Magnetically Induced Fog Harvesting via Flexible Conical Arrays

Water is the driving force of all nature. Securing freshwater has been one of the most important issues throughout human history, and will be important in the future, especially in the next decade. Fog is ubiquitous in nature and is therefore considered as an alternative and sustainable freshwater resource. Nature has long served as a source of inspiration to develop new fog‐harvesting technologies. However, the collection of freshwater from static fog is still a challenge for the existing bio‐inspired fog‐harvesting systems. Herein, magnetically induced fog harvesting under windless conditions through the integration of cactus‐inspired spine structures and magnetically responsive flexible conical arrays is reported. Under an external magnetic field, static fog can be spontaneously and continuously captured and transported from the tip to the base of the spine due to the Laplace pressure difference. This work demonstrates the advantage of collecting fog water, especially in windless regions, which provides a new avenue for fog harvesting and can serve as a source of inspiration to further optimizations of existing fog‐water‐harvesting strategies.     

Cactus Stem Inspired Cone‐Arrayed Surfaces for Efficient Fog Collection

With the increasing world population and the rapid development of the global industry, clean water is becoming scarcer and scarcer. Means of translating latent water in fog to dominant available water, i.e., fog collection, therefore becomes highly desirable. Previously, it was demonstrated that the cactus O. Microdasys has an integrated fog collection system arising from the evenly distributed clusters of spines and trichomes on the cactus stem. Here, it is reported that the intersite of the clusters on the cactus stem is densely covered with cones, which are also capable of collecting water from fog efficiently. Inspired by these cones, using a simple method combining mechanical perforating and template replica technology, polydimethylsiloxane (PDMS) cone arrays are fabricated with different arrangements and the one in hexagonal arrangement proves to be more efficient due to the more turbulent flow filed around the staggered cones and the rapid directional movement of water drops along each cone. This investigation opens up new avenue to collect water efficiently and may also provide clues to research about dust filtering and smog removal, which is attracting increasing attention worldwide.     

Layered data aggregation with efficient privacy preservation for fog‐assisted IIoT

The emergence of fog computing facilitates industrial Internet of Things (IIoT) to be more real‐time and efficient; in order to achieve secure and efficient data collection and applications in fog‐assisted IIoT, it usually sacrifices great computation and bandwidth resources. From the low computation and communication overheads perspective, this paper proposes a layered data aggregation scheme with efficient privacy preservation (LDA‐EPP) for fog‐assisted IIoT by integrating the Chinese remainder theorem (CRT), modified Paillier encryption, and hash chain technology. In LDA‐EPP scheme, the entire network is divided into several subareas; the fog node and cloud are responsible for local and global aggregations, respectively. Specially, the cloud is able to obtain not only the global aggregation result but also the fine‐grained aggregation results of subareas, which enables that can provide fine‐grained data services. Meanwhile, the LDA‐EPP realizes data confidentiality by the modified Paillier encryption, ensures that both outside attackers and internal semi‐trusted nodes (such as, fog node and cloud) are unable to know the privacy data of individual device, and guarantees data integrity by utilizing simply hash chain to resist tempering and polluting attacks. Moreover, the fault tolerance is also supported in our scheme; ie, even though some IIoT devices or channel links are failure, the cloud still can decrypt incomplete aggregation ciphertexts and derive expected aggregation results. Finally, the performance evaluation indicates that our proposed LDA‐EPP has less computation and communication costs.     

Bio-inspired Copper Kirigami Motifs Leading to a 2D–3D Switchable Structure for Programmable Fog Harvesting and Water Retention

Bio-inspired fog harvesting devices (FHDs) have been exploited to address water shortages. Despite the advances achieved, efficient and continuous fog harvesting is still hindered by some challenges: 1) a single mechanism appears to be insufficient to achieve optimal water collection efficiency; 2) the re-evaporation of the harvested water results in decreased water collection. In this study, inspired by the unique feature of cacti, Nepenthes alata, lotus leaves, and pinecones, a 2D–3D switchable copper sheet (SLP-SHL@SP-Cu) is reported, which results in excellent fog capture and water transport rates. During the fog harvesting process, the captured droplets transport from the tip of the top surface to the bottom under the Laplace forces (cacti spine), capillary forces (lotus leaves), and low surface energy (Nepenthes alata). Notably, the novel FHD responds in a preprogrammed manner to changes in humidity and performs a dynamic transformation from a 2D planar structure to a 3D helical structure (and in reverse), enabling efficient fog harvesting (in the 3D geometry) and water storage (in its 2D form). Thus, this study opens a new avenue for the practical applications of highly effective FHDs with increased water retention abilities.     

An Innovative Design by Single‐Layer Superaerophobic Mesh: Continuous Underwater Bubble Antibuoyancy Collection and Transportation

Underwater bubbles are unavoidable in the natural world and industrial production. Understanding the behavior of underwater bubbles and manipulating gas bubbles are vital important to both fundamental scientific research and industrial application. Although there has been some progress in controlling underwater bubbles, continuous underwater bubble collection and transportation remain challenging targets. Herein, inspired by the mechanism of water spider's gas storage, a strategy to collect and transport underwater gas bubble is demonstrated by design of a single‐layer underwater superaerophobic mesh (USM) assembled with a quartz tube. Gas bubbles supplied by a syringe pump penetrate the mesh pore and then gather to form a gas column in the quartz tube. Collapse occurs when the gas column reach the maximum storage height/pressure. Under a continuous supply of gas bubbles, the change of pressure becomes a cyclic process, which acts in a pump‐like manner to transport bubbles continuously from the water to the gas phase in the USM device assembled with an asymmetric U‐tube. This novel gas collection and transport system provides a new inspiration for developing new technologies for applications in pipes, sensors, gas collection, and environment protection.     

A Spider‐Capture‐Silk‐Like Fiber with Extremely High‐Volume Directional Water Collection

A spider web collects water by its capture silk for recovering the daytime‐distorted shape during night through water‐sensitive shape memory effect. This unique smart function and geometrical structure of spider‐capture‐silk inspires the development of artificial fibers with periodic knots for directional water collection with vast potential applications in water scarce regions. Existing such fibers are mainly based on nylon filaments coated with petroleum‐originated synthetic polymer solutions. Distinct from using synthetic materials, an all silk‐protein fiber (ASPF) with periodic knots endows extremely high volume‐to‐mass water collection capability. This fiber has a main body consisting of B. mori degummed silk coated with recombinant engineered major ampullate spidroin 2 of spider dragline silk. It is 252 times lighter than synthetic polymer coated nylon fibers that once was reported to have the highest water collection performance. The ASPF collects a maximum water volume of 6.6 µL and has a 100 times higher water collection efficiency compared to existing best water collection artificial fibers in terms of volume‐to‐mass index at the shortest length (0.8 mm) of three‐phase contact line. Since silkworm silks are available abundantly, effective use of recombinant spidroins tandemly shows great potential for scalability.     

Mussel‐Inspired Hydrogels for Self‐Adhesive Bioelectronics

Wearable and implantable bioelectronics are receiving a great deal of attention because they offer huge promise in personalized healthcare. Currently available bioelectronics generally rely on external aids to form an attachment to the human body, which leads to unstable performance in practical applications. Self‐adhesive bioelectronics are highly desirable for ameliorating these concerns by offering reliable and conformal contact with tissue, and stability and fidelity in the signal detection. However, achieving adequate and long‐term self‐adhesion to soft and wet biological tissues has been a daunting challenge. Recently, mussel‐inspired hydrogels have emerged as promising candidates for the design of self‐adhesive bioelectronics. In addition to self‐adhesiveness, the mussel‐inspired chemistry offers a unique pathway for integrating multiple functional properties to all‐in‐one bioelectronic devices, which have great implications for healthcare applications. In this report, the recent progress in the area of mussel‐inspired self‐adhesive bioelectronics is highlighted by specifically discussing: 1) adhesion mechanism of mussels, 2) mussel‐inspired hydrogels with long‐term and repeatable adhesion, 3) the recent advance in development of hydrogel bioelectronics by reconciling self‐adhesiveness and additional properties including conductivity, toughness, transparency, self‐healing, antibacterial properties, and tolerance to extreme environment, and 4) the challenges and prospects for the future design of the mussel‐inspired self‐adhesive bioelectronics.     

Nature‐inspired meta‐heuristic algorithms for solving the load balancing problem in the software‐defined network

The growth of the networks has difficult network management. Recently, a concept called software‐defined network (SDN) has been proposed to address this issue, which makes network management more adaptable. Control and forwarding planes are separated in SDN. The control plane is a centralized logical controller that controls the network. The forwarding plane that consists of transfer devices is responsible for transmitting packets. Because the network resources are limited, optimizing the use of resources in the networks is an important issue. Load balancing improves the balanced distribution of loads across multiple resources in order to maximize the reliability and network resources efficiency. SDN controllers can create an optimal load balancing compared to traditional networks because they have a network global view. The load‐balancing problem can be solved using many different nature‐inspired meta‐heuristic techniques because it has the NP‐complete nature. Hence, for solving load balancing problem in SDN, nature‐inspired meta‐heuristic techniques are important methods. However, to the best of our knowledge, there is not a survey or systematic review on studying these matters. Accordingly, in the area of the load balancing in the SDN, this paper reviews systematically the nature‐inspired meta‐heuristic techniques. Also, this study demonstrates advantages and disadvantages regarded of the chosen nature‐inspired meta‐heuristic techniques and considers their algorithms metrics. Moreover, to apply better load balancing techniques in the future, the important challenges of these techniques have been investigated.     

The study of the charge collection of the normal‐collector configuration

Charge collection is one of the crucial processes to collect the induced current when a semiconductor sample is subjected to some external excitations such as the electron or photon beams. The charge collection probability is the basis in the study of this induced current particularly in the field of photonic devices, photovoltaic cells as well as in the characterization of semiconductor materials and devices. In this paper, the analytical expressions for the charge collection probability of the finite‐dimension normal‐collector configuration, with and without surface recombination at the free surfaces are presented. An excellent agreement has been found between the charge collection probability profiles computed using the presently derived analytical expressions and those obtained using a device simulator. The results have been used to study the effects of the various physical parameters on the charge collection probability. These analytical expressions are expected to enhance our understanding of the charge collection process. Copyright © 2012 John Wiley & Sons, Ltd.     

Mussel‐Inspired Adhesive and Conductive Hydrogel with Long‐Lasting Moisture and Extreme Temperature Tolerance

Conductive hydrogels are a promising class of materials to design bioelectronics for new technological interfaces with human body, which are required to work for a long‐term or under extreme environment. Traditional hydrogels are limited in short‐term usage under room temperature, as it is difficult to retain water under cold or hot environment. Inspired by the antifreezing/antiheating behaviors from nature, and based on mussel chemistry, an adhesive and conductive hydrogel is developed with long‐lasting moisture lock‐in capability and extreme temperature tolerance, which is formed in a binary‐solvent system composed of water and glycerol. Polydopamine (PDA)‐decorated carbon nanotubes (CNTs) are incorporated into the hydrogel, which assign conductivity to the hydrogel and serve as nanoreinforcements to enhance the mechanical properties of the hydrogel. The catechol groups on PDA and viscous glycerol endow the hydrogel with high tissue adhesiveness. Particularly, the hydrogel is thermal tolerant to maintain all the properties under extreme wide tempreature spectrum (?20 or 60 °C) or stored for a long term. In summary, this mussel‐inspired hydrogel is a promising material for self‐adhesive bioelectronics to detect biosignals in cold or hot environments, and also as a dressing to protect skin from injuries related to frostbites or burns.     

A Natural Silk Fibroin Protein‐Based Transparent Bio‐Memristor

The recent discovery of nanoelectronics memristor devices has opened up a new wave of enthusiasm and optimism in revolutionizing electronic circuit design, marking the beginning of new era for the advancement of neuromorphic, high‐density logic and memory applications. Here a highly non‐linear dynamic response of a bio‐memristor is demonstrated using natural silk cocoon fibroin protein of silkworm, Bombyx mori. A film that is transparent across most of the visible spectrum is obtained with the electronic‐grade silk fibroin aqueous solution of ca. 2% (wt/v). Bipolar memristive switching is demonstrated; the switching mechanism is confirmed to be the filamentary switching as observed by probing local conduction behavior at nanoscale using scanning tunneling microscopy. The memristive transition is elucidated by a physical model based on the carrier trapping or detrapping in silk fibroin films and this appears to be due to oxidation and reduction procedures, as evidenced from cyclic voltammetry measurements. Hence, silk fibroin protein could be used as a biomaterial for bio‐memristor devices for applications in advanced bio‐inspired very large scale integration circuit design as well as in biologically inspired synapse links for energy‐efficient neuromorphic computing.     

Fingerprint‐Inspired Conducting Hierarchical Wrinkles for Energy‐Harvesting E‐Skin

In the field of bionics, sophisticated and multifunctional electronic skins with a mechanosensing function that are inspired by nature are developed. Here, an energy‐harvesting electronic skin (energy‐E‐skin), i.e., a pressure sensor with energy‐harvesting functions is demonstrated, based on fingerprint‐inspired conducting hierarchical wrinkles. The conducting hierarchical wrinkles, fabricated via 2D stretching and subsequent Ar plasma treatment, are composed of polydimethylsiloxane (PDMS) wrinkles as the primary microstructure and embedded Ag nanowires (AgNWs) as the secondary nanostructure. The structure and resistance of the conducting hierarchical wrinkles are deterministically controlled by varying the stretching direction, Ar plasma power, and treatment time. This hierarchical‐wrinkle‐based conductor successfully harvests mechanical energy via contact electrification and electrostatic induction and also realizes self‐powered pressure sensing. The energy‐E‐skin delivers an average output power of 3.5 mW with an open‐circuit voltage of 300 V and a short‐circuit current of 35 µA; this power is sufficient to drive commercial light‐emitting diodes and portable electronic devices. The hierarchical‐wrinkle‐based conductor is also utilized as a self‐powered tactile pressure sensor with a sensitivity of 1.187 mV Pa^‐1 in both contact‐separation mode and the single‐electrode mode. The proposed energy‐E‐skin has great potential for use as a next‐generation multifunctional artificial skin, self‐powered human–machine interface, wearable thin‐film power source, and so on.     

Cactus‐Like NiCoP/NiCo‐OH 3D Architecture with Tunable Composition for High‐Performance Electrochemical Capacitors

To effectively enhance the energy density and overall performance of electrochemical capacitors (ECs), a new strategy is demonstrated to increase both the intrinsic activity of the reaction sites and their density. Herein, nickel cobalt phosphides (NiCoP) with high activity and nickel cobalt hydroxides (NiCo‐OH) with good stability are purposely combined in a hierarchical cactus‐like structure. The hierarchical electrode integrates the advantages of 1D nanospines for effective charge transport, 2D nanoflakes for mechanical stability, and 3D carbon cloth substrate for flexibility. The NiCoP/NiCo‐OH 3D electrode delivers a high specific capacitance of ≈1100 F g^?1, which is around seven times higher than that of bare NiCo‐OH. It also possesses ≈90% capacitance retention after 1000 charge–discharge cycles. An asymmetric supercapacitor composed of NiCoP/NiCo‐OH cathode and metal–organic framework‐derived porous carbon anode achieves a specific capacitance of ≈100 F g^?1, high energy density of ≈34 Wh kg^?1, and excellent cycling stability. The cactus‐like NiCoP/NiCo‐OH 3D electrode presents a great potential for ECs and is promising for other functional applications such as catalysts and batteries.     

A Printable Metallic Current Collector for All‐Printed High‐Voltage Micro‐Supercapacitors: Instantaneous Surface Passivation by Flash‐Light‐Sintering Reaction

Recently, a printable power source that can be implemented on demand in integrated circuitries has gained tremendous attention to facilitate next‐generation, form‐factor free, miniaturized electronic systems. Among various energy storage units, a solid‐state micro‐supercapacitor with in‐plane device architecture has been recognized as a viable candidate with characteristic advantages of long cycle life‐time, high frequency response, and fast charge/discharge rate. However, to date, high performance, all‐printed micro‐supercapacitors have rarely been reported owing to an absence of printable current collector materials that can sustain high voltage conditions. In this study, a multidimensional printable particle mixture comprising Ni nanoparticles, Ni flakes, and a photoreactive polymer, polyvinylpyrrolidone is proposed. The highly conductive, printed metallic current collector is generated with a conductive surface passivation layer in a timescale of 10^?3 s by flash‐light sintering process. It is revealed that the resulting metallic current collector is stable at a voltage as high as 3 V in the carbon electrode‐based device, enabling the fabrication of an all‐printed solid‐state micro‐supercapacitor with an areal energy density of 79–23 mJ cm^?2 at an areal power density of 0.4–12.8 mW cm^?2. Arbitrarily designed device circuits can be generated on demand simply by using a digitally programmable printing process, without incorporation of additional interconnection lines.     

A Bio‐inspired Potassium and pH Responsive Double‐gated Nanochannel

Bio‐inspired nanochannels have emerged as an interface to mimic the functionalities of biological nanochannels. One remaining challenge is to develop double‐gated nanochannels with dual response, which can regulate the ion transport direction by alternately opening and closing the two gates. In this work, a bio‐inspired potassium and pH responsive double‐gated nanosystem is presented, constructed through immobilizing C‐quadruplex and G‐quadruplex DNA molecules onto the top and bottom tip side of a cigar‐shaped nanochannel, respectively. It is demonstrated that the two gates of the nanochannel can be opened and closed alternately/simultaneously. This phenomenon results from the attached DNA conformational transition caused by adjusting the concentrations of potassium ion and proton. This design is believed to be the first example of dual‐responsive double‐gated nanosystem, and paves a new way to investigate more intelligent bio‐inspired nanofluidic system.     

A Photoresponsive Red‐Hair‐Inspired Polydopamine‐Based Copolymer for Hybrid Photocapacitive Sensors

Inspired by the powerful photosensitizing properties of the red hair pigments pheomelanins, a photoresponsive cysteine‐containing variant of the adhesive biopolymer polydopamine (pDA) is developed via oxidative copolymerization of dopamine (DA) and 5‐S‐cysteinyldopamine (CDA) in variable ratios. Chemical and spectral analysis indicate the presence of benzothiazole/benzothiazine units akin to those of pheomelanins. p(DA/CDA) copolymers display ­impedance properties similar to those of biological materials and a marked photoimpedance response to light stimuli. The use of the p(DA/CDA) copolymer to implement a solution‐processed hybrid photocapacitive/resistive metal‐insulator‐semiconductor (MIS) device disclosed herein is the first example of technological exploitation of photoactive, red‐hair‐inspired biomaterials as soft enhancement layer for silicon in an optoelectronic device. The bio‐inspired materials described herein may provide the active component of new hybrid photocapacitive sensors with a chemically tunable response to visible light.     

Manipulating Bubbles in Aqueous Environment via a Lubricant‐Infused Slippery Surface

Designing functional interfaces to control solid/fluid interactions has emerged as an indispensable strategy for developing advanced materials and optimizing current technologies. Surfaces exhibiting special wettability offer many paradigms for regulating fluid behavior in practical applications including oil–water separation and fog harvesting. Nevertheless, the flexible manipulation of air bubbles under water still has room for further exploration. Here, it is reported that the lubricant‐infused slippery (LIS) surface with water repellency is applicable to manipulate bubbles in an aqueous environment. On the basis of the sufficient bubble adhesion, the shaped LIS tracks can be used in guiding the bubble delivery and facilitating continuous bubble distribution. Through the incorporation of an asymmetrical structure into the LIS surface, a triangle‐shaped bubble holder is capable of controlling a single bubble with ease. Moreover, the LIS surface is integrated with a H₂ microbubble evolving apparatus, demonstrating a potential method for in situ capture and delivery of microbubbles. The current finding reveals the meaningful interaction between underwater bubbles and the LIS surface, providing several examples for the applications of this bubble carrier, which should shed new light on the development of bubble‐controlling interfaces.     

Moisture Sensitive Smart Yarns and Textiles from Self‐Balanced Silk Fiber Muscles

Smart textiles that sense, interact, and adapt to environmental stimuli have provided exciting new opportunities for a variety of applications. However, current advances have largely remained at the research stage due to the high cost, complexity of manufacturing, and uncomfortableness of environment‐sensitive materials. In contrast, natural textile materials are more attractive for smart textiles due to their merits in terms of low cost and comfortability. Here, water fog and humidity‐driven torsional and tensile actuation of thermally set twisted, coiled, plied silk fibers, and weave textiles from these silk fibers are reported. When exposed to water fog, the torsional silk fiber provides a fully reversible torsional stroke of 547° mm^?1. Coiled‐and‐thermoset silk yarns provide a 70% contraction when the relative humidity is changed from 20% to 80%. Such an excellent actuation behavior originates from water absorption‐induced loss of hydrogen bonds within the silk proteins and the associated structural transformation, which are corroborated by atomistic and macroscopic characterization of silk and molecular dynamics simulations. With its large abundance, cost‐effectiveness, and comfortability for wearing, the silk muscles will open up additional possibilities in industrial applications, such as smart textiles and soft robotics.     

High‐Efficiency Water‐Transport Channels using the Synergistic Effect of a Hydrophilic Polymer and Graphene Oxide Laminates

Graphene oxide (GO) laminates possess unprecedented fast water‐transport channels. However, how to fully utilize these unique channels in order to maximize the separation properties of GO laminates remains a challenge. Here, a bio‐inspired membrane that couples an ultrathin surface water‐capturing polymeric layer (<10 nm) and GO laminates is designed. The proposed synergistic effect of highly enhanced water sorption from the polymeric layer and molecular channels from the GO laminates realizes fast and selective water transport through the integrated membrane. The prepared membrane exhibits highly selective water permeation with an excellent water flux of over 10 000 g m^?2 h^?1, which exceeds the performance upper bound of state‐of‐the‐art membranes for butanol dehydration. This bio‐inspired strategy demonstrated here opens the door to explore fast and selective channels derived from 2D or 3D materials for highly efficient molecular separation.     

Application‐layer community‐oriented uplink scheduler for CDMA networks

This paper focuses on community‐based mobile applications and delivers an efficient application‐layer uplink scheduler for the collection of community responses in CDMA networks, capable of pursuing the best possible compromise between delay and radio resource constraints. The scheduling problem is mathematically formulated and solved, based on a novel probabilistic approach inspired by the birthday paradox. Results of the proposed approach are presented and analyzed. Copyright © 2008 John Wiley & Sons, Ltd.