs can remain effective and pave the way for SHSs toward practical anti-icing applications. Herein, we designed and fabricated a typical type of SHS featuring dual-scale hierarchical structures with arrayed micromountains (with both spacings and heights of tens of micrometers) covered by single-scale sandy-corrugation-like periodic structures (with both spacings and heights of only several micrometers) (termed SS1). Its anti-icing performances under three representative icing conditions, including static water freezing, dynamic supercooled-droplet impinging, and icing wind tunnel conditions, were comparatively investigated. The SS1 SHS maintained a lower static ice-adhesion strength (<60 kPa even after 50 deicing cycles at temperatures as low as -25 °C), which was attributed to a cumulative cracking effect facilitating the ice detachment. Within the laboratory dynamic icing tests, the SS1 SHSs with micromountain heights of 20-30 µm performed optimally in the antiadhesion of supercooled droplets (at an impinging velocity of 3.4 m/s and temperatures of -5 to -25 °C). In spite of the significant anti-icing performances of the SS1 SHSs in both static and dynamic laboratory tests, they could hardly sustain reliable passive anti-icing performances in harsher icing wind tunnel tests with supercooled droplets impinging their surfaces at velocities of up to 50 m/s at a temperature of -5 °C for 10 min. This study can inspire the development of improved SHSs for achieving satisfactory anti-icing performances in real-aviation conditions.

Superhydrophobic microstructures for better anti-icing performances: open-cell or closed-cell?

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.

Boosting water evaporation via continuous formation of a 3D thin film through triple-level super-wicking routes.

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.

Large-scale assembly of isotropic nanofiber aerogels based on columnar-equiaxed crystal transition.

Ice-templating technology holds great potential to construct industrial porous materials from nanometers to the macroscopic scale for tailoring thermal, electronic, or acoustic transport. Herein, we describe a general ice-templating technology through freezing the material on a rotating cryogenic drum surface, crushing it, and then re-casting the nanofiber slurry. Through decoupling the ice nucleation and growth processes, we achieved the columnar-equiaxed crystal transition in the freezing procedure. The highly random stacking and integrating of equiaxed ice crystals can organize nanofibers into thousands of repeating microscale units with a tortuous channel topology. Owing to the spatially well-defined isotropic structure, the obtained Al2O3·SiO2 nanofiber aerogels exhibit ultralow thermal conductivity, superelasticity, good damage tolerance, and fatigue resistance. These features, together with their natural stability up to 1200 °C, make them highly robust for thermal insulation under extreme thermomechanical environments. Cascading thermal runaway propagation in a high-capacity lithium-ion battery module consisting of LiNi0.8Co0.1Mn0.1O2 cathode, with ultrahigh thermal shock power of 215 kW, can be completely prevented by a thin nanofiber aerogel layer. These findings not only establish a general production route for nanomaterial assemblies that is conventionally challenging, but also demonstrate a high-energy-density battery module configuration with a high safety standard that is critical for practical applications.

An integrative bioinspired venation network with ultra-contrasting wettability for large-scale strongly self-driven and efficient water collection.

Collection of water from the atmosphere is a potential route to alleviate the global water shortage. However, it is still difficult to find a strategy to collect sufficient water on a large surface and transport it all off the surface without additional energy input. Inspired by redbud leaves, herein, we proposed a new water-collecting configuration. This configuration utilizes an ultra-contrasting wettability venation network with hierarchical micro-nano structures as the skeleton and integrates the strategies evolved by cacti and beetles. This venation network was fabricated by the technology based on ultra-fast lasers. We achieved a near-unity efficiency in collecting and centralizing the condensed water on the entire surface with a large area. Remarkable water collection and centralization capability were obtained. The venation networks manifested the notable enhancements of ∼166%, ∼352% and ∼644% in water collection efficiency when compared with conventional superhydrophobic surfaces at the tilt angles of 90°, 60° and 30°, respectively. This configuration can work continuously at all tilt angles, even against gravity at a negative tilt angle of 90°. In addition, the venation network can maintain excellent water collecting capability even under very arid conditions. The principle and fabrication technology of this venation network make it possible to scale up a practical network device for mass water collection and may be useful for water desalination, heat transfer, microfluidics, lab-on-a-chip, distillation and many other applications.

General Strategy toward Dual-Scale-Controlled Metallic Micro-Nano Hybrid Structures with Ultralow Reflectance.

Functional metal surfaces with minimum optical reflection over a broadband spectrum have essential importance for optical and optoelectronic devices. However, the intrinsically large optical impedance mismatch between metals and the free space causes a huge obstacle in achieving such a purpose. We propose and experimentally demonstrate a general pulse injection controlled ultrafast laser direct writing strategy for fabricating highly effective antireflection structures on metal surfaces. The presented strategy can implement separate and flexible modifications on both microscale frame structures and nanoscale particles, a benefit from which is that optimized geometrical light trapping and enhanced effective medium effect reducing the surface reflection can be simultaneously achieved within one hybrid structure. Thus, comprehensively improved antireflection performances can be realized. Hybrid structures with substantial nanoparticles hierarchically attached on regularly arrayed microcones are generally constructed on different metal surfaces, achieving highly efficient light absorption over ultraviolet to near-infrared broadband spectrum regions. Reflectance minimums of 1.4%, 0.29%, and 2.5% are reached on Cu, Ti, and W surfaces, respectively. The presented strategy is simple in process, adaptable for different kinds of metals, reproduceable in dual-scale structural features, and feasible for large-area production. All these advantages make the strategy as well as the prepared antireflection structures excellent candidates for practical applications.

Large-Scale Tunable 3D Self-Supporting WO3 Micro-Nano Architectures as Direct Photoanodes for Efficient Photoelectrochemical Water Splitting.

Hydrogen production from water based on photoelectrochemical (PEC) reactions is feasible to solve the urgent energy crisis. Herein, hierarchical 3D self-supporting WO3 micro-nano architectures in situ grown on W plates are successfully fabricated via ultrafast laser processing hybrid with thermal oxidation. Owing to the large surface area and efficient interface charge transfer, the W plate with hierarchical porous WO3 nanoparticle aggregates has been directly employed as the photoanode for excellent PEC performance, which exhibits a high photocurrent density of 1.2 mA cm-2 at 1.0 V vs Ag/AgCl (1.23 V vs RHE) under AM 1.5 G illumination and reveals excellent structural stability during long-term PEC water splitting reactions. The nanoscale and microscale features can be facilely tuned by controlling the laser processing parameters and the thermal oxidation conditions to achieve improved PEC activity. The presented hybrid method is simple, cost-effective, and controllable for large-scale fabrication, which should provide a new and general route that how the properties of conventional metal oxides can be improved via hierarchical 3D micro-nano configurations.

Large-scale cauliflower-shaped hierarchical copper nanostructures for efficient photothermal conversion.

Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ∼1 kW m(-2). The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area.

Robust and Stable Transparent Superhydrophobic Polydimethylsiloxane Films by Duplicating via a Femtosecond Laser-Ablated Template.

Realizing superhydrophobicity, high transparency on polydimethylsiloxane (PDMS) surface enlarges its application fields. We applied a femtosecond laser to fabricate well-designed structures combining microgrooves with microholes array on mirror finished stainless steel to form a template. Then liquid PDMS was charged for the duplicating process to introduce a particular structure composed of a microwalls array with a certain distance between each other and a microprotrusion positioned at the center of a plate surrounded by microwalls. The parameters such as the side length of microwalls and the height of a microcone were optimized to achieve required superhydrophobicity at the same time as high-transparency properties. The PDMS surfaces show superhydrophobicity with a static contact angle of up to 154.5 ± 1.7° and sliding angle lower to 6 ± 0.5°, also with a transparency over 91%, a loss less than 1% compared with plat PDMS by the measured light wavelength in the visible light scale. The friction robust over 100 cycles by sandpaper, strong light stability by 8 times density treatment, and thermal stability up to 325 °C of superhydrophobic PDMS surface was investigated. We report here a convenient and efficient duplicating method, being capable to form a transparent PDMS surface with superhydrophobicity in mass production, which shows extensive application potentials.

Superhydrophilicity to superhydrophobicity transition of picosecond laser microstructured aluminum in ambient air.

Studies regarding the wettability transition of micro- and nano-structured metal surfaces over time are frequently reported, but there seems to be no generally accepted theory that explains this phenomenon. In this paper, we aim to clarify the mechanism underlying the transition of picosecond laser microstructured aluminum surfaces from a superhydrophilic nature to a superhydrophobic one under ambient conditions. The aluminum surface studied exhibited superhydrophilicity immediately after being irradiated by a picosecond laser. However, the contact angles on the surface increased over time, eventually becoming large enough to classify the surface as superhydrophobic. The storage conditions significantly affected this process. When the samples were stored in CO2, O2 and N2 atmospheres, the wettability transition was restrained. However, the transition was accelerated in atmosphere that was rich with organic compounds. Moreover, the superhydrophobic surface could recover their original superhydrophilicity by low temperature annealing. A detailed XPS analysis indicated that this wettability transition process was mainly caused by the adsorption of organic compounds from the surrounding atmosphere onto the oxide surface.

Superhydrophobic surfaces fabricated by femtosecond laser with tunable water adhesion: from lotus leaf to rose petal.

Superhydrophobic surfaces with tunable water adhesion have attracted much interest in fundamental research and practical applications. In this paper, we used a simple method to fabricate superhydrophobic surfaces with tunable water adhesion. Periodic microstructures with different topographies were fabricated on copper surface via femtosecond (fs) laser irradiation. The topography of these microstructures can be controlled by simply changing the scanning speed of the laser beam. After surface chemical modification, these as-prepared surfaces showed superhydrophobicity combined with different adhesion to water. Surfaces with deep microstructures showed self-cleaning properties with extremely low water adhesion, and the water adhesion increased when the surface microstructures became flat. The changes in surface water adhesion are attributed to the transition from Cassie state to Wenzel state. We also demonstrated that these superhydrophobic surfaces with different adhesion can be used for transferring small water droplets without any loss. We demonstrate that our approach provides a novel but simple way to tune the surface adhesion of superhydrophobic metallic surfaces for good potential applications in related areas.