Superhydrophobic “Pump”: Continuous and Spontaneous Antigravity Water Delivery

Antigravity transportation of water, which is often observed in nature, is becoming a vital demand for advanced devices and new technology. Many studies have been devoted to the motion of a single droplet on a horizontal or inclined substrate under specific assistance. However, the self‐propelled water motion, especially continuous antigravity water delivery, still remains a considerable challenge. Here, a novel self‐ascending phenomenon driven only by the surface energy release of water droplets is found, and a superhydrophobic mesh to pump water up to a height of centimeter scale is designed. An integrated antigravity transportation system is also demonstrated to continuously and spontaneously pump water droplets without additional driving forces. The present novel finding and integrated devices should serve as a source of inspiration for the design of advanced materials and for the development of new technology with exciting applications in microfluidics, microdetectors, and intelligent systems.     

An Autonomous Soft Actuator with Light‐Driven Self‐Sustained Wavelike Oscillation for Phototactic Self‐Locomotion and Power Generation

Mimicking the intelligence of biological organisms in artificial systems to design smart actuators that act autonomously in response to constant environmental stimuli is crucial to the construction of intelligent biomimetic robots and devices, but remains a great challenge. Here, a light‐driven autonomous carbon‐nanotube‐based bimorph actuator is developed through an elaborate structural design. This curled droplet‐shaped actuator can be simply driven by constant white light irradiation, self‐propelled by a light‐mechanical negative feedback loop created by light‐driven actuation, time delay in the photothermal response along the actuator, and good elasticity from the curled structure, performing a continuously self‐oscillating motion in a wavelike fashion, which mimics the human sit‐up motion. Moreover, this autonomous self‐oscillating motion can be further tuned by controlling the intensity and direction of the incident light. The autonomous actuator with continuous wavelike oscillating motion shows immense potential in light‐driven biomimetic soft robots and optical‐energy‐harvesting devices. Furthermore, a self‐locomotive artificial snake with phototaxis is constructed, which autonomously and continuously crawls toward the light source in a wave‐propagating manner under constant light irradiation. This snake can be placed on a substrate made of triboelectric materials to realize continuous electric output when exposed to constant light illumination.     

Remote Steering of Self‐Propelling Microcircuits by Modulated Electric Field

The principles and design of “active” self‐propelling particles that can convert energy, move directionally on their own, and perform a certain function is an emerging multidisciplinary research field, with high potential for future technologies. A simple and effective technique is presented for on‐demand steering of self‐propelling microdiodes that move electroosmotically on water surface, while supplied with energy by an external alternating (AC) field. It is demonstrated how one can control remotely the direction of diode locomotion by electronically modifying the applied AC signal. The swimming diodes change their direction of motion when a wave asymmetry (equivalent to a DC offset) is introduced into the signal. The data analysis shows that the ability to control and reverse the direction of motion is a result of the electrostatic torque between the asymmetrically polarized diodes and the ionic charges redistributed in the vessel. This novel principle of electrical signal‐coded steering of active functional devices, such as diodes and microcircuits, can find applications in motile sensors, MEMs, and microrobotics.     

Printing Nanostructures with a Propelled Anti‐Pinning Ink Droplet

Striving for cheap and robust manufacturing processes has prompted efforts to adapt and extend methods for printed electronics and biotechnology. A new “direct‐write” printing method for patterning nanometeric species in addressable locations has been developed, by means of evaporative deposition from a propelled anti‐pinning ink droplet (PAPID) in a manner analogous to a snail‐trail. Three velocity‐controlled deposition regimes have been identified; each spontaneously produces distinct and well‐defined self‐assembled deposition patterns. Unlike other technologies that rely on overlapping droplets, PAPIDs produce continuous patterns that can be formed on rigid or flexible substrates, even within 3D concave closed shapes, and have the ability to control the thickness gradient along the pattern. This versatile low cost printing method can produce a wide range of unusual electronic systems not attainable by other methods.     

Light‐Driven and Light‐Guided Microswimmers

Light‐driven swimming particles hold great potential in wide applications ranging from next‐generation drug delivery to versatile microrobotic devices. It is desired that the self‐propelled microparticles should swim not only autonomously but also directionally to achieve their goals in their potential applications. This paper presents the first example of fully organic colloidal particles of a spiropyran‐terminated hyperbranched polymer that can be driven and meanwhile steered by a UV light source, swimming straight towards the UV source. The mean‐square velocities of the photochromic suspension particles are about 20 μm s^?1, and increase to about 54 μm s^?1 with the addition of NaCl of 0.5%. The phototactic propulsion is supposed to be originated from the UV irradiation‐induced interfacial tension gradient on the surface of the colloidal particles. This finding allows for the design of new microengines for next‐generation drug delivery systems, microrobotic devices, and self‐adaptive photocatalysts, etc.     

Self‐Healing,Flexible, and Tailorable Triboelectric Nanogenerators for Self‐Powered Sensors based on Thermal Effect of Infrared Radiation

Self‐healing triboelectric nanogenerators (TENGs) with flexibility, robustness, and conformability are highly desirable for promising flexible and wearable devices, which can serve as a durable, stable, and renewable power supply, as well as a self‐powered sensor. Herein, an entirely self‐healing, flexible, and tailorable TENG is designed as a wearable sensor to monitor human motion, with infrared radiation from skin to promote self‐healing after being broken based on thermal effect of infrared radiation. Human skin is a natural infrared radiation emitter, providing favorable conditions for the device to function efficiently. The reversible imine bonds and quadruple hydrogen bonding (UPy) moieties are introduced into polymer networks to construct self‐healable electrification layer. UPy‐functionalized multiwalled carbon nanotubes are further incorporated into healable polymer to obtain conductive nanocomposite. Driven by the dynamic bonds, the designed and synthesized materials show excellent intrinsic self‐healing and shape‐tailorable features. Moreover, there is a robust interface bonding in the TENG devices due to the similar healable networks between electrification layer and electrode. The output electric performances of the self‐healable TENG devices can almost restore their original state when the damage of the devices occurs. This work presents a novel strategy for flexible devices, contributing to future sustainable energy and wearable electronics.     

Surfactant‐Assisted Emulsion Self‐Assembly of Nanoparticles into Hollow Vesicle‐Like Structures and 2D Plates

The emulsion‐based self‐assembly of nanoparticles into low‐dimensional superparticles of hollow vesicle‐like assemblies is reported. Evaporation of the oil phase at relatively low temperatures from nanoparticle‐containing oil‐in‐water emulsion droplets leads to the formation of stable and uniform sub‐micrometer vesicle‐like assembly structures in water. This result is in contrast with those from many previously reported emulsion‐based self‐assembly methods, which produce solid spherical assemblies. It is found that extra surfactants in both the oil and water phases play a key role in stabilizing nanoscale emulsion droplets and capturing hollow assembly structures. Systematic investigation into what controls the morphology in emulsion self‐assembly is carried out, and the approach is extended to fabricate more complex rattle‐like structures and 2D plates. These results demonstrate that the emulsion‐based assembly is not limited to typical thermodynamic spherical assembly structures and can be used to fabricate various types of interesting low‐dimensional assembly structures.     

Fully Solar‐Powered Uninterrupted Overall Water‐Splitting Systems

Extensive research efforts have been recently devoted to the development of self‐driven electrocatalytic water‐splitting systems to generate clean hydrogen chemical fuels. Currently, self‐driven electrocatalytic water‐splitting devices are powered by solar cells, which operate intermittently, or by aqueous batteries, which deliver stored electric power, leading to high operating costs and environmental pollution. Thus, a fully solar‐powered uninterrupted overall water‐splitting system is greatly desirable. Here, the solar cells, stable output voltage of 1.75 V Ni–Zn batteries, and high efficiency zinc–nickel–cobalt phosphide electrocatalysts are successfully assembled together to create a 24 h overall water‐splitting system. Specifically, the silicon‐based solar cells enable the charging of aqueous Ni–Zn batteries for energy storage as well as providing sufficient energy for electrocatalysis throughout the day; in addition, the high‐capacity Ni–Zn batteries offer a steady output voltage for overall water‐splitting at night. Such an uninterrupted solar‐to‐hydrogen system opens up exciting opportunities for the development and applications of renewable energy.     

All‐Printed Porous Carbon Film for Electricity Generation from Evaporation‐Driven Water Flow

Converting environmental “waste energies” into electricity via a natural process is an ideal strategy for environmental energy harvesting and supplying power for distributed energy‐consuming devices. This paper reports that evaporation‐driven water flow within an all‐printed porous carbon film can reliably generate sustainable voltage up to 1 V with a power density of ≈8.1 µW cm^?3 under ambient conditions. The output performance of the device can be easily scaled up and used to power low‐power consumption electronic devices or for energy storage. Furthermore, the device is successfully used without electric storage as a direct power source for electrodeposition of silver microstructures. Because of the ubiquity of water evaporation in nature and the low cost of materials involved, the study presents a novel avenue to harvest ambient energy and has potential applications in low‐cost, green, self‐powered devices and systems.     

Formation of Spherical and Non‐Spherical Eutectic Gallium‐Indium Liquid‐Metal Microdroplets in Microfluidic Channels at Room Temperature

Here, the formation of eutectic Gallium‐Indium (EGaIn) liquid‐metal microdroplets, both spherical and non‐spherical, in microfluidic devices at room temperature is reported. Monodisperse microdroplets were created in an aqueous polyethylene glycol (PEG) solution, in oxygenated and in deoxygenated silicone oil. The volume of the droplets depends on the channel dimensions and flow rates applied, varying between 0.5 and 4 nL. Non‐spherical droplets were formed in oxygenated silicone oil due to the instantaneous formation of an oxide layer. These metal “micro‐rice” droplets retained their shape and did not spontaneously reflow to form shapes of the lowest interfacial energy on egress from the channel, unlike in aqueous PEG solution and in deoxygenated silicone oil. Liquid‐metal droplets with such tunable morphology can potentially be used in MEMS devices for optical and electrical switches, valves and micropumps.     

Morphology‐Controlled Growth of Large‐Area Two‐Dimensional Ordered Pore Arrays

A solution‐dipping template strategy for large‐area synthesis of morphology‐controlled, ordered pore arrays is reported. The morphology of the pore array can easily be controlled by concentration of the precursor solution and treatment conditions. With decrease of the concentration from a high level to a very low level nanostructured complex (pore–hole, and pore–particle) arrays, through‐pore arrays, and even ring arrays can, in turn, be obtained. The pore size is adjustable over a large range by changing the diameter of the template's latex spheres. This synthesis route is universal and can be used for various metals, semiconductors and compounds on any substrate. Such structures may be useful in applications such as energy storage or conversion, especially in integrated next‐generation nanophotonics devices, and biomolecular labeling and identification.     

Self‐Propelled Tags for Protein Detection

Protein detection is of tremendous significance for biological and biomedical sciences. Because there is no equivalent of polymerase chain reaction available as a tool for protein detection, researchers must rely on tags to enhance the limits of detection. One of the crucial steps is the actual labeling of proteins, which relies on diffusion of the label, which is very slow, or external mixing of the label and protein is needed. Here, a conceptually new approach is demonstrated: self‐propelled tags that autonomously move in the solution and enhance protein detection. The tags used here are based on IrO₂/Pt bilayer microtubules, which can self‐propel and act as moving tags for enhanced protein electrochemical detection. This completely new label‐based protein detection concept using self‐propelled tag will find a wide spectrum of applications.     

Self‐Healing and Stretchable 3D‐Printed Organic Thermoelectrics

With the advent of flexible and wearable electronics and sensors, there is an urgent need to develop energy‐harvesting solutions that are compatible with such wearables. However, many of the proposed energy‐harvesting solutions lack the necessary mechanical properties, which make them susceptible to damage by repetitive and continuous mechanical stresses, leading to serious degradation in device performance. Developing new energy materials that possess high deformability and self‐healability is essential to realize self‐powered devices. Herein, a thermoelectric ternary composite is demonstrated that possesses both self‐healing and stretchable properties produced via 3D‐printing method. The ternary composite films provide stable thermoelectric performance during viscoelastic deformation, up to 35% tensile strain. Importantly, after being completely severed by cutting, the composite films autonomously recover their thermoelectric properties with a rapid response time of around one second. Using this self‐healable and solution‐processable composite, 3D‐printed thermoelectric generators are fabricated, which retain above 85% of their initial power output, even after repetitive cutting and self‐healing. This approach represents a significant step in achieving damage‐free and truly wearable 3D‐printed organic thermoelectrics.     

Bioinspired Self‐Propulsion of Water Droplets at the Convergence of Janus‐Textured Heated Substrates

Controlled propulsion of liquid droplets on a solid surface offers viable applications in fog harvesting, heat transfer, microfluidics, and microdevice technologies. A prerequisite for the propulsion of liquid droplets is to break the wetting symmetry of a droplet and contact‐line pinning on the surface by harnessing surface energy gradient. Here, a series of Janus‐textured substrates is constructed to investigate the self‐propulsion of Leidenfrost droplets. It is found that the self‐propulsion of droplets occurs only on two special Janus‐textured substrates. Those are nanostructured silicon substrate bounded by smooth silicon substrate and the nanowire‐decorated microstructured silicon substrate bounded by micropillars with smooth surfaces. The difference in roughness between the two sides of the Janus‐textured substrates creates various numbers and sizes of vapor bubbles. The vapor bubbles cause the droplets to become turbulent, and a pressure gradient is generated. The sufficiently large pressure gradient propels the Leidenfrost droplet to move directionally. The propulsion direction is always toward areas with low roughness.     

Acceptance‐Diffusion Strategies for Tablet‐PCs: Focused on Acceptance Factors of Non‐Users and Satisfaction Factors of Users

Among emerging devices propelling the growth of mobile devices, smartphones and tablet‐PCs are among the most recognizable. In this study, a research model is designed for exploring acceptance‐diffusion strategies for tablet‐PCs from the viewpoint of consumer perception, which is verified through a survey. The results of this study show that tablet‐PCs have great potential to be versatile, multifunctional devices, even though they are currently considered mostly as entertainment‐oriented rather than fulfilling the essential needs of everyday life. An analysis of the acceptance model for tablet‐PCs revealed that playability, cost level, functionality, and complexity significantly affect user acceptance. An analysis of the diffusion model, on the other hand, showed that playability and user interface have a significant influence on satisfaction, trust, and positive behavioral intention. We also found that cost level is not a major hindrance in the market diffusion of tablet‐PCs. The results of this study can be used to establish effective acceptance and diffusion strategies for tablet‐PCs and other emerging devices.     

Functionally Cooperating Mini‐Generator: From Bacterial Fermentation to Electricity

Mini‐generators based on Faraday's law have exploited a new application of self‐propelled micromotors in energy conversion. However, most such mini‐generators normally consume high‐grade energy to produce low electric energy and lack applicable occasions. Herein, a mini‐generator is designed that harvests low‐grade internal energy of gas from a fermentation line for successive conversion to kinetic energy of reciprocating motions and finally to electric energy without harming the fermentation production. The problem of irregular release of fermentative bubbles resulting in disordered motions is solved by the design of a superhydrophobic cushion valve, which regulates bubble releases to ensure periodic surfacing–diving motions and stable electricity generation. The mini‐generator has a lifetime over 20 000 s with the maximum induced voltage of 2.4 V, which is sufficient to light a dozen red LEDs and energy conversion efficiency reaches 40%. Moreover, the mini‐generator is used back to the fermentation line as a real‐time gas flowmeter. By integrating mini‐generators with industrial fermentation lines, this work has provided an effective strategy to minimize energy input and maximize energy output of mini‐generators by collecting weak environmental energy and meanwhile exploited practical uses of mini‐generators with low output.     

Highly Efficient and Water‐Insensitive Self‐Healing Elastomer for Wet and Underwater Electronics

Integrating self‐healing capabilities into soft electronic devices increases their durability and long‐term reliability. Although some advances have been made, the use of self‐healing electronics in wet and/or (under)water environments has proven to be quite challenging, and has not yet been fully realized. Herein, a new highly water insensitive self‐healing elastomer with high stretchability and mechanical strength that can reach 1100% and ≈6.5 MPa, respectively, is reported. The elastomer exhibits a high (>80%) self‐healing efficiency (after ≈ 24 h) in high humidity and/or different (under)water conditions without the assistance of an external physical and/or chemical triggers. Soft electronic devices made from this elastomer are shown to be highly robust and able to recover their electrical properties after damages in both ambient and aqueous conditions. Moreover, once operated in extreme wet or underwater conditions (e.g., salty sea water), the self‐healing capability leads to the elimination of significant electrical leakage that would be caused by structural damages. This highly efficient self‐healing elastomer can help extend the use of soft electronics outside of the laboratory and allow a wide variety of wet and submarine applications.     

Bringing Hetero‐Polyacid‐Based Underwater Adhesive as Printable Cathode Coating for Self‐Powered Electrochromic Aqueous Batteries

The advent of electrochromic aqueous batteries represents a promising trend in the development of smart and environmentally friendly energy storage devices. However, it remains a great challenge to integrate electrochromic, flexible, and patterned features into a single battery unit through a simple operation. Herein, an entirely new class of hetero‐polyacid‐based underwater adhesives is designed and synthesized by combining the redox properties of hetero‐polyacids and the water‐resistant binding of adhesives in single system. The hybrid underwater adhesives not only serve as printable electrode coatings in aqueous solution but also offer unique electrochromic feature for guiding the convenient fabrication of self‐powered electrochromic aqueous battery. The reversible discharging and H₂O₂ assistant charging behavior is also demonstrated. This kind of wet and electrochromic adhesive with excellent toleration of mechanical deformation offers great promise in developing flexible and smart energy storage configuration, which provides a user‐device interface platform allowing one to evaluate the battery's charging state based on the naked eye–visible change in color.     

Porphyrin‐ and Fullerene‐Based Molecular Photovoltaic Devices

We have developed a novel strategy for the construction of molecular photovoltaic devices where the porphyrins and fullerenes employed as building blocks are organized into nanostructured artificial photosynthetic systems by self‐assembly processes. Highly efficient photosynthetic energy‐ and electron‐transfer processes take place at gold and indium tin oxide (ITO) electrodes modified with self‐assembled monolayers of porphyrin‐ or fullerene linked systems. Porphyrins and fullerenes have also been assembled step by step to make large and uniform clusters on nanostructured semiconductor electrodes, which exhibit a high power‐conversion efficiency of close to 1 %. These results will provide valuable information on the design of donor–acceptor‐type molecular assemblies that can be tailored to construct highly efficient photovoltaic devices.     

Touch‐Interactive Flexible Sustainable Energy Harvester and Self‐Powered Smart Card

Sustainable and safe energy sources combined with cost effectiveness are major goals for society when considering the current scenario of mass production of portable and Internet of Things (IoT) devices along with the huge amount of inevitable e‐waste. The conceptual design of a self‐powered “eco‐energy” smart card based on paper promotes green and clean energy, which will bring the zero e‐waste challenge one step closer to fruition. A commercial raw filter paper is modified through a fast in situ functionalization method, resulting in a conductive cellulose fiber/polyaniline composite, which is then applied as an energy harvester based on a mechano‐responsive charge transfer mechanism through a metal/conducting polymer interface. Different electrodes are studied to optimize charge transfer based on contact energy level differences. The highest power density and current density obtained from such a paper‐based “eco‐energy” smart card device are 1.75 W m^?2 and 33.5 mA m^?2 respectively. This self‐powered smart energy card is also able to light up several commercial light‐emitting diodes, power on electronic devices, and charge capacitors.