Nanowire Mesh Research Articles

One-Dimensional ZnO Nanorod Array Grown on Ag Nanowire Mesh/ZnO Composite Seed Layer for H2 Gas Sensing and UV Detection Applications.

Photodetectors and gas sensors are vital in modern technology, spanning from environmental monitoring to biomedical diagnostics. This paper explores the UV detection and gas sensing properties of a zinc oxide (ZnO) nanorod array (ZNA) grown on silver nanowire mesh (AgNM) using a hydrothermal method. We examined the impact of different zinc acetate precursor concentrations on their properties. Results show the AgNM forms a network with high transparency (79%) and low sheet resistance (7.23 Ω/□). A sol-gel ZnO thin film was coated on this mesh, providing a seed layer with a hexagonal wurtzite structure. Increasing the precursor concentration alters the diameter, length, and area density of ZNAs, affecting their performance. The ZNA-AgNM-based photodetector shows enhanced dark current and photocurrent with increasing precursor concentration, achieving a maximum photoresponsivity of 114 A/W at 374 nm and a detectivity of 6.37 × 1014 Jones at 0.05 M zinc acetate. For gas sensing, the resistance of ZNA-AgNM-based sensors decreases with temperature, with the best hydrogen response (2.71) at 300 °C and 0.04 M precursor concentration. These findings highlight the potential of ZNA-AgNM for high-performance UV photodetectors and hydrogen gas sensors, offering an alternative way for the development of future sensing devices with enhanced performance and functionality.

Gold nanowire mesh electrode for electromechanical device

Ionic polymer-metal composite (IPMC) actuators were prepared with Nafion film as the ionic polymer and gold nanowire (Au-NW) mesh film as the metal electrodes by hot-pressing, which shortened preparation time within 1 h. As a reference, IPMC actuator consisting of Nafion film and gold foil (Au-foil) was also prepared. Au-NW mesh film can be an electrode with thinner (about 150 nm) and lower surface resistivity (about 0.5 Ω sq−1) than the conventional electrode prepared by electroless plating. Larger contact area of the Au-NW mesh electrode than the Au-foil electrode resulted in better actuation performance (60% larger peak-to-peak displacement in actuation). It was confirmed that the transformation behavior of Au-NWs differed depending on the external stimuli condition. Namely Au-NWs transformed to Au nanoparticles in the case of the heat stimulus only. Meanwhile, Au-NWs transformed to plates in the case of the heat and pressure stimuli. While higher temperature improved the adhesion of Au-NW mesh electrode to the Nafion surface, it induced the transformation of nanowire to plates. The IPMC actuator that the Au-NW mesh electrodes were hot-pressed at 90 ºC exhibited the highest capacitance and the largest peak-to-peak displacement in actuation. This research expanded the application field of gold nanowires to the electromechanical devices.

Enhancing the memristive effects in SnO2 nanowire networks

We present a study of SnO2 nanowire network acting as a resistive memory device. Charge transport features in these devices were controlled by modulating the behavior of the energy barriers of nanowire-nanowire interfaces and the Schottky barrier under the electrodes. Both barriers were found to be affected by the distribution and availability of charges along the nanowires mesh and in the surrounding atmosphere. The consequent memristive effect was dependent of the environment conditions but also controllable by managing the availability of charges for the transport properties. Using a polymeric barrier layer to avoid the direct contact of nanowires with the surrounding atmosphere proved to be an effective method to obtain reliable/better results after many memristive cycles. This simple procedure of polymeric coating offers some benefits such a more stable gain and a ON/OFF ratio improvement (from 1.55 to 3.60). Furthermore, coated devices showed potential features for use in synaptic learning applications.

Ultra-stable and tough bioinspired crack-based tactile sensor for small legged robots

For legged robots, collecting tactile information is essential for stable posture and efficient gait. However, mounting sensors on small robots weighing less than 1 kg remain challenges in terms of the sensor’s durability, flexibility, sensitivity, and size. Crack-based sensors featuring ultra-sensitivity, small-size, and flexibility could be a promising candidate, but performance degradation due to crack growing by repeated use is a stumbling block. This paper presents an ultra-stable and tough bio-inspired crack-based sensor by controlling the crack depth using silver nanowire (Ag NW) mesh as a crack stop layer. The Ag NW mesh inspired by skin collagen structure effectively mitigated crack propagation. The sensor was very thin, lightweight, sensitive, and ultra-durable that maintains its sensitivity during 200,000 cycles of 0.5% strain. We demonstrate sensor’s feasibility by implementing the tactile sensation to bio-inspired robots, and propose statistical and deep learning-based analysis methods which successfully distinguished terrain type.

Modulation of Early Stage Neuronal Outgrowth through Out-of-Plane Graphene.

The correct wiring of a neural network requires neuron to integrate an incredible repertoire of cues found in their extracellular environment. The astonishing efficiency of this process plays a pivotal role in the correct wiring of the brain during development and axon regeneration. Biologically inspired micro- and nanostructured substrates have been shown to regulate axonal outgrowth. In parallel, several studies investigated graphene's potential as a conductive neural interface, able to enhance cell adhesion, neurite sprouting and outgrowth. Here, we engineered a 3D single- to few-layer fuzzy graphene morphology (3DFG), 3DFG on a collapsed Si nanowire (SiNW) mesh template (NT-3DFGc), and 3DFG on a noncollapsed SiNW mesh template (NT-3DFGnc) as neural-instructive materials. The micrometric protruding features of the NWs templates dictated neuronal growth cone establishment, as well as influencing axon elongation and branching. Furthermore, neurons-to-graphene coupling was investigated with comprehensive view of integrin-mediated contact adhesion points and plasma membrane curvature processes.

SiC Nanowire Mesh in High-Porosity Silicon Foam for Enhanced Electromagnetic Wave Absorption

SiC Nanowire Mesh in High-Porosity Silicon Foam for Enhanced Electromagnetic Wave Absorption

Internal Mass Transport Induced Voltage Losses during Water Electrolysis on Interconnected Nickel Nanowire Mesh Electrodes

Nickel nanowire mesh electrodes offer great potential for water electrolysis in alkaline environment, given their high internal surface area, mechanical strength, and alkaline resistance. Here we use a nickel nanowire mesh with a specific area of 26 m2/cm3, resulting in ~100-fold area enhancement for a 4µm thick nanowire mesh, compared to planar nickel. This highly benefits geometric current density, potentially into a regime where mass transport is the main limiting factor. Therefore, we performed a systematic study of electrode behaviour under various mass transport conditions to decouple kinetic and mass transfer related contributions to electrode voltage losses.An electrochemical flow cell was designed to measure the nanowire mesh electrode performance under optimal mass transport conditions. The cell provided electrolyte flow through the nanomesh, enabling convective supply of reagent into the nanopores as well as convective removal of reaction products. Facilitated by the inherent strength of the nanowire mesh, superficial flow velocities up to 1 cm/s could be obtained, with which geometric current densities as high as 320 mA/cm2 could be measured in the kinetically limited (flowrate independent) regime.Internal mass transport limitations were isolated by use of an inverted rotating disk electrode (iRDE). Koutecky-Levich analysis was performed to compensate for external mass transfer contributions on both nanowire mesh electrodes and planar electrodes. The nanowire mesh as iRDE resembles operating conditions in an electrolyzer, whereas the planar electrode provides a well-defined benchmark area for the electrode surface activity.For both the oxygen evolution reaction as the hydrogen evolution reaction, mass transport limitations were studies as function of current density and electrolyte (NaOH) concentration. Nanowire mesh electrode operation in the presence of internal mass transport limitations was compared to the non-limited condition and planar benchmark, from which the electrode effectiveness factor could be calculated. A 1-d simplified model of the electrode was used to explain the observed phenomena and to provide guidance for design optimization.

Stretchable and Directly Patternable Double-Layer Structure Electrodes with Complete Coverage

Stretchable electrodes are widely used in next-generation wearable electronics. Recent studies incorporated designs that help rigid electrodes attain stretchability. However, these structures exhibited unsatisfactory charge/signal extraction efficiency because of their low areal fill factor. Additionally, they cannot be photolithographically patterned on polymer substrates because of their low adhesion, requiring additional complicated fabrication steps. We developed photolithographically patternable stretchable electrodes with complete coverage and enhanced charge-extraction efficiency. The electrodes, comprising double layers, included a chemically treated Ag nanowire mesh and Au thin film. The interfacial linker role of polyvinylpyrrolidone chemically strengthened the interfacial bonds, and the reinforced concrete structure of nanowire-embedded metal thin films enhanced the mechanical properties. Therefore, the electrodes provided superior efficiency and stability in capturing physical, electromagnetic, and electrophysiological signals while exceeding the existing stretchable electrode limits. A broad range of applications are foreseen, such as electrocardiogram sensing electrodes, strain sensors, temperature sensors, and antennas.

Cascading Photoelectric Detecting and Chemiresistive Gas-Sensing Properties of Pb5 S2 I6 Nanowire Mesh for Multi-Factor Accurate Fire Alarm.

Accurate fire warning is very important for people's life and property safety. The most commonly used fire alarm is based on the detection of a single factor of gases, smoke particles, or temperature, which easily causes false alarm due to complex environmental conditions. A facile multi-factor route for fabricating an accurate analog fire alarm using a Pb5 S2 I6 nanowire mesh based on its photoelectric and gas-sensing dual function is presented. The Pb5 S2 I6 nanowire mesh presents excellent photoelectric detection capabilities and is sensitive to ppm-level NO2 at room temperature. Under the "two-step verification" circuit of light and gas factors, the bimodal simulation fire alarm based on this Pb5 S2 I6 nanowire mesh can resist the interference of complex environmental factors and effectively reduce the false alarm rate.

Nanoscale Electrical Investigation of Transparent Conductive Electrodes Based on Silver Nanowire Network (Adv. Mater. Interfaces 18/2022)

Nanoscale Electrical Investigation of Transparent Conductive Electrodes In article number 2200019, Sy Hieu Pham, Philippe Leclère, and co-workers analyze at the nanoscale the current percolation mechanisms through a silver nanowire mesh. This network is successfully used for transparent and flexible electrodes in organic and hybrid electronic devices with excellent Figure of Merit compared to classical electrodes. High current pathways (light blue) and intermediate conductive and nonconductive nanowires (orange and purple, respectively) are shown.

Freestanding silicon nanowires mesh for efficient electricity generation from evaporation-induced water capillary flow

Scavenging energy stored at the water/solid interface into electrical power by the natural water evaporation process provides a promising method to supply sustainable electricity for self-powered electronics. The main barriers constraining its applications are the limited materials availability and ambiguous underlying mechanisms, detrimental to the improvement of output power. Herein, we report a highly flexible and efficient evaporation-induced electricity generator (EIEG) that dexterously exploits the directional water capillary flow inside the silicon nanowires (SiNWs) mesh nanopores. Benefiting from the large surface/volume ratio and high surface potential of nanostructured SiNWs mesh film, an EIEG continuously delivers a high open-circuit voltage of ~1.5 V and a maximum power density of over 160 μW·cm−3, which surpasses the analogous flexible EIEGs. Moreover, the correlation between the output power and capillary flow direction, diffusion length, and velocity as well as the species and ionic strength of various liquids have been systematically explored to identify the mechanism underlying the power generation. This study not only provides an in-depth understanding of water/solid interactions but also spikes a green technique to fabricate flexible generators that tap energy from the copious water reservoir.

Metal nanowires grown in situ on polymeric fibres for electronic textiles.

A key aspect of the use of conventional fabrics as smart textiles and wearable electronics is to incorporate a means of electrical conductivity into single polymer fibres. We present the transformation of thin polymer fibres and fabrics into conductive materials by in situ growth of a thin, optically transparent gold–silver nanowire (NW) mesh with a relatively low metal loading directly on the surface of polymer fibres. Demonstrating the method on poly(lactic-co-glycolic) acid and nylon microfibres, we show that the NW network morphology depends on the diameter of the polymer fibres, where at small diameters (1–2 μm), the NWs form a randomly oriented network, but for diameters above several micrometers, the NWs wrap around the fibres transversally. This phenomenon is associated with the stiffness of the surfactant templates used for the NW formation. The NW-decorated fibres exhibit a significant increase in conductivity. Moreover, single fibres can be stretched up to ∼15% before losing the electrical conductivity, while non-woven meshes could be stretched by about 25% before losing the conductivity. We believe that the approach demonstrated here can be extended to other polymeric fibres and that these flexible and transparent metal-coated polymer fibres could be useful for various smart electronic textile applications.

PROFITABLE WASTE OIL BURNINGSYSTEM

By autonomously navigating the water's surface, Sea swarm proposes a new system for ocean-skimming andoil removal. Sea swarm uses a photovoltaic-powered conveyor belt made of a thin nanowire mesh to propel itself and collect oil. The nanomaterial, patented at MIT, can absorb up to 20 timesits weightin oil. The flexible conveyor beltsoftly rolls over the ocean'ssurface, absorbing oil while deflecting water because of its hydrophobic properties Sea swarm is meant to figure as a fleet, or “swarm” of vehicles, which communicate their location through GPS and Wi-Fi so as to make an organized system for collection that can work continuously without human support. Sea swarm works by detecting the sting of a spill and moving inward until it's removed the oilfromone site before joining other vehicles that are still cleaning. The fleet uses cuttingedge nanotechnology to unravel current environmental problems while envisioning long-term solutions for the longer term. With a replacement design strategy, we will revive and preserve the standard of our oceans.

A universal robust bottom-up approach to engineer Greta-oto-inspired anti-reflective structure

The Greta oto butterfly has transparent wings with extraordinary omnidirectional anti-reflection behavior, owing to unusual nanostructures with random height and pitch/space distribution on its wing surface. The beauty and efficacy of such nanostructures are proven designs but difficult to reproduce en masse. Here, we establish a low-cost bottom-up approach by simply stacking monolayer-aligned agitation-assisted deposition of silver nanowire (AgNW) meshes followed by deposition of various overcoats. Such AgNW meshes provide the template to grow nanostructures, imitating those on the Greta oto’s wings that consist of randomly situated nanocones with controllable mean pitches and heights. The resulting nanostructure enhances anti-reflections in both SiO2/AgNW and VO2/AgNW systems, which showed reduced omnidirectional reflectance up to 33% and 70%, respectively. Furthermore, the VO2/AgNW system exhibits enhanced luminous and infrared transmittance without sacrificing solar modulation. Our robust bottom-up approach provides a simpler alternate non-lithographic way to economically produce controlled biomimetic anti-reflective nanostructured coatings.

Moisture-Assisted Formation of High-Quality Silver Nanowire Transparent Conductive Films with Low Junction Resistance

Silver nanowire (AgNWs) transparent conductive film (TCF) is considered to be the most favorable material to replace indium tin oxide (ITO) as the next-generation transparent conductive film. However, the disadvantages of AgNWs, such as easy oxidation and high wire-wire junction resistance, dramatically limit its commercial application. In this paper, moisture treatment was adopted, and water was dripped on the surface of AgNWs film or breathed on the surface so that the surface was covered with a layer of water vapor. The morphology of silver nanowire mesh nodes is complex, and the curvature is large. According to the capillary condensation theory, water molecules preferentially condense near the geometric surface with significant curvature. The capillary force is generated, making the wire-wire junction of AgNWs mesh bond tightly, resulting in good ohmic contact. The experimental results show that AgNWs-TCF treated by moisture has better conductivity, with an average sheet resistance of 20 Ω/sq and more uniform electrical properties. The bending test and adhesion test showed that AgNWs-TCF treated by moisture still exhibited good mechanical bending resistance and environmental stability.

(Invited) Bioelectronics with Nanocarbons

We focus on developing a new class of nanoscale materials for the investigation of biological entities at multiple length scales, from the molecular level to complex cellular networks. Our highly flexible bottom-up nanomaterials synthesis capabilities allow us to form unique hybrid-nanomaterials. Recently, we have demonstrated highly controlled synthesis of 3D out-of-plane single- to few-layer fuzzy graphene (3DFG) on a Si nanowire (SiNW) mesh template. By varying graphene growth conditions, we control the size, density, and electrical properties of the NW templated 3DFG (NT-3DFG). This flexible synthesis inspires formation of complex hybrid-nanomaterials with tailored optical and electrical properties to be used in biosensing, and energy-related research. The exceptional synthetic control and flexible assembly of nanomaterials provide powerful tools for fundamental studies and applications in life science and open up the potential to seamlessly merge either nanomaterials-based platforms or unique nanosensor geometries and topologies with cells, fusing nonliving and living systems together.

Freestanding Silicon Nanowires Mesh for Efficient Electricity Generation from Evaporation-Induced Water Capillary Flow

Freestanding Silicon Nanowires Mesh for Efficient Electricity Generation from Evaporation-Induced Water Capillary Flow

Characterization of the Coupling between Out‐of‐Plane Graphene and Electrogenic Cells

AbstractThe cell‐chip coupling is in general regulated by the interplay between cells and the material surface at the interface. Electroactive planar materials have shown limited crosstalk with cells, whereas pseudo 3D patterned materials promote a more intimate contact with the biological system. Here, unprecedented physical properties of a carbon‐based material, i.e., graphene, to engineer out‐of‐plane morphologies are exploited: 1) 3D single‐ to few‐layer fuzzy graphene morphology (3DFG), 2) 3DFG on a collapsed Si nanowire mesh template, and 3) 3DFG on a noncollapsed Si nanowire mesh template. These materials are synthesized and interfaced with cardiomyocyte‐like cells focusing on the characterization of the cytoskeletal arrangement as well as membrane wrapping processes yet regulated by endocytic proteins. Finally, some major conditions to promote tight coupling to the device and eventually spontaneous intracellular penetration are found.

Visualizing and Analyzing 3D Metal Nanowire Networks for Stretchable Electronics

AbstractComposites based on conductive nanowires embedded in elastomers are popular in a wide range of stretchable electronics applications where the requirements are either a stable or a highly increasing electrical resistance upon strain. Despite the widespread use of such composites, their production is not based in solid theoretical grounds but rather in empirical observations. The lack of such a framework is due to limitations in the methods for studying nanowire meshes, in particular the lack of knowledge on the spatial distribution of the nanowires and the change of their position under strain. This hurdle is overcome by collecting 3D reconstructed X‐ray tomographies of silver nanowires embedded in polydimethylsiloxane (PDMS) under variable deformations and the missing structural information of the nanomaterial is obtained by unsupervised artificial intelligence image analysis. This allowed to reveal the precise assembly mechanisms of nanowire systems and derive a precise analytical formula for the piezoresistive response of the composite and finally to simulate the behavior of arbitrary samples in‐silico.

Geometrical optimization for silver nanowire mesh as a flexible transparent conductive electrode.

We report the effect of the geometric parameters on transparency and conductivity in a metallic nanowire mesh as a transparent electrode. Today, indium tin oxide and fluorine-doped tin oxide are used as the transparent electrode for displays and solar cells. Still, there is a definite need for their replacement due to drawbacks such as brittleness, scarcity, and adverse environmental effects. Metallic nanowire mesh is likely the best replacement option, but the main issue is how to find the optimal structure and how to get the best performance. Since the interaction of light with nanowire mesh is complicated, there is no straightforward rule with a simple analytical solution. We developed a kit based on wave optics for calculating the optical transmission of metallic nanowire mesh, which, unlike previous works, includes the interaction of light with the nanowire mesh, such as localized surface plasmon resonance (LSPR), surface plasmon polariton (SPP), and Rayleigh anomaly (RA). So, it is possible to accurately predict the effect of these phenomena and the transmission of mesh. Using the mentioned kit, we will be able to investigate the different geometrical structures of meshes to achieve optimal geometry. This kit is based on the classical Maxwell theory and empirical data and uses finite-difference time-domain for solving equations and experiential results for validation. Comparing the results by a redefined figure of merit shows that LSPR has the most significant reduction on transparency, whereas increasing the thickness (t) to width (w) ratio of the nanowire in the metallic mesh can reduce the LSPR effect and/or shifts it to the invisible region. The wire pitch (p) has no tangible impact on LSPR, but p can be chosen higher than 700 or lower than 350 nm to remove the extinction effects of the first-order RA. If p was larger than 150 nm, SPP could appear in the visible region of the spectrum. In small p, lower modes of SPP with higher intensities occur; therefore, there is an optimum value for p around 300 nm. The reduction of t and w reduces the intensity of SPP and causes it to red shift. By comparing the 900 different structures, the highest figure of merit is obtained in a p of 300 nm with a minimum w (10 nm) and maximum t (100 nm).