Patterning Silver Nanowire Network via the Gibbs-Thomson Effect

TL;DR

The paper addresses pattern visibility in patterned AgNW transparent electrodes by introducing a Gibbs-Thomson effect–based patterning strategy. It leverages DA-modified AgNWs to seed junction-localized fragmentation and plasmonic welding at ultralow temperatures, enabling high-resolution, optically invisible patterns (down to $10~\mu m$) with minimal transmittance/haze differences ($\Delta T=1.4\%$, $\Delta H=0.3\%$). The method demonstrates practical utility by constructing a highly transparent, optoelectronic tactile e-skin and compatible stretchable sensors, highlighting low processing temperature ($T_f \approx 75^{\circ}C$) and facile three-step fabrication. This approach promises scalable, large-area manufacturing of invisible AgNW patterns for flexible, transparent electronics with improved display quality and integration capability.

Abstract

As transparent electrodes, patterned silver nanowire (AgNW) networks suffer from noticeable pattern visibility, which is an unsettled issue for practical applications such as display. Here, we introduce a Gibbs-Thomson effect (GTE)-based patterning method to effectively reduce pattern visibility. Unlike conventional top-down and bottom-up strategies that rely on selective etching, removal, or deposition of AgNWs, our approach focuses on fragmenting nanowires primarily at the junctions through the GTE. This is realized by modifying AgNWs with a compound of diphenyliodonium nitrate and silver nitrate, which aggregates into nanoparticles at the junctions of AgNWs. These nanoparticles can boost the fragmentation of nanowires at the junctions under an ultralow temperature (75°C), allow pattern transfer through a photolithographic masking operation, and enhance plasmonic welding during UV exposure. The resultant patterned electrodes have trivial differences in transmittance (ΔT = 1.4%) and haze (ΔH = 0.3%) between conductive and insulative regions, with high-resolution patterning size down to 10 μm. To demonstrate the practicality of this novel method, we constructed a highly transparent, optoelectrical interactive tactile e-skin using the patterned AgNW electrodes.

Figures (5)

• Figure 1: GTE-based patterning of AgNWs. (a-c) Schematics of the patterning procedure. (d) Photographs of the photolithography-processed (left) and GTE-induced (right) AgNW patterns. Schematics of the (e) selective deposition of DA at the junctions of AgNWs, (f) half-UV-exposed DA-AgNWs, and (g) half-fragmented AgNW network. Scanning electron microscope (SEM) image of (h) the DA-AgNWs, (i) UV-exposed DA-AgNWs, and (j) patterned DA-AgNWs. (k) Comparison of the conventional and the GTE-induced AgNW patterns in the aspect of optical visibility.
• Figure 2: (a) Schematic of the DA-based fragmentation and welding of an AgNW network. (b) Schematic of selective deposition of DA at the junction of two stacked AgNWs. (c) XRD spectra of raw AgNWs and DA-AgNWs. (d) High-resolution XPS spectra of the I 3d region for raw AgNW, DA-AgNWs, UV-treated DA-AgNWs, and heated DA-AgNWs. (e) Rs/R0of raw AgNWs and DA-AgNWs with different average diameters during annealing at different temperatures. (f) Rschange of the UV-exposed DA-AgNWs and raw AgNWs after annealing at different temperatures for 3 minutes. (g) Simulated extinction spectra of a pentagonal AgNW and experimental extinction spectrum of AgNWs. (h) Simulated electric field distribution near two stacked AgNWs at 365 nm wavelength, the white arrows indicate the vectorial electric field. (i) Absorption spectrum of DA, spectrum of the UV source, and the HG spectrum obtained by an FDTD simulation. (j) Rschange of raw AgNW, D-AgNW, and DA-AgNWs networks before and after UV and UV & heating treatment. (k) SEM image of the welded AgNWs.
• Figure 3: High-resolution patterns of DA-AgNWs. (a-j) OM images of the patterned DA-AgNW networks with different graphic designs. The side length of the squares in (g) is 50 $\mu$m. (h) The pattern with a fixed linewidth of 50 $\mu$m and spacings gradually reduced from 100 to 10 $\mu$m. The linewidths of (i-j) are 50 $\mu$m and 30 $\mu$m, respectively. (k)-(l) SEM images of the AgNW patterns with linewidths of 20 $\mu$m and 10 $\mu$m, respectively.
• Figure 4: Pattern Invisibility. (a) Differences in light passing through a substrate for a conventional AgNW pattern and the GTE-induced AgNW pattern. (b) Simulated absorption, scattering, and extinction efficiency of AgNWs with different diameters. (c) Simulated electric field intensity distribution of the conventional and GTE-induced AgNW patterns. (d) Profiles of the electric field intensity at 10 nm below the AgNWs extracted from (c). (e) Transmittance and (f) haze difference between the conductive and insulative regions of the DA-AgNW patterns with different RS. (g) Photograph of the patterned DA-AgNW electrode.
• Figure 5: Tactile system based on the DA-AgNW patterns. (a) Schematic of the optoelectronic interactive tactile system. Photographs of (b) the tactile sensor on the skin, (c) the system, and (d) working demonstration of touch-responsive LED lighting. (e) Relative capacitance variation of the sensor array in response to single-pixel touch and sliding gestures along a row or column of pixels. (f) Capacitance map of $\Delta$CXY /CX0Y0 induced by touching the position (2,2) showing the local capacitance variation during a single-point touch.