Highly Stretchable Conductors Made by Laser Draw‐Casting of Ultralong Metal Nanowires

Abstract

precisely defi ne continuous conductive lines with deterministic curvatures as shown by Rogers and co-workers, [7][8][9] leading to minimization of local strains with respect to the macroscale conductor deformation. These fl exible electrical devices can reach strains of ≈100%, but involve a series of complex fabrication steps including photolithography, e-beam or sputtering deposition, and lift-off.The performance of stretchable conductor fi lms also depends on the structural quality of the conductive elements. For example, while CNTs are theoretically as conductive as metal fi lms and wires, they have demonstrated only moderate specifi c conductivity due to short lengths and large defect density caused during synthesis, purifi cation, and functionalization. Metallic thin fi lms and nanowires made by vacuum physical vapor deposition, such as electron beam evaporation or sputtering, intrinsically offer higher electrical performance in stretchable and foldable electronics. However, their implementation is limited by the cost of vacuum processing for large area applications, and their poor mechanical properties due to the ultrafi ne-grain structure which make them brittle and prone to fracture and cracks. Solution-synthesized silver and gold nanowires [ 10,11 ] are also attractive for percolation networks. However, short (1-20 µm) nanowires [ 12 ] suffer from local contact losses and hysterisis at large strains. Recently, a hybrid multiscale design incorporating microscale diameter and centimeter-long metal wires has been used with nanoscale percolation networks to enhance the conductive performance under strain. [13][14][15][16] In this work, we report a new route to fabricate long metal micro-and nanowires by a novel laser-assisted draw-casting process, and demonstrate their integration in highly stretchable conductors reaching 700% strain while maintaining almost invariant electrical conductivity. Using this new process, Pd wires with submicron diameters and centimeter length are individually drawn at speeds close to 0.4 m s −1 . In particular, these wires represent a new route to the fabrication of high performace and reliable stretchable conductors which overcome the limitations associated with thin fi lms or percolation networks. The throughput of the wire manufacturing is scalable. While the drawing speed is limited by our current actuators, we expect that this approach can be implemented in a high throughput manufacturing setting, where bundles of wires can be drawn in parallel at speeds of several meters per second. We demonstrate a simple route to laminate the wires on fl exible substrate and measure their strain-dependent electrical conductivity. We show that as-drawn Pd wires have superior electrical conductivity and can accommodate large strains by affording higher local buckling modes without fracture.We fabricate the Pd nanowires by the LDC process to achieve a smaller diameter range than what could be reached Compliant conductors with large stretching and bending capabilities are enabling novel fl e...

Solution‐Grown Serpentine Silver Nanofiber Meshes for Stretchable Transparent Conductors

“…However, the conventional transparent conducting oxides like indium–tin oxide (ITO) and aluminum‐doped zinc oxide (AZO) are brittle and nonstretchable, which definitely hinders their application in the flexible electronics . In the past decade, a substantial amount of effort has been devoted to carbon nanotubes (CNTs) or metal nanowires (NWs) in order to fabricate stretchable transparent conductors . Among them, metal nanomeshes with the advantages of easy fabrication, high electrical conductivity, and mechanical flexibility lead the way for ITO replacement .…”

“…[6] In the past decade, a substantial amount of effort has been devoted to carbon nanotubes (CNTs) or metal nanowires (NWs) in order to fabricate stretchable transparent conductors. [7][8][9][10][11][12][13][14][15][16][17] Among them, metal nanomeshes with the advantages of easy fabrication, high electrical conductivity, and mechanical flexibility lead the way for ITO replacement. [9,11,12,[14][15][16][17] Particularly, metal nanomeshes prepared by depositing metal on various mesh templates exhibit outstanding optoelectronic performance.…”

Review of flexible and transparent thin-film transistors based on zinc oxide and related materials

“…[104] The unique advantage of Ag nanowire electrodes is their mechanical robustness, because nano-materials can be bent to much smaller radius than conventional "3D" materials. [183] Fig. 14ashows the SEM image of random meshed AgNWs on flexible substrate [182] andFig.…”

“…[104] The unique advantage of Ag nanowire electrodes is their me-chanical robustness, because nano-materials can be bent to much smaller radii than conventional "3D" materials. [183] Figure 14(a) shows the SEM image of random meshed Ag NWs on a flexible substrate [182] and figure 14(b) shows the resis-047307-10 tance change as a function of mechanical strains. [179] Compared with the small COS of ITO shown in Fig.…”