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Liquid manipulation using tubular actuators finds diverse applications ranging from microfluidics, printing, liquid transfer to micro‐reactors. Achieving flexible and simple regulation of manipulated liquid droplets during transport is crucial for the tubular liquid actuators to perform complex and multiple functions, yet it remains challenging. Here, a facile tubular actuator for directional transport of various liquid droplets under the control of an externally applied magnetic field is presented. The surfaces of the actuator can be engineered with submillimeter‐sized through‐hole pores, which enables the liquid droplet to be easily modulated in the transport process. Furthermore, the liquid actuator with featured through‐hole pores is expanded to function as a switch in an integrated external electric circuit by magnetically controlling the motion of a conductive liquid droplet. This work develops a strategy for regulating liquid droplets in the tubular actuation systems, which may inspire ideas for designing functional liquid actuators with potential applications in microfluidics, microchemical reaction, liquid switch, and liquid robotics. [ABSTRACT FROM AUTHOR]

Asymmetric mechanical transducers have important applications in energy harvesting, signal transmission, and micro-mechanics. To achieve asymmetric transformation of mechanical motion or energy, active robotic metamaterials, as well as materials with asymmetric microstructures or internal orientation, are usually employed. However, these strategies usually require continuous energy supplement and laborious fabrication, and limited transformation modes are achieved. Herein, utilizing wettability patterned surfaces for precise control of the droplet contact line and inner flow, we demonstrate a droplet-based mechanical transducer system, and achieve multimodal responses to specific vibrations. By virtue of the synergistic effect of surface tension and solid-liquid adhesion on the liquid dynamics, the droplet on the patterned substrate can exhibit symmetric/asymmetric vibration transformation when the substrate vibrates horizontally. Based on this, we construct arrayed patterns with distinct arrangements on the substrate, and employ the swarm effect of the arrayed droplets to achieve three-dimensional and multimodal actuation of the target plate under a fixed input vibration. Further, we demonstrate the utilization of the mechanical transducers for vibration management, object transport, and laser modulation. These findings provide a simple yet efficient strategy to realize a multimodal mechanical transducer, which shows significant potential for aseismic design, optical molding, as well as micro-electromechanical systems (MEMS). Asymmetric mechanical transducers are pivotal in various applications; however, conventional methods demand continuous energy and intricate fabrication. Here, the authors demonstrate a droplet-based mechanical transducer utilizing wettability-patterned surfaces, enabling precise control of droplet dynamics. [ABSTRACT FROM AUTHOR]

Selective and deterministic assembly of particles is fundamentally significant for manufacturing functional devices. However, it is still a challenge to precisely and facilely manipulate particles of different sizes into different assembly patterns. Herein, a method is presented to achieve precise control over the formation of binary or ternary particle size‐sorted assemblies. We investigate the assembly process of particles by capillary confinement and show that different size‐sorted assemblies of multiple components can be realized by tuning the templated dewetting. By controlling the dewetting direction, receding contact angle, and pillar height of the template, assembly of dual‐ring patterns, "comet" structures, and patterns with component separation are regulated. These structures can be further diversified by tuning the composition of the particles. This approach is general for particle assemblies of different sizes and materials, which will be significant for the fabrication of printed micro/nanohybrid devices. Guided assembly: An efficient method is presented to achieve precise control over the particle size‐sorted assembly of different patterns from binary or ternary mixtures by controlling the templated dewetting behavior. The method is used to generate dual‐ring patterns, "comet" structures, and separated component patterns. [ABSTRACT FROM AUTHOR]

Abstract: Surface‐enhanced Raman scattering (SERS) provides an approach for the label‐free and miniaturized detection of the trace amount of analyte molecules. A SERS microchip of Au‐areoles array, mimicking the areole on the cactus, is facilely and controllably prepared through selectively electrochemical deposition on patterned superhydrophilic–superhydrophobic substrates. The Au‐areoles are full of SERS hot spots thanks to the large amounts of sharp edges, tips, and coupled branches. Meanwhile, the superhydrophilic sites on the superhydrophobic substrate can collect the target molecules into those hot spots. The combination of the SERS enhancement of the nanostructured‐Au and the collective effect of the superhydrophilic–superhydrophobic pattern endows the microchip with sample‐effective, ultrasensitive, and efficient Raman detection capabilities, which are demonstrated by integrated detection of femtomol Rhodamine 6G and diverse bioanalytes. The chip can also be used for mutually independent multisample detection without interference. [ABSTRACT FROM AUTHOR]

The performance of large-area perovskite solar cells (PSCs) is confined to the non-uniformity edge-coating and crystalline defects. Focusing on the critical requirement of large-area uniform and compact crystallized perovskite film for efficient PSCs, here, an inkjet manipulated approach is introduced for controlling the thin-film perovskite growth in a mesoporous solar cell device structure. The ink droplet wetting behavior on mesoporous substrate, the physical properties of solutions have been systematically investigated. Uniform liquid membrane was obtained via precisely controlled micro-droplets by inkjet-printing. Mesoporous substrates guarantee fast and complete coalescence of the precursor droplets, and limit random diffusion of the precursor solution. Homogeneous PbI 2 film leads to a compact perovskite film with micro-scale crystalline grains, which enables PSCs high power conversion efficiencies (PCEs) of 18.64% for small area (0.04 cm 2 ) and 17.74% for large area (2.02 cm 2 ). The enhanced performance can be ascribed to improved uniformity of the perovskite film morphology, favorable perovskite crystallite orientation, large grain size (> 2 µm) and less grain boundaries. Inkjet manipulation provides a facile approach to fabricate large-area and high-quality films for future optoelectronics, including field effect transistors, light-emitting diodes, and sensor devices. [ABSTRACT FROM AUTHOR]

Abstract: The formation of polystyrene (PS) sphere nanostructures through vertical deposition can provide large surface roughness, which effectively enhances the hydrophobicity of the films. Moreover, well-ordered PS sphere arrays bring about structural colors, which can be controlled through the sphere diameter. All the water contact angles of colloidal crystal films prepared from monodisperse PS sphere solutions with diameters from 225 to 605 nm were larger than 120°, showing highly hydrophobic character. [Copyright &y& Elsevier]

Superhydrophobic surfaces have aroused great attention for promising applications, e.g., anti-ice/frost. However, most surfaces which are superhydrophobic at room temperature lose their superhydrophobicity at low surface temperatures. Here, surfaces with different area fractions of the solid surface in contact with the liquid (f1) were designed. It is found that surfaces with f1 equal to or smaller than 0.068 maintain the superhydrophobicity when the surface temperature approaches the dew-point. These results are crucial to understand the correlation between the surface morphology and the superhydrophobicity around the dew-point, and design effective surfaces with desired wettability. [ABSTRACT FROM AUTHOR]

We investigate wetting behaviors of two kinds of hydrophilic ordered nanoporous anodic alumina (PAA). The water contact angle (CA) increases at first and subsequently decreases with increasing pore diameter of PAA with closed-pore structure, while the water CA decreases monotonously on PAA with open-pore structure. These interesting wetting behaviors are mainly due to the presence/absence of closed-air in the PAA. The closed-air could prevent water from entering into the nanopores. This work offers insight to control wetting by tailoring the surface nanostructure and will be significant for applications in printing, coating, etc. [ABSTRACT FROM AUTHOR]

3D printing has become one of the most promising methods to construct delicate 3D structures. However, precision and material utilization efficiency are limited. Here, we propose a one-droplet 3D printing strategy to fabricate controllable 3D structures from a single droplet ascribing to the receding property of the three-phase contact line (TCL) of the resin droplet. The well-controlled dewetting force of liquid resin on the cured structure results in the minimization of liquid residue and the high wet and net material utilization efficiency in forming a droplet into a 3D structure. Additionally, extra curing induced protruding or stepped sidewalls under high printing speed, which require high UV intensity, can be prevented. The critical is the free contact surface property of the droplet system with the introduction of the receding TCL, which increased the inner droplet liquid circulation and reduces the adhesion properties among the liquid resin, cured resin, and resin vat. Digital light processing and stereolithography have low wet material utilization efficiency. Here the authors propose a one-droplet 3D printing strategy to fabricate 3D structures from a single resin droplet. [ABSTRACT FROM AUTHOR]

Soft Acoustic Metamaterials: Bubble Architectures for Locally Resonant Acoustic Metamaterials (Adv. Funct. In article number 1906984, Zhandong Huang, Yanlin Song, and co-workers develop a general method for fabricating soft acoustic metamaterials based on bubble architectures by combining 3D printing and surface hydrophobic properties. Moreover, a water-to-air ultratransmission metasurface is prepared by patterning a layer of bubbles beneath the water surface, which allows for ultratransmission of sound across an air-water interface. [Extracted from the article]

Soft acoustic metamaterials that embed soft materials in a host media have promising applications in aqueous environments. However, the preparation of soft metamaterials under water and realization of low‐frequency soft acoustic metamaterials remains a challenge. By combining 3D printing technology and surface hydrophobic properties, this work presents a general approach to construct 3D soft acoustic metamaterials using bubbles as resonator units. Low‐frequency broadband locally resonant metamaterials can be realized using patterned bubbles with bandgaps that are orders of magnitude wider than other locally resonant metamaterials. In addition, a water‐to‐air ultratransmission metasurface is prepared by patterning a layer of bubbles beneath the water surface, which allows for the ultratransmission of sound across an air–water interface. This strategy opens up promising avenues for many applications based on locally resonant metamaterials such as deep subwavelength acoustic superlenses or negative‐refraction metamaterials. [ABSTRACT FROM AUTHOR]

Highlights from the article: Keywords: competitive growth; micro-contact print; perovskites; solar cells; surface wettability In article number 1900838, Mingzhu Li, Yanlin Song and co-workers report a competitive perovskite grain growth approach via a micro-contact print (MicroCP) method with CD discs as templates for printing a wettability-patterned substrate, to achieve a large-grained perovskite and avoid discontinuous perovskite films caused by the low wettability of substrates, resulting in efficiencies over 20% for the MicroCP perovskite solar cells. Competitive growth, micro-contact print, perovskites, solar cells, surface wettability.

Novel photovoltaic perovskite solar cells (PSCs) with high‐efficient photovoltaic property are largely in thrall to the uncertain perovskite grain size and inevitable defects. Here, inspired by the competitive growth between tree and grass in the forest system, a competitive perovskite grain growth approach via micro‐contact print (MicroCP) method (CD disk as templates) for printing wettability‐patterned substrate is proposed, aiming to achieve large‐grained perovskite and avoid discontinuous perovskite films caused by the low wettability of substrates. A MicroCP process is employed to construct a patterned wettability surface for the perovskite competitive growth mechanism on the electrode surface. This approach modifies the substrates quickly, ensures the uniform coverage of perovskite due to the function of ‐NH2 and Pb2+ bonds, and converts the perovskite films composed of small grains and pinholes into high‐quality perovskite films, free from pinholes and made up of large grains, resulting in efficiencies over 20% for the MicroCP PSCs. [ABSTRACT FROM AUTHOR]

On page 2237, Y. Song, F. Y. Li, and co‐workers demonstrate a facile strategy to directly print controllable 3D structures and morphologies from one droplet. Through designing hydrophilic pattern on hydrophobic surface, the surface energy difference results in asymmetric retraction of the three phase contact line, which leads to various 3D structures. This idea to precisely print the 3D structures could open a new avenue for controllable 3D manufacture. [ABSTRACT FROM AUTHOR]