Conductive Nanowire Networks Research Articles

Bioinspired Impact-Resistant and Self-Monitoring Nanofibrous Composites.

Lightweight and impact-resistant materials with self-monitoring capability are highly desired for protective applications, but are challenging to be artificially fabricated. Herein, a scalable-manufactured aramid nanofiber (ANF)-based composite combining these key properties is presented. Inspired by the strengthening and toughening mechanisms relying on recoverable interfaces commonly existing in biological composites, mechanically weak but dense hydrogen bonds are introduced into the ANF interfaces to achieve simultaneously enhanced tensile strength (300MPa), toughness (55MJ m-3 ), and impact resistance of the nanofibrous composite. The achieved mechanical property combination displays attractive advantages compared with that of most of previously reported nanocomposites. Additionally, the nanofibrous composite is designed with a capability for real-time self-monitoring of its structural safety during both quasi-static tensile and dynamic impact processes, based on the strain/damage-induced resistance variations of a conductive nanowire network inside it. These comprehensive properties enable the present nanofibrous composite with promising potential for protective applications.

Thermoresponsive Transient Radio Frequency Antennas: Toward Triggered Wireless Transient Circuits

AbstractWhile implantable medical devices offer tremendous potential for treating a myriad of diseases and disorders, there are many situations in which such devices are only needed for short time periods, with extended presence or surgical removal leading to a host of undesired complications. To address this concern, researchers are working to develop implantable circuitry that eventually disintegrates. Prior work in this area leveraged known bioresorbable materials, but the lifetime of circuits formed from such materials is determined upon fabrication, and on‐demand, triggered disintegration is not possible. To better match the lifetime of an implanted device to the status of the condition it is monitoring or treating, it would be advantageous to be able to noninvasively trigger disintegration at a particular time, avoiding situations in which the device lifetime is either too short or too long. Thus, to enable implantable circuitry with wireless capabilities that can disintegrate upon external stimuli, thermoresponsive transient RF antennas are formed that exhibit stable wireless response in warm aqueous environments but disintegrate and irreversibly lose functionality when cooled below a critical temperature. Antennas are formed by embedding patterned networks of silver nanowires in a thermoresponsive polymeric binder, which maintains network conductivity in warm solution but disintegrates and releases the nanowires when solution temperature drops. Mild sintering enhances electrical properties of the conductive nanowire network and antenna response while maintaining the capability for disintegration. To reduce the undesired effects of swelling, devices are sandwiched between two parylene films. These thermoresponsive transient devices represent an important step toward the realization of wireless medical implants whose disintegration can be triggered at any time by an external cooling stimulus.

Effect of nanowire curviness on the percolation resistivity of transparent, conductive metal nanowire networks

We study the effect of nanowire curviness on the percolation resistivity of transparent, conductive metal nanowire networks by Monte Carlo simulations. We generate curvy nanowires as one-dimensional sticks using 3rd-order Bézier curves. The degree of curviness in the network is quantified by the concept of curviness angle and curl ratio. We systematically study the interaction between the effect of curviness and five other nanowire/device parameters on the network resistivity, namely nanowire density, nanowire length, device length, device width, and nanowire alignment. We find that the resistivity exhibits a power law dependence on the curl ratio, which is a signature of percolation transport. In each case, we extract the power-law scaling critical exponents and explain the results using geometrical and physical arguments. The value of the curl ratio critical exponent is not universal, but increases as the other nanowire/device parameters drive the network toward the percolation threshold. We find that, for randomly oriented networks, curviness is undesirable since it increases the resistivity. For well-aligned networks, on the other hand, some curviness is highly desirable, since the resistivity minimum occurs for partially curvy nanowires. We explain these results by considering the two competing effects of curviness on the percolation resistivity. The results presented in this work can be extended to any network, film, or nanocomposite consisting of one-dimensional nanoelements. Our results show that Monte Carlo simulations are an essential predictive tool for both studying the percolation transport and optimizing the electronic properties of transparent, conductive nanowire networks for a wide range of applications.

Interdependence of Resistance and Optical Transmission in Conductive Nanowire Networks

AbstractMetallic nanowire networks show great potential for use in transparent conductive displays. The coupled relationship between the principal materials properties of interest for such applications, optical transmittance and sheet resistance, is known to be affected by both nanowire dimensions and area coverage. Existing theory to describe the observed interdependence requires consideration of both bulk and surface phases. Here, an analysis of structural variables in these materials is presented confirming that bulk considerations do not typically apply. Accordingly, a model using statistical theory for random line networks is developed that requires consideration of a surface phase only. The resultant simple expression relates sheet resistance and optical transmission of heterogeneous nanowire assemblies in terms of nanowire dimensions. Comparison of our model with experimental and simulation data from the literature shows excellent agreement. In closing, theoretical insights into the observed influence on sheet resistance of polydisperse nanowire lengths and structural variability are provided.

Facile fabrication of transparent and conductive nanowire networks by wet chemical etching with an electrospun nanofiber mask template

Two-dimensional aluminum (Al) nanowire (NW) networks offering transparent conductors were fabricated by simple wet etching of Al metalized polymer film using a polystyrene (PS) nanofiber (NF) mask template. NW networks—500nm in width, 50nm in thickness, and with an area fraction of 22.0%—was prepared by electrospinning PS with 283nm in diameter on a metalized film, bonding the NF to the film by annealing at 200°C, etching unmasked Al and then dissolving the PS mask. The NW width and the area fraction of Al NW network can be controlled readily by the NF diameter and the deposition time of PS NF mask, respectively. The NW networks thus prepared are flexible and exhibit 80% optical transmittance and sheet resistance of 45Ωsq−1, indicating that they can be an indium-tin oxide (ITO) replacement.

Transparent Nanowire Network Electrode for Textured Semiconductors

This work presents an inexpensive and easily manufacturable, highly conductive and transparent nanowire network electrode for textured semiconductors. It is based on lines of silver nanoparticles transformed into a nanowire network by microwave or furnace sintering. The nanonetwork electrode on crystalline silicon is demonstrated experimentally, with the nanoparticles self-assembling in the valleys between the pyramids of the textured surface. Optical experiments show that this conductive nanowire network electrode can be essentially 'invisible' when covered with the conventional anti-reflection coating (ARC), and thus could be employed in photovoltaic applications.

Three‐Dimensional Conductive Nanowire Networks for Maximizing Anode Performance in Microbial Fuel Cells

Pore genius: A nanoporous composite of graphite felt and polyaniline was developed and used as the anode of a microbial fuel cell, resulting in an order of magnitude increase in power output. The hierarchical conductive anode is a promising strategy for constructing highly efficient microbial fuel cells (see figure).