Nanowire Assemblies for Flexible Electronic Devices: Recent Advances and Perspectives

Advances in Flexible Magnetosensitive Materials and Devices for Wearable Electronics

Emerging fields, such as wearable electronics, digital healthcare, the Internet of Things, and humanoid robots, highlight the need for flexible devices capable of recording signals on curved surfaces and soft objects. In particular, flexible magnetosensitive devices garner significant attention owing to their ability to combine the advantages of flexible electronics and magnetoelectronic devices, such as reshaping capability, conformability, contactless sensing, and navigation capability. Several key challenges must be addressed to develop well-functional flexible magnetic devices. These include determining how to make magnetic materials flexible and even elastic, understanding how the physical properties of magnetic films change under external strain and stress, and designing and constructing flexible magnetosensitive devices. In recent years, significant progress is made in addressing these challenges. This study aims to provide a timely and comprehensive overview of the most recent developments in flexible magnetosensitive devices. This includes discussions on the fabrications and mechanical regulations of flexible magnetic materials, the principles and performances of flexible magnetic sensors, and their applications for wearable electronics. In addition, future development trends and challenges in this field are discussed.

Silver Nanowire Reinforced Conductive and Injectable Colloidal Gel for Effective Wound Healing Via Electrical Stimulation

The remarkable biocapacity, injectability, and adaptability of colloidal gels lead to their widespread use in tissue engineering as irregular defect implants. However, multifunctionalities including electroconductivity and antibacterial property are highly required for colloidal gels. In addition, the inherently weak mechanical property of physically crosslinked colloidal gels limits their application. Herein, Ag nanowires (Ag NWs)-reinforced colloidal gels composed of biocompatible gelatin nanoparticles and polydopamine-modified Ag NWs through the controlled electrostatic assembly, which are injectable and conductive, are presented. 1D Ag NWs can significantly improve the mechanical and electrical properties of the colloidal gel while maintaining its inherent excellent injectability. Owing to the network of Ag NWs, the storage modulus and conductivity of the optimized Ag NW colloidal gel are 7.5 and 13 times higher, respectively, than those of the colloidal gel made up of polydopamine-modified Ag nanoparticles with equivalent Ag concentration. Further, this Ag NW colloidal gel can adapt to sharp wounds on skin, which accelerates the healing of an MRSA-infected wound via electrical stimulation.

Ultrathin, High-Aspect-Ratio Bismuth Sulfohalide Nanowire Bundles for Solution-Processed Flexible Photodetectors

In this study, a novel synthesis of ultrathin, highly uniform colloidal bismuth sulfohalide (BiSX where X = Cl, Br, I) nanowires (NWs) and NW bundles (NBs) for room-temperature and solution-processed flexible photodetectors are presented. High-aspect-ratio bismuth sulfobromide (BiSBr) NWs are synthesized via a heat-up method using bismuth bromide and elemental S as precursors and 1-dodecanethiol as a solvent. Bundling of the BiSBr NWs occurs upon the addition of 1-octadecene as a co-solvent. The morphologies of the BiSBr NBs are easily tailored from sheaf-like structures to spherulite nanostructures by changing the solvent ratio. The optical bandgaps are modulated from 1.91 (BiSCl) and 1.88 eV (BiSBr) to 1.53 eV (BiSI) by changing the halide compositions. The optical bandgap of the ultrathin BiSBr NWs and NBs exhibits blueshift, whose origin is investigated through density functional theory-based first-principles calculations. Visible-light photodetectors are fabricated using BiSBr NWs and NBs via solution-based deposition followed by solid-state ligand exchanges. High photo-responsivities and external quantum efficiencies (EQE) are obtained for BiSBr NW and NB films even under strain, which offer a unique opportunity for the application of the novel BiSX NWs and NBs in flexible and environmentally friendly optoelectronic devices.

Replicating CD Nanogrooves onto PDMS to Guide Nanowire Growth for Monolithic Flexible Photodetectors with High Bending-Stable UV-vis-NIR Photoresponse

Guided nanowires grown on polymer surfaces facilitate their seamless integration as flexible devices without post-growth processing steps. However, this is challenging due to the inability of polymer films to provide the required lattice-matching effect. In this work, this challenge is addressed by replicating highly aligned nanogrooves from a compact disc (CD) onto a casted flexible polydimethylsiloxane (PDMS) surface. Leveraging the replicated nanogrooves, copper hexadecafluorophthalocyanine (F16CuPc) and various metal phthalocyanines are guided into large-area, self-aligned nanowires. Subsequently, by employing specifically designed shadow masks during electrode deposition, these nanowires are seamlessly integrated as either a monolithic flexible photodetector with a large sensing area or on-chip flexible photodetector arrays. The resulting flexible photodetectors exhibit millisecond and long-term stable response to UV-vis-NIR light. Notably, they demonstrate exceptional bending stability, retaining stable and sensitive photoresponse even at a curvature radius as low as 0.5 cm and after enduring 1000 bending cycles. Furthermore, the photodetector array showcases consistent sensitivity and response speed across the entire array. This work not only proves the viability of guided nanowire growth on flexible polymer surfaces by replicating CD nanogrooves but also underscores the potential for large-scale monolithic integration of guided nanowires as flexible devices.

Smart Energy Storage: W18O49 NW/Ti3C2Tx Composite-Enabled All Solid State Flexible Electrochromic Supercapacitors

Developing a highly efficient electrochromic energy storage device with sufficient color fluctuation and significant electrochemical performance is highly desirable for practical energy-saving applications. Here, to achieve a highly stable material with a large electrochemical storage capacity, a W18O49 NW/Ti3C2Tx composite has been fabricated and deposited on a pre-assembled Ag and W18O49 NW conductive network by Langmuir-Blodgett technique. The resulting hybrid electrode composed of 15 layers of W18O49 NW/Ti3C2Tx composite exhibits an areal capacitance of 125 mF cm-2, with a fast and reversible switching response. An optical modulation of 98.2% can be maintained at a current density of 5 mA cm-2. Using this electrode, a bifunctional symmetric electrochromic supercapacitor device having an energy density of 10.26 µWh cm-2 and a power density of 0.605 mW cm-2 is fabricated, with high capacity retention and full columbic efficiency over 4000 charge-discharge cycles. Meanwhile, the device displays remarkable electrochromic characteristics, including fast switching time (5 s for coloring and 7 s for bleaching), and a significant coloration efficiency of 116 cm2 C-1 with good optical modulation stability. In addition, the device exhibits significant mechanical flexibility and fast switching while being stable over 100 bending cycles, which is promising for real-world applications.

Stable and Tunable Quantum Conductance in Spider-Silk-like Synaptic Device for Neurocomputing

The quantum conductance (QC) behaviors in synaptic devices with stable and tunable conductance states are essential for high-density storage and brain-like neurocomputing (NC). In this work, inspired by the discontinuous transport of fluid in spider silk, a synaptic device composed of a silicon oxide nanowire network embedded with silicon quantum dots (Si-QDs@SiOx) is designed. The tunable QC behaviors are achieved in both the SET and RESET processes, and the QC states exhibit stable retention time exceeding 104 s in the synaptic device and show stable reproducibility after an interval of two months. The synaptic plasticity, including long-term potentiation/depression and Pavlovian conditioning function, is simulated based on the tunable conductance. The mechanism of stable and tunable QC behaviors is analyzed and clarified by beading effect of spider silk in Si-QDs@SiOx nanowires structure. The digit recognition capability of the device is evaluated by simulation using an artificial neural network consisting of the Si-QDs@SiOx-based synaptic device. These results provide insights into the development of neurocomputing systems with high classification accuracy.

A comprehensive review on the biomedical frontiers of nanowire applications

This comprehensive review examines the immense capacity of nanowires, nanostructures characterized by unbounded dimensions, to profoundly transform the field of biomedicine. Nanowires, which are created by combining several materials using techniques such as electrospinning and vapor deposition, possess distinct mechanical, optical, and electrical properties. As a result, they are well-suited for use in nanoscale electronic devices, drug delivery systems, chemical sensors, and other applications. The utilization of techniques such as the vapor-liquid-solid (VLS) approach and template-assisted approaches enables the achievement of precision in synthesis. This precision allows for the customization of characteristics, which in turn enables the capability of intracellular sensing and accurate drug administration. Nanowires exhibit potential in biomedical imaging, neural interfacing, and tissue engineering, despite obstacles related to biocompatibility and scalable manufacturing. They possess multifunctional capabilities that have the potential to greatly influence the intersection of nanotechnology and healthcare. Surmounting present obstacles has the potential to unleash the complete capabilities of nanowires, leading to significant improvements in diagnostics, biosensing, regenerative medicine, and next-generation point-of-care medicines.

Review on design strategies and applications of flexible cellulose‑carbon nanotube functional composites

Combining the excellent biocompatibility and mechanical flexibility of cellulose with the outstanding electrical, mechanical, optical and stability properties of carbon nanotubes (CNTs), cellulose-CNT composites have been extensively studied and applied to many flexible functional materials. In this review, we present advances in structural design strategies and various applications of cellulose-CNT composites. Firstly, the structural characteristics and corresponding treatments of cellulose and CNTs are analyzed, as are the potential interactions between the two to facilitate the formation of cellulose-CNT composites. Then, the design strategies and processing techniques of cellulose-CNT composites are discussed from the perspectives of cellulose fibers at the macroscopic scale (natural cotton, hemp, and other fibers; recycled cellulose fibers); nanocellulose at the micron scale (nanofibers, nanocrystals, etc.); and macromolecular chains at the molecular scale (cellulose solutions). Further, the applications of cellulose-CNT composites in various fields, such as flexible energy harvesting and storage devices, strain and humidity sensors, electrothermal devices, magnetic shielding, and photothermal conversion, are introduced. This review will help readers understand the design strategies of cellulose-CNT composites and develop potential high-performance applications.

Assembled one-dimensional nanowires for flexible electronic devices via printing and coating: Techniques, applications, and perspectives

The rapid progress in flexible electronic devices has necessitated continual research into nanomaterials, structural design, and fabrication processes. One-dimensional nanowires, characterized by their distinct structures and exceptional properties, are considered essential components for various flexible electronic devices. Considerable attention has been directed toward the assembly of nanowires, which presents significant advantages. Printing and coating techniques can be used to assemble nanowires in a relatively simple, efficient, and cost-competitive manner and exhibit potential for scale-up production in the foreseeable future. This review aims to provide an overview of nanowire assembly using printing and coating techniques, such as bar coating, spray coating, dip coating, blade coating, 3D printing, and so forth. The application of assembled nanowires in flexible electronic devices is subsequently discussed. Finally, further discussion is presented on the potential and challenges of flexible electronic devices based on assembled nanowires via printing and coating.

Interconnection Technologies for Flexible Electronics: Materials, Fabrications, and Applications

Flexible electronic devices require metal interconnects to facilitate the flow of electrical signals among the device components, ensuring its proper functionality. There are multiple factors to consider when designing metal interconnects for flexible electronics, including their conductivity, flexibility, reliability, and cost. This article provides an overview of recent endeavors to create flexible electronic devices through different metal interconnect approaches, with a focus on materials and structural aspects. Additionally, the article discusses emerging flexible applications, such as e-textiles and flexible batteries, as essential considerations.

Fully physical crosslinked BSA-based conductive hydrogels with high strength and fast self-recovery for human motion and wireless electrocardiogram sensing

The emergence of protein hydrogel sensors has attracted intensive attention because of their biocompatibility and biodegradability, and potential application in wearable electronics. However, natural protein hydrogel sensors commonly exhibited low conductivity, weak mechanical strength, and unsatisfactory self-recovery performance. Herein, a fully physical crosslinked conductive BSA-MA-PPy/P(AM-co-AA)/Fe³⁺ hydrogel based on methacrylic anhydride (MA)-modified and polypyrrole (PPy)-functionalized bovine serum albumin (BSA) introduced into poly(acrylamide-co-acrylic acid) (P(AM-co-AA)) matrix was constructed. Due to the presence of the hydrogen bond complexation and the metal-ligand coordination between ferric ion (Fe³⁺) and the polymer chain, the as-prepared hydrogel showed outstanding mechanical strength (5.36 MPa tensile stress, 17.66 MJ/m³ toughness, and 1.61 MPa elastic modulus) and fast self-recovery performance (99.89 %/96.18 %/93.57 % stress/elastic modulus/dissipated energy within 10 min at room temperature). Meanwhile, the hydrogel exhibited outstanding conductivity (1.13 S/m) due to the presence of PPy and Fe³⁺ moieties, high strain sensitivity (GF = 4.98) and good biocompatibility without causing skin allergic reactions. Thus, the hydrogel can be fabricated into strain sensor to monitor the joint motion of the human body. Moreover, it can be used as soft electrode in electrocardiogram device to realize wireless heart-rate monitoring in the real-time conditions (relaxation and post-exercising), which exhibited excellent reusability, stability, and reliability simultaneously.

Progress in Microtopography Optimization of Polymers-Based Pressure/Strain Sensors

Due to the wide application of wearable electronic devices in daily life, research into flexible electronics has become very attractive. Recently, various polymer-based sensors have emerged with great sensing performance and excellent extensibility. It is well known that different structural designs each confer their own unique, great impacts on the properties of materials. For polymer-based pressure/strain sensors, different structural designs determine different response-sensing mechanisms, thus showing their unique advantages and characteristics. This paper mainly focuses on polymer-based pressure-sensing materials applied in different microstructures and reviews their respective advantages. At the same time, polymer-based pressure sensors with different microstructures, including with respect to their working mechanisms, key parameters, and relevant operating ranges, are discussed in detail. According to the summary of its performance and mechanisms, different morphologies of microstructures can be designed for a sensor according to its performance characteristics and application scenario requirements, and the optimal structure can be adjusted by weighing and comparing sensor performances for the future. Finally, a conclusion and future perspectives are described.

Recent Advances and Challenges Toward Application of Fibers and Textiles in Integrated Photovoltaic Energy Storage Devices

Flexible microelectronic devices have seen an increasing trend toward development of miniaturized, portable, and integrated devices as wearable electronics which have the requirement for being light weight, small in dimension, and suppleness. Traditional three-dimensional (3D) and two-dimensional (2D) electronics gadgets fail to effectively comply with these necessities owing to their stiffness and large weights. Investigations have come up with a new family of one-dimensional (1D) flexible and fiber-based electronic devices (FBEDs) comprising power storage, energy-scavenging, implantable sensing, and flexible displays gadgets. However, development and manufacturing are still a challenge owing to their small radius, flexibility, low weight, weave ability and integration in textile electronics. This paper will provide a detailed review on the importance of substrates in electronic devices, intrinsic property requirements, fabrication classification and applications in energy harvesting, energy storage and other flexible electronic devices. Fiber- and textile-based electronic devices for bulk/scalable fabrications, encapsulation, and testing are reviewed and presented future research ideas to enhance the commercialization of these fiber-based electronics devices.

Flexible and Stretchable Carbon-Based Sensors and Actuators for Soft Robots

In recent years, the emergence of low-dimensional carbon-based materials, such as carbon dots, carbon nanotubes, and graphene, together with the advances in materials science, have greatly enriched the variety of flexible and stretchable electronic devices. Compared with conventional rigid devices, these soft robotic sensors and actuators exhibit remarkable advantages in terms of their biocompatibility, portability, power efficiency, and wearability, thus creating myriad possibilities of novel wearable and implantable tactile sensors, as well as micro-/nano-soft actuation systems. Interestingly, not only are carbon-based materials ideal constituents for photodetectors, gas, thermal, triboelectric sensors due to their geometry and extraordinary sensitivity to various external stimuli, but they also provide significantly more precise manipulation of the actuators than conventional centimeter-scale pneumatic and hydraulic robotic actuators, at a molecular level. In this review, we summarize recent progress on state-of-the-art flexible and stretchable carbon-based sensors and actuators that have creatively added to the development of biomedicine, nanoscience, materials science, as well as soft robotics. In the end, we propose the future potential of carbon-based materials for biomedical and soft robotic applications.

Fabrication and Thermal Performance of a Polymer-Based Flexible Oscillating Heat Pipe via 3D Printing Technology

As flexible electronic technologies rapidly developed with a requirement for multifunction, miniaturization, and high power density, effective thermal management has become an increasingly important issue. The oscillating heat pipe, as a promising technology, was used to dissipate high heat fluxes and had a wide range of applications. In this paper, we reported the fabrication and heat transfer performance evaluation of a polymer-based flexible oscillating heat pipe (FOHP) prepared using 3D printing technology. The 3D-printed inner surface presented excellent wettability to the working fluid, which was beneficial for the evaporation of the working fluid. Ethanol was selected as the working fluid, and the influence of the filling ratios range of 30-60% on heat transfer performance was analyzed. It was found that a 3D-printed FOHP with a filling ratio of 40% presented the best heat transfer performance with the lowest thermal resistance, and the fabricated heat pipes could be easily bent from 0° to 90°. With the best filling ratio, the thermal resistance of the FOHPs increased with larger bending angles. In addition, the 3D-printed FOHP was successfully applied for the thermal management of flexible printed circuits, and the results showed that the temperature of flexible printed circuits was kept within 72 °C, and its service life was guaranteed.

Continuous Patterning of Silver Nanowire-Polyvinylpyrrolidone Composite Transparent Conductive Film by a Roll-to-Roll Selective Calendering Process

The roll-to-roll (R2R) continuous patterning of silver nanowire-polyvinylpyrrolidone (Ag NW-PVP) composite transparent conductive film (cTCF) is demonstrated in this work by means of slot-die coating followed by selective calendering. The Ag NWs were synthesized by the polyol method, and adequately washed to leave an appropriate amount of PVP to act as a capping agent and dispersant. The as-coated Ag NW-PVP composite film had low electronic conductivity due to the lack of percolation path, which was greatly improved by the calendering process. Moreover, the dispersion of Ag NWs was analyzed with addition of PVP in terms of density and molecular weight. The excellent dispersion led to uniform distribution of Ag NWs in a cTCF. The continuous patterning was conducted using an embossed pattern roll to perform selective calendering. To evaluate the capability of the calendering process, various line widths and spacing patterns were investigated. The minimum pattern dimensions achievable were determined to be a line width of 0.1 mm and a line spacing of 1 mm. Finally, continuous patterning using selective calendering was applied to the fabrication of a flexible heater and a resistive touch sensing panel as flexible electronic devices to demonstrate its versatility.

All-atmospheric fabrication of Ag-Cu core-shell nanowire transparent electrodes with Haacke figure of merit >600 × 10-3 Ω-1

Transparent conducting electrodes (TCEs) are essential components in devices such as touch screens, smart windows, and photovoltaics. Metal nanowire networks are promising next-generation TCEs, but best-performing examples rely on expensive metal catalysts (palladium or platinum), vacuum processing, or transfer processes that cannot be scaled. This work demonstrates a metal nanowire TCE fabrication process that focuses on high performance and simple fabrication. Here we combined direct and plating metallization processes on electrospun nanowires. We first directly metallize silver nanowires using reactive silver ink. The silver catalyzes subsequent copper plating to produce Ag-Cu core-shell nanowires and eliminates nanowire junction resistances. The process allows for tunable transmission and sheet resistance properties by adjusting electrospinning and plating time. We demonstrate state-of-the-art, low-haze TCEs using an all-atmospheric process with sheet resistances of 0.33 Ω sq^-1 and visible light transmittances of 86% (including the substrate), leading to a Haacke figure of merit of 652 × 10^-3 Ω^-1. The core-shell nanowire electrode also demonstrates high chemical and bending durability.

Self-assembly, alignment, and patterning of metal nanowires

Armed with the merits of one-dimensional nanostructures (flexibility, high aspect ratio, and anisotropy) and metals (high conductivity, plasmonic properties, and catalytic activity), metal nanowires (MNWs) have stood out as a new class of nanomaterials in the last two decades. They are envisaged to expedite significantly and even revolutionize a broad spectrum of applications related to display, sensing, energy, plasmonics, photonics, and catalysis. Compared with disordered MNWs, well-organized MNWs would not only enhance the intrinsic physical and chemical properties, but also create new functions and sophisticated architectures of optoelectronic devices. This paper presents a comprehensive review of assembly strategies of MNWs, including self-assembly for specific structures, alignment for anisotropic constructions, and patterning for precise configurations. The technical processes, underlying mechanisms, performance indicators, and representative applications of these strategies are described and discussed to inspire further innovation in assembly techniques and guide the fabrication of optoelectrical devices. Finally, a perspective on the critical challenges and future opportunities of MNW assembly is provided.

Tough Adhesive, Antifreezing, and Antidrying Natural Globulin-Based Organohydrogels for Strain Sensors

Hydrogels are often used to fabricate strain sensors; however, they also suffer from freezing at low temperatures and become dry during long-time storage. Encapsulation of hydrogels with elastomers is one of the methods to solve these problems although the adhesion between hydrogels and elastomers is usually low. In this work, using bovine serum protein (BSA) as the natural globulin model and glycerol/H₂O as the mixture solvent, BSA/polyacrylamide organohydrogels (BSA/PAAm OHGs) were prepared by a facile photopolymerization approach. At the optimal condition, BSA/PAAm OHG demonstrated not only high toughness but also tough adhesion properties, which could strongly adhere to various substrates, such as glass, metals, rigid polymeric materials (even poly(tetrafluoroethylene), i.e., PTFE), and soft elastomers. Moreover, BSA/PAAm OHG was flexible and showed tough adhesion at -20 °C. The toughening mechanism and the adhesive mechanism were proposed. On being encapsulated by poly(dimethylsiloxane) (PDMS), it illustrated good antidrying performance. After introducing a conductive filler, the encapsulated BSA/PAAm OHG could be used as a strain sensor to detect human motions. This work provides a better understanding of the adhesive mechanism of natural protein-based organohydrogels.

Polymorphic Ga2S3 nanowires: phase-controlled growth and crystal structure calculations

The polymorphism of nanostructures is of paramount importance for many promising applications in high-performance nanodevices. We report the chemical vapor deposition synthesis of Ga₂S₃ nanowires (NWs) that show the consecutive phase transitions of monoclinic (M) → hexagonal (H) → wurtzite (W) → zinc blende (C) when lowering the growth temperature from 850 to 600 °C. At the highest temperature, single-crystalline NWs were grown in the thermodynamically stable M phase. Two types of H phase exhibited 1.8 nm periodic superlattice structures owing to the distinctively ordered Ga sites. They consisted of three rotational variants of the M phase along the growth direction ([001]_M = [0001]_H/W) but with different sequences in the variants. The phases shared the same crystallographic axis within the NWs, producing novel core-shell structures to illustrate the phase evolution. The relative stabilities of these phases were predicted using density functional theory calculations, and the results support the successive phase evolution. Photodetector devices based on the p-type M and H phase Ga₂S₃ NWs showed excellent UV photoresponse performance.

Manipulating Nanowire Structures for an Enhanced Broad-Band Flexible Photothermoelectric Photodetector

The photothermoelectric effect, directly converting light energy into electrical energy, shows promising prospects in self-powered broad-band optical detection, which can extend to various applications, such as sensing, optoelectronic communications, and wide-temperature-range measurements. However, the low photosensitivity, narrow-band response, and rapid performance degeneration under continuous illumination restrict its broad application. Herein, we propose a simple bottom-up strategy to manipulate nanowires (NWs) into a well-defined multilayer Te-Ag₂Te-Ag NW film, resulting in a high-performance photothermoelectric photodetector with a broad-band responsivity (4.1 V/W), large detectivity (944 MHz^1/2 W^-1), and fast response speed (0.4-0.7 s from 365 to 1200 nm). In addition, the ultrathin structure endows this device with slow and weak transverse heat conduction, enabling a stable voltage without an obvious degeneration over 1500 s. The highly anisotropic arrangement of NWs gives this device a prominent polarization sensitivity. Prospectively, this hierarchically designed nanowire film provides a promising pathway toward engineering photodetectors with high performance.

Highly Sensitive Piezoresistive Pressure Sensor Based on Super-Elastic 3D Buckling Carbon Nanofibers for Human Physiological Signals’ Monitoring

The three-dimensional (3D) carbon nanostructures/foams are commonly used as active materials for the high-performance flexible piezoresistive sensors due to their superior properties. However, the intrinsic brittleness and poor sensing properties of monolithic carbon material still limits its application. Rational design of the microstructure is an attractive approach to achieve piezoresistive material with superior mechanical and sensing properties, simultaneously. Herein, we introduce novel three-dimensional buckling carbon nanofibers (3D BCNFs) that feature a unique serpentine-buckling microstructure. The obtained 3D BCNFs exhibit superior mechanical properties, including super-elasticity (recovery speed up to 950 mm s⁻¹), excellent flexibility (multiple folds), high compressibility (compressed by 90%), and high fatigue resistance (10,000 bending cycles). The pressure sensor fabricated by the 3D BCNFs shows a high sensitivity of 714.4 kPa⁻¹, a fast response time of 23 ms, and a broad measuring range of 120 kPa. The pressure sensor is further applied to monitor the physiological signals of humans, and is capable of detecting the characteristic pulse waves from the radial artery, fingertip artery, and human-breath, respectively.

State of the art of ultra-thin gold layers: formation fundamentals and applications

Fabrication of ultra-thin gold (Au) layers (UTGLs) has been regarded as the key technique to achieve applications with tunable optical response, flexible sensors and electronic devices. Various strategies have been developed to optimize the wetting process of Au, resulting in the formation of UTGLs at a minimum thickness. The related studies on UTGLs attracted huge attention in recent years. On the one hand, the growth processes of UTGLs on different substrates were in-depth probed by advanced in situ characterization techniques and the effects of optimization strategies on the growth of UTGLs were also revealed. On the other hand, based on the understanding of the growth behavior and the assistance of optimization strategies, various applications of UTGLs were realized based on optical/plasmon responses, surface-enhanced Raman scattering and as electrodes for various sensors and electronic devices, as well as being seed layers for thin film growth. In this focused review, both the fundamental and practical studies on UTGLs in the most recent years are elaborated in detail. The growth processes of UTGLs revealed by in situ characterization techniques, such as grazing-incidence small-angle X-ray scattering (GISAXS), as well as the state of the art of UTGL-based applications, are reviewed.

Self-Assembly of Nanowires: From Dynamic Monitoring to Precision Control

ConspectusNatural biomaterials often show ordered nanowire structures (ONWS) which display unique structural color or superior mechanical performance. Meanwhile, plenty of modern nanodevices with ONWS have flourished with activities focused on both basic and applied research. Manipulating synthetic nanowire (NW) from a disordered state to a hierarchically ordered structure via various assembly strategies brings about intriguing and exotic chemical/physical properties. In the past decades, many methods have been developed to assemble NWs and fabricate organized architectures, such as Langmuir-Blodgett interfacial assembly, spin-coating assembly, fluid-flow-induced assembly, and ice-template assembly. Nevertheless, for practical applications, large-scale and high-efficiency assembly strategies toward precise controlled architectures are largely limited by the lack understanding of assembly mechanisms. Especially, the manipulation principles and driving forces behind the state-of-art assembly strategies are still unclear. Besides, the lesser research attention on dynamic kinetics also impedes the revelation of the NW self-assembly mechanism. With the emergence of advanced in situ techniques, such as synchrotron-based X-ray techniques and in situ transmission electron microscopy (TEM), the dynamic monitoring of NW behavior in many practical environments becomes possible. In addition, the alignment direction and the stacking manner of NW film are of significance to the final performance. There is a lack of connection between the properties of one-dimensional nanoscale building blocks and the functionalities of the macro-assembly structures. To this end, dynamic monitoring is highly desired, which enables the precision modulation of NW assembly structure, leading to the discovery or prediction of new structures, novel properties, and performance optimization.In this Account, we aim to uncover the underlying kinetics of NW assembly or local reaction and mass transportation processes, as well as to build a solid connection from individual NWs to NW assembly structures with enhanced properties and eventually to macroscopic materials application. We first review the recent progress in state-of-art NW assembly strategies for diverse aligned structures according to the manipulation principle and the driving forces. To systematically review the NW self-assembly strategies, we categorize these strategies into three states: NWs on the liquid interface via surface tension, NW assembly in liquid via solution-shearing flow field, and NW assembly at the solid interval via physical repulsive force. Then, we introduce the existing advanced characterization techniques, including synchrotron-based X-ray scattering and in situ TEM, to dynamically monitor the intermediate states of the NW assembly and transport processes. The comprehensive understanding of this thermodynamic and kinetic mechanism facilitates the rational design, large scale, and high-efficiency fabrication of NW assemblies, thus promoting their applications in tailored optical-electrical electronics, smart electrochromic devices, electrocatalysis, structural materials, and chiral photonic crystals.

LiNi0.5Mn1.5O4-Hybridized Gel Polymer Cathode and Gel Polymer Electrolyte Containing a Sulfolane-Based Highly Concentrated Electrolyte for the Fabrication of a 5 V Class of Flexible Lithium Batteries

The design and fabrication of lithium secondary batteries with a high energy density and shape flexibility are essential for flexible and wearable electronics. In this study, we fabricated a high-voltage (5 V class) flexible lithium polymer battery using a lithium nickel manganese oxide (LiNi0.5Mn1.5O4) cathode. A LiNi0.5Mn1.5O4-hybridized gel polymer cathode (GPC) and a gel polymer electrolyte (GPE) membrane, both containing a sulfolane (SL)-based highly concentrated electrolyte (HCE), enabled the fabrication of a polymer battery by simple lamination with a metallic lithium anode, where the injection of the electrolyte solution was not required. GPC with high flexibility has a hierarchically continuous three-dimensional porous architecture, which is advantageous for forming continuous ion-conduction paths. The GPE membrane has significant ionic conductivity enough for reliable capacity delivery. Therefore, the fabricated lithium polymer pouch cells demonstrated excellent capacity retention under continuous deformation conditions. This study provides a promising strategy for the fabrication of scalable and flexible 5 V class batteries using GPC and GPE containing SL-based HCE.

A New Strategy to Fabricate Nanoporous Gold and Its Application in Photodetector

Nanoporous gold (NPG) plays an important role in high-performance electronic devices, including sensors, electrocatalysis, and energy storage systems. However, the traditional fabricating methods of NPG, dealloying technique or electrochemical reduction technique, usually require complex experimental procedures and sophisticated equipment. In this work, we reported a unique and simple method to prepare the NPG through a low-temperature solution process. More importantly, the structure of the NPG-based electrode can be further controlled by using the post-treatment process, such as thermal treatment and plasma treatment. Additionally, we also demonstrate the application of the resulting NPG electrodes in flexible photodetectors, which performs a higher sensitivity than common planar photodetectors. We believe that our work opens a possibility for the nanoporous metal in future electronics that is flexible, large scale, with facile fabrication, and low cost.

Highly Stretchable High-Performance Silicon Nanowire Field Effect Transistors Integrated on Elastomer Substrates

Quasi-1D silicon nanowires (SiNWs) field effect transistors (FETs) integrated upon large-area elastomers are advantageous candidates for developing various high-performance stretchable electronics and displays. In this work, it is demonstrated that an orderly array of slim SiNW channels, with a diameter of <80 nm, can be precisely grown into desired locations via an in-plane solid-liquid-solid (IPSLS) mechanism, and reliably batch-transferred onto large area polydimethylsiloxane (PDMS) elastomers. Within an optimized discrete FETs-on-islands architecture, the SiNW-FETs can sustain large stretching strains up to 50% and repetitive testing for more than 1000 cycles (under 20% strain), while achieving a high hole carrier mobility, Ion /Ioff current ratio and subthreshold swing (SS) of ≈70 cm2 V-1 s-1 , >105  and 134 - 277 mV decade-1 , respectively, working stably in an ambient environment over 270 days without any passivation protection. These results indicate a promising new routine to batch-manufacture and integrate high-performance, scalable and stretchable SiNW-FET electronics that can work stably in harsh and large-strain environments, which is a key capability for future practical flexible display and wearable electronic applications.

Simple, Fast, and Scalable Reverse-Offset Printing of Micropatterned Copper Nanowire Electrodes with Sub-10 μm Resolution

Copper nanowires (CuNWs) possess key characteristics for realizing flexible transparent electronics. High-quality CuNW micropatterns with high resolution and uniform thickness are required to realize integrated transparent electronic devices. However, patterning high-aspect-ratio CuNWs is challenging because of their long length, exceeding the target pattern dimension. This work reports a novel reverse-offset printing technology that enables the sub-10 μm high-resolution micropatterning of CuNW transparent conducting electrodes (TCEs). The CuNW ink for reverse-offset printing was formulated to control viscoelasticity, cohesive force, and adhesion by adjusting the ligands, solvents, surface energy modifiers, and leveling additives. An inexpensive commercial adhesive handroller achieved a simple, fast, and scalable micropatterning of CuNW TCEs. Easy production of high-quality CuNW micropatterns with various curvatures and shapes was possible, regardless of the printing direction. The reverse-offset-printed CuNW micropatterns exhibited a minimum of 7 μm line width and excellent pattern qualities such as fine line spacing, sharp edge definition, and outstanding pattern uniformity. In addition, they exhibited excellent sheet resistance, high optical transparency, outstanding mechanical durability, and long-term stability. Flexible light-emitting diode (LED) circuits, transparent heaters, and organic LEDs (OLEDs) can be fabricated using high-resolution reverse-offset-printed CuNW micropatterns for applications in flexible transparent electronic devices.

Twin-Wire Networks for Zero Interconnect, High-Density 4-Wire Electrical Characterizations of Materials

Four-wire measurements have been introduced by Lord Kelvin in 1861 and have since become the standard technique for characterizing small resistances and impedances. However, high-density 4-wire measurements are generally complex, time-consuming, and inefficient because of constraints on interconnects, pads, external wires, and mechanical contacts, thus reducing reproducibility, statistical significance, and throughput. Here, we introduce, systematically design, analyze, and experimentally validate zero interconnect networks interfaced to external instrumentation by couples of twin wire. 3D-printed holders with magnets, interconnects, nonadhesive layers, and spacers can effortlessly establish excellent electrical connections with tunable or minimum contact forces and enable accurate measurements even for delicate devices, such as thin metals on soft polymers. As an example, we measured all the resistances of a twin-wire 29-resistor network made of silver-nanoparticle ink printed on polyimide, paper, or photo paper, including during sintering or temperature calibration, resulting in an unprecedentedly easy and accurate characterization of both resistivity and its temperature coefficient. The theoretical framework and experimental strategies reported here represent a breakthrough toward zero interconnect, simple, and efficient high-density 4-wire characterizations, can be generalized to other 4-wire measurements (impedances, sensors) and can open the way to more statistically meaningful and reproducible analyses of materials, high-throughput measurements, and minimally invasive characterizations of biomaterials.

Novel Two-Dimensional ABX3 Dirac Materials: Achieving a High-Speed Strain Sensor via a Self-Doping Effect

The pristine semimetal property of two-dimensional (2D) Dirac materials has limited their practical applications in today's electronic devices. Here we report a new type of 2D Dirac material, termed ABX₃ (A = F, Cl, Br, or I; B = P or As; X = C or Si) monolayers. We demonstrate that 14 ABX₃ monolayers possess good stability and high Fermi velocities. The FPC₃, ClPC₃, BrPC₃, and FAsC₃ monolayers exhibit a pristine n-type self-doping Dirac cone due to the interactions of electrons between the A-B units and C₆ rings, which is beneficial for realizing high-speed carriers. Interestingly, the ClPSi₃ monolayer exhibits remarkable responses to strain because a self-doping Dirac cone can be induced by relatively small in-plane biaxial strains (-5%), and the current-voltage (I-V) curves verified that the response strength is 11.57 times that of the graphene-based strain sensor at a bias of 1.10 V, indicating that the ClPSi₃ monolayer could be used as a potential excellent strain sensor.

Multifunctional Soft Robotic Finger Based on a Nanoscale Flexible Temperature-Pressure Tactile Sensor for Material Recognition

Robotic hands with tactile perception can perform more advanced and safer operations, such as material recognition. Nanowires with high sensitivity, fast response, and low power consumption are suitable for multifunctional flexible tactile sensors to provide the tactile perception of robotic hands. In this work, we designed a multifunctional soft robotic finger with a built-in nanoscale temperature-pressure tactile sensor for material recognition. The flexible multifunctional tactile sensor integrates a nanowire-based temperature sensor and a conductive sponge pressure sensor to measure the temperature change rate and contact pressure simultaneously. The developed nanoscale temperature and conductive sponge pressure sensor can reach a high sensitivity of 1.196%/°C and 13.29%/kPa, respectively. With this multifunctional tactile sensor, the soft finger can quickly recognize four metals within three contact pressure ranges and 13 materials within a high contact pressure range. By combining tactile information and artificial neural networks, the soft finger can recognize the materials precisely with a high recognition accuracy of 92.7 and 95.9%, respectively. This work proves the application potential of the multifunctional soft robot finger in material recognition.

Manipulating Nanowire Assemblies toward Multicolor Transparent Electrochromic Device

Assembling various nanowires together, enabling the assemblies with tailored optical, electrical, and multifunctional properties, represents a promising technology for next generation multifunctional electronics. Here we demonstrate a novel multicolor electrochromic device by coassembling W₁₈O₄₉ and V₂O₅ nanowires using solution-based Langmuir-Blodgett technique. The transparent W₁₈O₄₉ nanowire film became orange with the increasing addition of V₂O₅ nanowires and the film underwent a dynamic color change (orange, green, and gray) on application of different electrochemical biases of 2, 0, and -0.5 V (vs Ag/AgCl). Both the transmittance and color of the device can be easily controlled by manipulating the layers of coassembled nanowires and the ratios between the two nanowires. On the basis of this approach, different patterns can be easily fabricated with the addition of corresponding masks, and the solid electrochromic device is assembled, suggesting its significant potentials in smart windows and multicolor electrochromic displays.

An unprecedented polyoxometalate-based 1D double chain compound with opposite charges enables conductivity improvement

A POM-based one-dimensional (1D) chain compound, {BW₁₂O₄₀[Cu(2,2'-bipy)₂]₂[Cu(2,2'-bipy)(H₂O)]}{BW₁₂O₄₀[Cu(2,2'-bipy)₂][Cu(2,2'-bipy)(H₂O)₂]}·7H₂O, has been synthesized and structurally characterized, which represents an unprecedented 1D double chain structure with opposite charges. In contrast to common POMs, this compound exhibits a relatively high electrical conductivity of 1.17 × 10^-9 S cm^-1 at 25 °C. In addition, its semiconducting properties have also been investigated by application of photoelectrochemical sensing of H₂O₂.

Biomedical Implants with Charge-Transfer Monitoring and Regulating Abilities

Transmembrane charge (ion/electron) transfer is essential for maintaining cellular homeostasis and is involved in many biological processes, from protein synthesis to embryonic development in organisms. Designing implant devices that can detect or regulate cellular transmembrane charge transfer is expected to sense and modulate the behaviors of host cells and tissues. Thus, charge transfer can be regarded as a bridge connecting living systems and human-made implantable devices. This review describes the mode and mechanism of charge transfer between organisms and nonliving materials, and summarizes the strategies to endow implants with charge-transfer regulating or monitoring abilities. Furthermore, three major charge-transfer controlling systems, including wired, self-activated, and stimuli-responsive biomedical implants, as well as the design principles and pivotal materials are systematically elaborated. The clinical challenges and the prospects for future development of these implant devices are also discussed.

Stretchable Transparent Light-Emitting Diodes Based on InGaN/GaN Quantum Well Microwires and Carbon Nanotube Films

We propose and demonstrate both flexible and stretchable blue light-emitting diodes based on core/shell InGaN/GaN quantum well microwires embedded in polydimethylsiloxane membranes with strain-insensitive transparent electrodes involving single-walled carbon nanotubes. InGaN/GaN core-shell microwires were grown by metal-organic vapor phase epitaxy, encapsulated into a polydimethylsiloxane film, and then released from the growth substrate. The fabricated free-standing membrane of light-emitting diodes with contacts of single-walled carbon nanotube films can stand up to 20% stretching while maintaining efficient operation. Membrane-based LEDs show less than 15% degradation of electroluminescence intensity after 20 cycles of stretching thus opening an avenue for highly deformable inorganic devices.

Application-Driven Carbon Nanotube Functional Materials

Carbon nanotube functional materials (CNTFMs) represent an important research field in transforming nanoscience and nanotechnology into practical applications, with potential impact in a wide realm of science, technology, and engineering. In this review, we combine the state-of-the-art research activities of CNTFMs with the application prospect, to highlight critical issues and identify future challenges. We focus on macroscopic long fibers, thin films, and bulk sponges which are typical CNTFMs in different dimensions with distinct characteristics, and also cover a variety of derived composite/hierarchical materials. Critical issues related to their structures, properties, and applications as robust conductive skeletons or high-performance flexible electrodes in mechanical and electronic devices, advanced energy conversion and storage systems, and environmental areas have been discussed specifically. Finally, possible solutions and directions are proposed for overcoming current obstacles and promoting future efforts in the field.

Polarization-dependent optical band gap energy of aligned semiconducting titanium oxide nanowire deposits

Thin deposits of aligned semiconducting titanium oxide and of zinc oxide nanowires are prepared by grazing incidence spraying on transparent substrates. By measuring the transmittance of linearly polarized light of these anisotropic assemblies as compared to that of randomly oriented nanowires and of spherical nanoparticles, we find that titanium oxide nanowires exhibit an orientation-dependent variation of the apparent optical band gap energy at room temperature (>100 meV), depending on the direction of the polarization of the light with respect to the direction of alignment of the nanowires.

High-Performance Wearable Strain Sensor Based on MXene@Cotton Fabric with Network Structure

Flexible and comfortable wearable electronics are as a second skin for humans as they can collect the physiology of humans and show great application in health and fitness monitoring. MXene Ti₃C₂T_x have been used in flexible electronic devices for their unique properties such as high conductivity, excellent mechanical performance, flexibility, and good hydrophilicity, but less research has focused on MXene-based cotton fabric strain sensors. In this work, a high-performance wearable strain sensor composed of two-dimensional (2D) MXene d-Ti₃C₂T_x nanomaterials and cotton fabric is reported. Cotton fabrics were selected as substrate as they are comfortable textiles. As the active material in the sensor, MXene d-Ti₃C₂T_x exhibited an excellent conductivity and hydrophilicity and adhered well to the fabric fibers by electrostatic adsorption. The gauge factor of the MXene@cotton fabric strain sensor reached up to 4.11 within the strain range of 15%. Meanwhile, the sensor possessed high durability (>500 cycles) and a low strain detection limit of 0.3%. Finally, the encapsulated strain sensor was used to detect subtle or large body movements and exhibited a rapid response. This study shows that the MXene@cotton fabric strain sensor reported here have great potential for use in flexible, comfortable, and wearable devices for health monitoring and motion detection.

Janus membranes for membrane distillation: Recent advances and challenges

Membrane distillation (MD) is a promising hybrid thermal-membrane separation technology that can efficiently produce freshwater from seawater or contaminated wastewater. However, the relatively low flux and the presence of fouling or wetting agents in feed solution negate the applicability of MD for long term operation. In recent years, 'two-faced' membranes or Janus membranes have shown promising potential to decrease wetting and fouling problem of common MD system as well as enhance the flux performance. In this review, a comprehensive study was performed to investigate the various fabrication, modification, and novel design processes to prepare Janus membranes and discuss their performance in desalination and wastewater treatment utilizing MD. The promising potential, challenges and future prospects relating to the design and use of Janus membranes for MD are also tackled in this review.

A Powder Self-Healable Hydrogel Electrolyte for Flexible Hybrid Supercapacitors with High Energy Density and Sustainability

Ionic conductive hydrogel electrolyte is considered to be an ideal electrolyte candidate for flexible supercapacitor due to its flexibility and high conductivity. However, due to the lack of effective recycling methods, a large number of ineffective flexible hydrogel supercapacitors caused by some irreversible damages and dryness of hydrogel electrolyte are abandoned, which would induce heavy economic and environmental protection problems. Herein,a smart ionic conductive hydrogel (SPMA-Zn: ZnSO₄ /sodium alginate/polymethylacrylic acid) is developed for flexible hybrid supercapacitor (SPMA-ZHS). The SPMA-Zn exhibits an excellent self-healing ability and can recover its electrochemical performance after multiple mechanical damages. More importantly, it possesses an outstanding powder self-healable property, which could easily regenerate the hydrogel electrolyte after powdering, and maintain stable electrochemical performance of SPMA-ZHS. Besides, the SPMA-ZHS displays excellent electrochemical performance with a wide and stable working voltage range of 0-2.2 V, high energy density of 164.13 Wh kg^-1 at the power density of 1283.44 Wh kg^-1 and good stability with a capacity retention of 95.3% after 5000 charge/discharge cycles at 10 A g^-1 . The strategy in this work would provide a new insight in exploring flexible hydrogel electrolyte-based supercapacitor with good sustainability and high energy density for flexible wearable electronic devices.

Mechanical design of brush coating technology for the alignment of one-dimension nanomaterials

Widespread approaches to fabricate surfaces with aligned nanostructured topographies have been stimulated by opportunities to enhance interface performance by combing physical and chemical effects, in which brush-coating technology (BCT) is a cost-effective and feasible method for aligned film and large-scale production. Here, we reported a BCT process to realize the alignment of various 1D nanostructures through mechanical design that provides a more precise and higher shear force. By regulating the viscosity of dispersion, shear force is proved to be 24 and 20.3 times larger (when the volume ratio of water and glycerol is 1:3) according to the theoretical calculation and ANSYS simulating calculation results respectively, which plays a vital role in brush coating process. The universality was demonstrated by the alignment of one-dimension nanomaterials with different diameters, including silver nanowires (~80 nm), molybdenum trioxide nanobelts (~150 nm), vanadium pentoxide nanobelts (~150 nm) and bismuth sulfide nanobelts (~200 nm), et al., which in consequence have different alignment ratios. Meanwhile, anisotropic and flexible electrical conductors (the resistance anisotropic ratio was 2) and thermoelectric films (Seebeck coefficient was calculated to be 56.7 µV/K) were demonstrated.

Optically Programmable Plateau-Rayleigh Instability for High-Resolution and Scalable Morphology Manipulation of Silver Nanowires for Flexible Optoelectronics

The ability to engineer microscale and nanoscale morphology upon metal nanowires (NWs) has been essential to achieve new electronic and photonic functions. Here, this study reports an optically programmable Plateau-Rayleigh instability (PRI) to demonstrate a facile, scalable, and high-resolution morphology engineering of silver NWs (AgNWs) at temperatures <150 °C within 10 min. This has been accomplished by conjugating a photosensitive diphenyliodonium nitrate with AgNWs to modulate surface-atom diffusion. The conjugation is UV-decomposable and able to form a cladding of molten salt-like compounds, so that the PRI of the AgNWs can be optically programmed and triggered at a much lower temperature than the melting point of AgNWs. This PRI self-assembly technique can yield both various novel nanostructures from single NW and large-area microelectrodes from the NW network on various substrates, such as a nanoscale dot-dash chain and the microelectrode down to 5 μm in line width that is the highest resolution ever fabricated for the AgNW-based electrode. Finally, the patterned AgNWs as flexible transparent electrodes were demonstrated for a wearable CdS NW photodetector. This study provides a new paradigm for engineering metal micro-/nanostructures, which holds great potential in fabrication of various sophisticated devices.

Silicon-Au nanowire resonators for high-Q multiband near-infrared wave absorption

Semiconductors have been widely utilized to fabricate optoelectronic devices. Nevertheless, it is still a challenging task to achieve high-quality (Q) resonant light absorption using the high refractive index semiconductors. In this work, we propose a facile scheme for multi-band perfect absorption in the near-infrared range using an array of core-shell cylinder-shaped resonators which are composed of gold nanowires and thin silicon shells. Based on the cooperative effects between the photonic modes of the semiconductor cavity and the plasmonic resonances of the metal resonator, five sharp absorption peaks are observed with the maximal absorption close to 100% (99.98%) and a high Q factor up to 208. The multi-band sharp absorption is observed to be angle-insensitive and polarization-adjustable. Absorption efficiency can be quantitatively tuned via the polarization states following the classical Malus law. Moreover, different semiconductors such as gallium arsenide, indium arsenide, indium phosphide have been exploited to reproduce the sharp perfect absorption in this core-shell resonators platform. The remarkable features make the proposed system potential for multiple applications such as multispectral filtering, photo-detection and hot electron generation.

Self-Assembly Anisotropic Magnetic Nanowire Films Induced by External Magnetic Field

Self-assembly generated materials induced by an external magnetic field have attracted considerable interest following the development of nanodevices. However, the fabrication of macroscopic and anisotropic magnetic films at the nanoscale remains a challenge. Here, anisotropic magnetic films are successfully prepared using a solution-based nanowire assembly strategy under a magnetic field. The assembly process is manipulated by changing the thickness of silica shell coated on the surface of magnetic nanowires. The anisotropic magnetic films show highly anisotropic magnetization under different angles of magnetic field and better magnetization properties than that of disordered magnetic films. The well-defined nanowire arrays enable magnetization anisotropic property which may be useful in the magnetic energy conversion technologies and biomedical sciences which lie far beyond those achievable with traditional magnetic materials.

Radial Nanowire Assemblies under Rotating Magnetic Field Enabled Efficient Charge Separation

Developing efficient charge separation strategies is essential to achieve high-power conversion efficiency in the fields of chemistry, biology, and material science. Herein, we develop a facile strategy for fabrication of unique wafer-scale radial nanowire assemblies by exploiting shear force in rotary solution. The assembly mechanism can be well revealed by the large-scale stochastic dynamics simulation. Free electrons can be rapidly generated to produce quantitatively tunable current output when the radial nanowire assemblies rotate under the magnetic field. Moreover, the photoconductive performance of the radial semiconductor nanowire assemblies can be remarkably enhanced as the electron-hole recombination was retrained by the efficient charge separation under the rotating magnetic field. Such large-scale unique nanowire assemblies will facilitate the design of an efficient charge separation process in biosystem, sensors, and photocatalysis.