Fabrication of Highly Transparent and Flexible NanoMesh Electrode via Self‐assembly of Ultrathin Gold Nanowires

Abstract

new design principles. Nanomaterials, such as carbon nanotubes, [1,3,4,[12][13][14] graphene, [15,16] and metal nanowires [8,9,[17][18][19][20][21][22][23][24] have been recently explored and demonstrated their potentials to flexible TE overcoming shortcoming of current ITObased TE (brittleness, low inferred transmittance, and earth rareness). Despite this potential, it remains challenging to achieve high conductivity and high transparency without deterioration under repeated bending and stretching cycles. In this context, metal mesh/grid is emerging as a promising solution, which achieved exceptionally low-sheet resistance and high optical transparency. [25][26][27] The fabrication of mesh-like electrodes could be achieved by top-down [25][26][27][28] and bottomup [29,30] approaches. Self-assembled meshlike structure have been successfully demonstrated by using silver and gold nanoparticles. [29,30] However, to the best of our knowledge, self-assembled mesh geometry based on 1D nanowire materials has not been reported. Here, we report a simple yet efficient solution-based, equipment-free interfacial self-assembly strategy to fabricate mesh TE (mTE) using ultrathin gold nanowires. Unlike other metal nanomaterials, ultrathin gold nanowires we used possess a serpentine morphology due to its ultrathin width (≈2 nm) and ultrahigh aspect ratio (>10 000). [31][32][33] Briefly, freshly synthesized AuNWs hexane solutions were purified and aged prior to spreading onto air-water interface. During the hexane evaporation, AuNWs could self-assemble into bundles with a mesh-like network. The partial removal of oleyamine ligands during aging may be the reason for the bundle formation. [34] The bundles had a typical thickness of 193.7 ± 67.6 nm and mesh pore sizes varied from 8 μm to 52 μm, depending on 100 random pores at aging time of 12 h. The resulting mesh film is easily transferred to a variety of substrate, exhibiting a sheet resistance of ≈40 times smaller than our previous nonmeshed film [18] under the similar optical transmittance of ≈92%. Moreover, our mesh electrode is patternable and washable with excellent flexibility, which could be directly used for touch screen and flexible circuit of light emitting devices (LEDs). We believe our approach opens a new route to flexible TE for applications in future soft electronic sensors, displays and energy-harvesting devices.Transparent electrodes simultaneously require high electrical conductivity and high optical transparency, which have been achieved with mesh metal structures. However, most currently fabricated micro-and nanoelectronic devices are produced via top-down lithography methods. Here, a bottomup self-assembly approach to fabricate mesh electrode using ultrathin gold nanowires (AuNWs) at the air/water interface is reported. Slow partial ligand removal during the aging process is the key for the formation of such self-assembled mesh structures. The resulting mesh film has a typical mesh pore size of 8-52 μm, with a sheet resistance of ≈40 times smaller than our pr...

Toward Soft Skin‐Like Wearable and Implantable Energy Devices

“…[47] Similar properties have been observed by high quality copper nanowires, which are earth-abundant and much cheaper than AgNWs. [48] In addition, ultrathin gold nanowires (AuNW) with a diameter of only 2 nm and a high aspect ratio of >10000 exhibited inherent curved morphologies, emerging as intrinsically stretchable building blocks for stretchable electronics, including wearable sensors, [4e,49] transparent electrodes, [50] and stretchable supercapacitors. [51] In particular, the self-assembled transparent (T = 90% at a wavelength of 550 nm) AuNWs film (≈8 nm) could allow a stretchability of 50% with reversible resistance changes of only 45%, due to a strain induced wrinkle structure (Figure 6d,e).…”

Polyurethane foam coated with a multi-walled carbon nanotube/polyaniline nanocomposite for a skin-like stretchable array of multi-functional sensors

“…The MFSF on TRT can be cut automatically using a cutting machine (Silhouette, Lindon, UT, USA). 23,24 The excess MFSF segment was detached from the TRT using tweezers. Then it was peeled from the cutting mat.…”

A Moss‐Inspired Electroless Gold‐Coating Strategy Toward Stretchable Fiber Conductors by Dry Spinning

“…[8][9][10][11][12][13][14][15][16][17] However, the mixing method requires high volume ratio of conductive filler in the elastic substrate, which usually reduces elasticity; [10,12] whereas, the coating method often raises concerns of delamination due to Young's modulus mismatch between elastomeric polymers and active materials. [7,[20][21][22][23] The AuNWs could be well mixed with elastic styrene-ethylenebutylene-styrene (SEBS) block copolymer in tetrahydrofuran (THF) to form a viscous and volatile spinning solution to form AuNWs/SEBS fibers in the air. The former approach can lead to highly elastic polymer fiber rapidly, but it requires high temperature to melt the raw materials, hence, limits to the scope of available suitable materials.…”

“…The former approach can lead to highly elastic polymer fiber rapidly, but it requires high temperature to melt the raw materials, hence, limits to the scope of available suitable materials. [7] In many of those applications, stretchable Nevertheless, it requires an excessive solution to solidify fibers (e.g., wet spinning), highvoltage conditions (e.g., electrospinning).…”

“…[7,[20][21][22][23] The AuNWs could be well mixed with elastic styrene-ethylenebutylene-styrene (SEBS) block copolymer in tetrahydrofuran (THF) to form a viscous and volatile spinning solution to form AuNWs/SEBS fibers in the air. Ultrathin AuNWs were soft, flexible, and analogous to polymeric chains due to small diameter (2 nm), high aspect ratio (>10 000) and good dispersibility, which has been used in various soft sensing and energy devices.…”