Nanowire Networks Research Articles

Significantly improved thermal conductivity of C/C composite by constructing 3D SiC nanowires network in carbon felt via vacuum thermal evaporation

Developing a nanoscale secondary thermal conduction network within carbon fiber performs is a challenging yet effective method to substantially enhance the thermal conductivity of C/C composites. In this study, a strategy for creating a three-dimensional (3D) SiC nanowires (SiCNWs) thermal conductivity network in carbon felts (CFs) was implemented using vacuum thermal evaporation technology to fabricate SiCNWs modified C/C composites (SiCNW–C/C). The growth mechanism of SiC nanowires within CFs and their impact on the microstructure and thermal conductivity of the C/C composite were thoroughly investigated. The findings indicate that a SiC nanowires thermal conduction network can be successfully established within carbon felts without catalysts by initiating nucleation sites and managing reaction pressure. An appropriate reaction pressure is crucial not only for the uniform growth of SiC nanowires but also as a key factor in modulating the content and microstructure of the SiC nanowires. SiC nanowires prepared at 150 Pa exhibit minimal structural defects and are evenly distributed throughout the carbon felts, markedly enhancing the thermal response rate of the felts. The thermal conductivity of these SiCNW-modified C/C composites, both parallel and perpendicular to the carbon fibers, increased to 173 W/m•K and 112 W/m•K, respectively, approximately tripling that of the pure C/C composite. The exceptional thermal management capabilities of SiCNW–C/C were empirically validated through simulated operational chips and finite element simulation. This work presents an effective approach for producing C/C composite with high thermal conductivity particularly through the thickness, offering promising applications in the thermal management of advanced electronics.

Controlled Assembly of Nanowires into Welded Nanowire Networks for Memristor Device Fabrication

Next-generation electronic devices are essential for neuromorphic computing (or brain-inspired computing), which is essential for the high-speed processing of big data using artificial intelligence tools.(1) Memristors, an important constituent of these next-generation electronic devices, have been fabricated using many forms of metal oxides, including nanowires. Nanowires forms of oxides, although reduce the complexity of the memristive device fabrication process, need many technological advances for their widespread use in memristor fabrication.(1) For instance, the cyclability of devices needs to be improved. Furthermore, realizing the high density of nanowire-based memristor devices requires methods for addressing individual nanowires in large assemblies (i.e., arrays) of nanowires, strategies for which also need to be developed.(1) A possible avenue to address these problems is through the use of nanowire networks,(1) specifically those that have nanowires welded together via bridges that have the same chemical composition as those of the nanowires themselves.(2) In this configuration, the resistive switching of both the nanowires and the randomly-formed junctions between the nanowires can be employed to make mesoscale devices, circumventing the need to individually address each nanowire in the nanowire assemblies.(1) Realizing memristive devices based on welded nanowire networks, therefore, requires a strategy for assembly via welding of pre-synthesized nanowires into networks that offer the ability to control the chemical compositions of the interfaces between the nanowires and the densities of nanowires within the assemblies.(2, 3) In the presentation, strategies developed by our group for the assembly of semiconductor nanowires into welded nanowire networks of controlled densities will be discussed in detail. Specific devices that will be discussed include assembly via welding of Mg2Si, TiO2 and TiC nanowires.(2, 3) The assembly via welding of nanowires into networks is expected to accelerate the testing of mesoscale memristive devices, irrespective of the method employed for the synthesis of the nanowires used in the assemblies. This is expected to aid in accelerating both the science and technology needed for the deployment of memristive devices.

Effect of Voids on the Percolation Conductivity of Carbon Nanotube Networks

Two-dimensional (2D) networks consisting of one-dimensional (1D) wires, such as carbon nanotubes, metal nanowires, and graphene nanoribbons, are promising candidates for next-generation flexible transparent conducting electrodes in devices such as organic light-emitting diodes (OLEDs), solar cells, touch screens, smart windows, transparent heaters, and liquid crystal displays. Nanotube networks also have broad application potential in flexible electronics, such as thin film transistors, wearables, electronic skin, and internet of things (IoT) sensors.The electrical conductivity of carbon nanotube networks is governed by percolation, which deals with the formation of long-range connectivity in random networks. As a result, Monte Carlo simulations need to be employed in order to compute the electrical properties of these networks [1,2]. Understanding the impact of voids, which could be present due to lack of control in the deposition process or introduced intentionally, on the percolation conductivity of carbon nanotube networks is critical for applications such as transparent conductive electrodes, thin film transistors, sensing, and hardware security.In this work, we generate two-dimensional square carbon nanotube networks with square voids located at the center of the nanotube network. We define the relative void size as the ratio of the length of the side of the void to the length of the side of the nanotube network. We first study the impact of voids on networks consisting of randomly oriented and straight nanotubes. We compute the percolation probability in these networks as a function of nanotube density for different relative void sizes ranging from 0 (no void) to 0.8. Assuming a Gaussian percolation probability density function (PDF), we find that both the mean and standard deviation of the PDF increase with increasing relative void size. We then compute the relative conductivity change as a function of nanotube density for different relative void sizes and find that it increases approximately linearly with relative void size.According to percolation theory, the conductivity of a nanotube network has a power-law dependence on nanotube density. Next, we extract the local power-law critical exponent as a function of nanotube density for different relative void sizes. We find that the critical exponent approaches 2 at high density for all relative void sizes, in agreement with previous observations for junction-resistance dominated networks without voids [1,3].Furthermore, we generate curvy carbon nanotubes using third order Bezier curves characterized by the curviness angle and aligned nanotubes using an orientation characterized by the alignment angle [1,2]. Using the same procedure as randomly oriented and straight nanotubes, we then investigate the impact of voids on the electronic properties of networks consisting of curvy and aligned nanotubes, including percolation probability, mean and standard deviation of the PDF, relative conductivity change, and nanotube density critical exponent.Our results demonstrate the impact voids have on the percolation conductivity of two-dimensional networks consisting of one-dimensional wires such as carbon nanotubes. These results also show that Monte Carlo simulations are an essential predictive tool for providing insights into the electronic properties of nanotube and nanowire networks, which are promising candidates for a wide range of applications such as flexible transparent conductors, thin film transistors, and resistive switching memory.

Achieving Remarkable Specific Mechanical Strength and Energy Absorption Capacity in SiC Nanowire Networks through Graded Structural Design.

Lightweight porous ceramics with a unique combination of superior mechanical strength and damage tolerance are in significant demand in many fields such as energy absorption, aerospace vehicles, and chemical engineering; however, it is difficult to meet these mechanical requirements with conventional porous ceramics. Here, we report a graded structure design strategy to fabricate porous ceramic nanowire networks that simultaneously possess excellent mechanical strength and energy absorption capacity. Our optimized graded nanowire networks show a compressive strength of up to 35.6 MPa at a low density of 540 mg·cm-3, giving rise to a high specific compressive strength of 65.7 kN·m·kg-1 and a high energy absorption capacity of 17.1 kJ·kg-1, owing to a homogeneous distribution of stress upon loading. These values are top performance compared to other porous ceramics, giving our materials significant potential in various engineering fields.

Fabrication of Heat-generating Polyester through Formation of Conductive Silver Nanowire Network

Fabrication of Heat-generating Polyester through Formation of Conductive Silver Nanowire Network

Stemless InSb nanowire networks and nanoflakes grown on InP

Among the experimental realization of fault-tolerant topological circuits are interconnecting nanowires with minimal disorder. Out-of-plane indium antimonide (InSb) nanowire networks formed by merging are potential candidates. Yet, their growth requires a foreign material stem usually made of InP–InAs. This stem imposes limitations, which include restricting the size of the nanowire network, inducing disorder through grain boundaries and impurity incorporation. Here, we omit the stem allowing for the growth of stemless InSb nanowire networks on an InP substrate. To enable the growth without the stem, we show that a preconditioning step using arsine (AsH3) is required before InSb growth. High-yield of stemless nanowire growth is achieved by patterning the substrate with a selective-area mask with nanohole cavities, containing restricted gold droplets from which nanowires originate. Interestingly, these nanowires are bent, posing challenges for the synthesis of interconnecting nanowire networks due to merging failure. We attribute this bending to the non-homogeneous incorporation of arsenic impurities in the InSb nanowires and the interposed lattice-mismatch. By tuning the growth parameters, we can mitigate the bending, yielding large and single crystalline InSb nanowire networks and nanoflakes. The improved size and crystal quality of these nanostructures broaden the potential of this technique for fabricating advanced quantum devices.

One-Step Synthesis of Graphene-Covered Silver Nanowires with Enhanced Stability for Heating and Strain Sensing.

Solution-processed silver nanowire (AgNW) networks have been considered as promising electrode candidates for next-generation electronic devices. However, they suffer from poor thermal and electrical stability and low mechanical properties, hindering their practical applications. In this work, graphene nanosheets are successfully introduced into AgNW via a facile one-step solvothermal process. Benefiting from increased conductive paths, the resultant AgNW/graphene films exhibit high electrical conductivity. More importantly, the interlocking NW morphology can be maintained under high temperature and applied voltage due to suppressed Ag migration, which is enabled by the introduction of graphene. This feature leads to enhanced thermal and electrical stability, making them suitable for use as transparent heaters. Furthermore, the composite films present excellent mechanical performance, and negligible resistance change is observed after 10 000 repeated bending cycles. To demonstrate their feasibility toward sensor applications, sandwiched strain sensors are designed, which can endure larger tensile strains and show higher sensitivity and repeatability compared with pure AgNW-based device. Furthermore, various hand gestures can be easily recognized by the resultant sensors based on unique combinations of sensing response. This work not only provides a low-cost method to realize large-scale synthesis of AgNW/graphene composites but also offers guidance to prepare high-performance electrodes for advanced electronics.

Exploring cyclic olefin copolymer (COC) for flexible silver nanowire electrode

The development of flexible electronic devices has been a primary focus in various fields, and silver nanowire (Ag NW) networks show significant promise due to their unique electrical and mechanical properties. However, achieving well-defined and stable nanowire coatings on polymer substrates remains challenging. This work presents a novel and simple approach for directly coating Ag NWs on cyclic olefin copolymer (COC) substrates utilizing ultraviolet/ozone (UVO) treatment, a method not previously demonstrated for this specific material system up to our knowledge. The compatibility of this approach with COC eliminates the need for complex pre- and post-treatment processes, making it a more straightforward and environmentally friendly way to improve adhesion between Ag NWs and COC. The Ag NWs/COC electrodes exhibited excellent optoelectrical performance, with a high optical transmittance of 84% and a low sheet resistance of 13 Ω/sq—metrics that compare favorably to industry standards for transparent conductive films. Additionally, the Ag NWs/COC electrodes displayed excellent mechanical stability, showing no changes in sheet resistance after both tape adhesion and film bending tests. The novelty of the presented Ag NW-COC system, combined with the simplicity and environmental benefits of the UVO coating approach, as well as the demonstrated performance and stability of the resulting electrodes, make this work a significant advancement towards realizing the commercial potential of flexible electronics for biocompatible and wearable device 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.

Metal edge confined platinum atoms in metal/hydroxide hierarchy structure for multiple hydrogen conversion and evolution

Single-atom catalysts (SACs), as a thriving subfield of catalysis, have progressed tremendously. However, the contradiction between the isolated dispersion feature of metal sites and the high mass-specific activity of the catalyst inhibits the advances of the SACs. Herein, the Pt atoms are confined at the metallic Co phase edge in two-dimensional Co/Co(OH)2 hierarchy structure (PtSA-Co@Co-Co(OH)2) by the defect inducted order electrodeposition strategy. Both integrations of in-situ/ex-situ experimental characterizations and theoretical calculation reveal that such metal edge confined Pt atoms possess an enlarged atom exposure ratio, high stability, and the like-metal electronic state contributed by metal Co 3d, which enables the Pt atoms with more suitable affinity to simultaneously bind the multiple H atoms for durable H*-H2 conversion and H2 evolution. Moreover, the metallic PtSA-Co collaborated Co/Co(OH)2 interfaces demonstrate a strong H2O dissociation capacity by the preference adsorption of H* on metallic PtSA-Co and OH*on Co/Co(OH)2 interfaces. Combining a further enhancement of constructing the catalysts on an Ag nanowire network to form a seamlessly conductive nanostructure, the PtSA-Co@Co-Co(OH)2 achieves a high mass activity with 5.92 A mg−1 at the overpotential of 100 mV in alkaline condition, 37 times to that of the benchmark Pt/C catalyst and significantly outperforming the reported catalysts. While our work has focused on the hydrogen evolution reaction, this class of metal edge collaborated single-atom catalysts may be conducive to unlock the low mass-specific activity of atomically dispersed catalysts for various processes, such as oxygen evolution reactions (OER), CO2 reduction, and biomass conversion, etc.

Cohesively improved conductivity, transparency, and stability of Ag NW flexible transparent conductive thin films by covering Al2O3 layer

Developing feasible Ag nanowire (NW) transparent conductive thin films (TCFs) with good conductivity, transparency, mechanical durability, strong adhesion, and high stability is a great challenge. Herein, novel TCFs composed of Ag NWs/Al2O3 on polyethylene terephthalate (PET) substrates with synchronously improved conductivity, transparency, mechanical durability, adhesion, and stability, are prepared. The corresponding values (before coating Al2O3: 13.0 Ω/sq. at 86.1 %, after coating Al2O3: 11.7 Ω/sq. at 87.7 %) indicate that the deposition of Al2O3 enhances the transparency and conductivity of Ag NW networks. Moreover, the resistance does not change significantly after 50 taping cycles and 2000 bending cycles with a bending radius of 5.0 mm, indicating the strong adhesion and good mechanical flexibility of Al2O3/Ag NWs composites. In addition, Al2O3/Ag NWs composites possess excellent stability to resist strong oxidizing, hot and humid environments. As a proof of concept, the flexible transparent heater prepared by Al2O3/Ag NWs composites is successfully demonstrated, verifying the practicability.

Ultra-Large Two-Dimensional Metal Nanowire Networks by Microfluidic Laminar Flow Synthesis for Formic Acid Electrooxidation.

Despite the great research interest in two-dimensional metal nanowire networks (2D MNWNs) due to their large specific surface area and abundance of unsaturated coordination atoms, their controllable synthesis still remains a significant challenge. Herein, a microfluidics laminar flow-based approach is developed, enabling the facile preparation of large-scale 2D structures with diverse alloy compositions, such as PtBi, AuBi, PdBi, PtPdBi, and PtAuCu alloys. Remarkably, these 2D MNWNs can reach sizes up to submillimeter scale (~220 μm), which is significantly larger than the evolution from the 1D or 3D counterparts that typically measure only tens of nanometers. The PdBi 2D MNWNs affords the highest specific activity for formic acid (2669.1 mA mg-1) among current unsupported catalysts, which is 103.5 times higher than Pt-black, respectively. Furthermore, in situ Fourier transform infrared (FTIR) experiments provide comprehensive evidence that PdBi 2D MNWNs catalysts can effectively prevent CO* poisoning, resulting in exceptional activity and stability for the oxidation of formic acid.

Ultra‐Large Two‐Dimensional Metal Nanowire Networks by Microfluidic Laminar Flow Synthesis for Formic Acid Electrooxidation

AbstractDespite the great research interest in two‐dimensional metal nanowire networks (2D MNWNs) due to their large specific surface area and abundance of unsaturated coordination atoms, their controllable synthesis still remains a significant challenge. Herein, a microfluidics laminar flow‐based approach is developed, enabling the facile preparation of large‐scale 2D structures with diverse alloy compositions, such as PtBi, AuBi, PdBi, PtPdBi, and PtAuCu alloys. Remarkably, these 2D MNWNs can reach sizes up to submillimeter scale (~220 μm), which is significantly larger than the evolution from the 1D or 3D counterparts that typically measure only tens of nanometers. The PdBi 2D MNWNs affords the highest specific activity for formic acid (2669.1 mA mg−1) among current unsupported catalysts, which is 103.5 times higher than Pt‐black, respectively. Furthermore, in situ Fourier transform infrared (FTIR) experiments provide comprehensive evidence that PdBi 2D MNWNs catalysts can effectively prevent CO* poisoning, resulting in exceptional activity and stability for the oxidation of formic acid.

SQUID oscillations in PbTe nanowire networks

SQUID oscillations in PbTe nanowire networks

Interconnected Pd Nanowire Networks Stereoassembled on Biomass-Derived Porous Carbon Skeletons as Bifunctional Electrocatalysts for Efficient Methanol and Formic Acid Oxidation

Interconnected Pd Nanowire Networks Stereoassembled on Biomass-Derived Porous Carbon Skeletons as Bifunctional Electrocatalysts for Efficient Methanol and Formic Acid Oxidation

Post-treatment optimization for silver nanowire networks in transparent droplet-based TENG sensors

Transparent conducting electrodes (TCEs) serve as essential components in various devices, including smart windows, thin film heaters, and sensors. Historically, indium tin oxide (ITO) thin films have served as the primary TCE material. However, the scarcity of indium in the Earth’s crust and costly vacuum-based deposition processes have prompted researchers to seek alternatives. While silver nanowire (Ag NW) networks have emerged as the leading candidate for TCEs among various alternatives, the presence of polyvinyl pyrrolidone (PVP) layer surrounding Ag NWs often leads to substantial contact resistances at the junction areas. Given the diverse characteristics of Ag NWs, including length, diameter, PVP thickness, and deposition methods, the efficacy of a specific post-treatment method on the same Ag NW batch remained unknown. This work collected effective post-treatment methods from existing literature and innovatively developed in-house approaches to optimize the treatment of Ag NW networks. Following post-treatment, the resulting electrodes exhibited a 70 % reduction in sheet resistance, with only a marginal 1 % decrease in optical transmittance. The optical figure of merit (FoM) for the optimized networks showed a remarkable five-fold improvement, rising from 66 to 305. The optimized Ag NW networks were then utilized as current collectors in water droplet-based TENG sensors, showcasing the device's effectiveness in pH and chemical concentration sensing. The fabricated TENG recorded peak Voc and Isc values of 22 V and 370 nA, respectively. Furthermore, we developed a sensor-integrated device capable of gauging the incident droplets’ pH level, signaling acid rain safety. In addition, the droplets activate a large-area Ag NW-based transparent thin film heater. Rapid defogging and defrosting capabilities of the heater was also demonstrated. The device holds the potential to be applied to the side-view mirrors of cars, providing an anti-fogging display for a significantly safer journey.

ZnO nanoarrays/Cu nanowires composite films with high haze value

In this work, we worked on compositing Cu nanowires (NWs) with ZnO nanoarrays (NAs) to enhance the light trapping abilities of transparent conductive films. A well-dispersed, crosslinked network of Cu NWs with appropriate light trapping ability was formed on the surface of the ZnO NAs, and the ZnO NAs/Cu NWs composite structures were obtained ultimately. The Cu NWs on the surface of the composite structures maintained excellent transparency and conductivity while preventing agglomeration phenomena. The ZnO NAs/Cu NWs composite films exhibited low average sheet resistance (59 Ω/sq) and high haze value (0.53) at 550 nm with uniform conductivity and exceptional light trapping performance. The composite films not only demonstrate enhanced light trapping abilities, but also exhibit improved electrical properties, making it an outstanding candidate for transparent front electrode materials in solar cell applications.

Ultrahigh Bipolar Photoresponse in a Self-Powered Ultraviolet Photodetector Based on GaN and In/Sn-Doped Ga2O3 Nanowires pn junction.

Self-powered ultraviolet photodetectors with bipolar photoresponse have great potential in the fields of ultraviolet optical communication, all-optical controlled artificial synapses, high-resolution ultraviolet imaging equipment, and multiband photoelectric detection. However, the current low optoelectronic performance limits the development of such polar switching devices. Here, we construct a self-powered ultraviolet photodetector based on GaN and In/Sn-doped Ga2O3 (IGTO) nanowires (NWs) pn junction structure. This unique nanowire/thin film structure allows GaN and IGTO to dominate the absorption of light at different wavelengths, resulting in a highly bipolar photoresponse. The device has a responsivity of 2.04 A/W and a normalized detectivity of 7.18 × 1013 Jones at 254 nm and a responsivity of -2.09 A/W and a normalized detectivity of -7 × 1013 Jones at 365 nm, both at zero bias. In addition, it has an extremely high Ilight/Idark ratio of 1.05 × 105 and ultrafast response times of 2.4/1.9 ms (at 254 nm) and 5.7/5.2 ms (at 365 nm). These excellent properties are attributed to the high specific surface area of the one-dimensional nanowire structure and the abundant voids generated by the nanowire network to enhance the absorption of light, and the p-n junction structure enables the rapid separation and transfer of photogenerated electron-hole pairs. Our findings provide a feasible strategy for high-performance wavelength-controlled polarity switching devices.

The effect of surface modification strategies on biological activity of titanium implant

The surface morphology of titanium metal is an important factor affecting its hydrophilicity and biocompatibility, and exploring the surface treatment strategy of titanium metal is an important way to improve its biocompatibility . In this study , titanium (TA4) was firstly treated by large particle sand blasting and acid etching (SLA) technology, and then the obtained SLA-TA4 was treated by single surface treatments such as alkali-heat, ultraviolet light and plasma bombardment. According to the experimental results, alkali-heat treatment is the best treatment method to improve and maintain surface hydrophilicity of titanium. Then, the nanowire network morphology of titanium surface and its biological property, formed by further surface treatments on the basis of alkali-heat treatment, were investigated. Through the cell adhesion experiment of mouse embryonic osteoblast cells (MC3T3-E1), the ability of titanium material to support cell adhesion and cell spreading was investigated after different surface treatments. The mechanism of biological activity difference of titanium surface formed by different surface treatments was investigated according to the contact angle, pit depth and roughness of the titanium sheet surface. The results showed that the SLA-TA4 titanium sheet after a treatment of alkali heat for 10 h and ultraviolet irradiation for 1 h has the best biological activity and stability. From the perspective of improving surface bioactivity of medical devices, this study has important reference value for relevant researches on surface treatment of titanium implantable medical devices.

Spiderweb-Shaped Iron-Coordinated Polymeric Network as the Novel Coating on Microneedles for Transdermal Drug Delivery Against Infectious Wounds.

Coated microneedles (CMNs) are a minimally invasive platform for immediate-release transdermal drug delivery. However, the practical applications of CMNs have been significantly hindered by the challenges associated with complex formulations, single function, and limited drug loading capacity. This study has developed a spiderweb-shaped iron-coordinated polymeric nanowire network (Fe-IDA NWs). The resulting Fe-IDA NWs are endowed with a certain viscosity due to the synergy of multiple supramolecular interactions. This allows them to replace traditional polymeric thickeners as microneedle coatings. The Fe-IDA NWs-coated microneedles (Fe-IDA MNs) display rapid disintegration in the skin model, which also enables the swift diffusion of Fe-IDA NWs and their payloads into the deeper skin layers. Additionally, Fe-IDA MNs exhibit desirable enzymatic activity and potential antibacterial ability. Thus, Fe-IDA MNs can enhance the therapeutic efficacy against wound infection through synergistic effects, and avoid the overly complicated formulation and the release of nontherapeutic molecules of conventional CMNs. As a proof-of-concept, Fe-IDA MNs loaded with chlorin e6 showed a synergistic chemodynamic-photodynamic antibacterial effect in a methicillin-resistant Staphylococcus aureus-infected wound model in mice. Collectively, this work has significant implications for the future of CMNs-based transdermal drug delivery systems and expands the application fields of metal coordination polymer (MCP) materials.