Direct Embedment and Alignment of Silver Nanowires by Inkjet Printing for Stretchable Conductors

Abstract

Stretchable conductors have attracted tremendous attention owing to their potential applications as electrodes and sensing elements for wearable electronic devices. In this study, we have developed an inkjet printing process to directly embed and align silver nanowires in the polydimethylsiloxane elastomer for stretchable conductors. Instead of printing on top of elastomers, we printed the silver nanowires directly into an uncured liquid elastomer layer to embed the conductive nanowires, therefore eliminating the problems with surface wetting and delamination in conventional approaches, where the conductor is patterned on top of elastomers. This study investigated the process controls to tune the embedment depth and alignment of silver nanowires through inkjet printing. The printing process was captured with a high-speed camera to elucidate the mechanisms that direct the printed features. By controlling the thickness of the liquid elastomer layer and the post-printing treatment of printed lines, stretchable conductors composed of embedded silver nanowires have been fabricated in a single step. Because of the reflow of the viscous liquid elastomer, the printed silver nanowires are aligned along the printing direction, resulting in linewidth of tens of micrometers upon solvent removal. The stretchable conductors showed good mechanical and electrical stability under repeated bending and stretching/releasing cycles. This method of directly embedding silver nanowires into a liquid elastomer offers facile heterogeneous integration for digital patterning of stretchable electronics.

Highly Conductive Silicone Elastomers via Environment‐Friendly Swelling and In Situ Synthesis of Silver Nanoparticles

“…Similar phenomena have been reported. [ 53,54 ] The 10.8% drop in resistance can be attributed to the conditioning process of the AgNPs on the wrinkled elastomer films, where they tend to rearrange themselves to achieve stable point‐to‐point contacts due to the cyclic stretching/releasing. [ 55 ] It is interesting to note that this behavior at the first stretching cycle has not been observed when gradually increasing the strains (Figure 3f), probably due to the conditioning and rearranging of the conductive path during stretching at the smaller strains.…”

Recent Advances in High-Throughput Nanomaterial Manufacturing for Hybrid Flexible Bioelectronics

“…Unlike NPs, NWs are differentiated by their large aspect ratios, with lengths often 1000 times greater than their widths [ 3 , 11 , 111 ]. As a result of these aspect ratios, NWs can from conductive networks with very minimal loading, exhibit minimal bending stiffness and exceptional yield strength approaching the theoretical value of E (Young’s modulus)/10, high optical transmittance, and electrical conductivities that are dominated by quantum effects [ 17 , 45 , 112 ]. When the NW widths become too small, conductivity is greatly diminished by edge effects from atoms at the material surface and scattering, setting a practical limit on widths for printed inks [ 112 ].…”

“…Compared to NPs, NW inks are significantly easier to synthesize because NWs in random orientations are much more resistant to agglomeration [ 11 ]. Unlike sintered NP sheets, these NW networks can stretch and deform when embedded in a polymer matrix [ 45 ]. NWs can also be made biocompatible because of the inability of small Ag particles to migrate into the skin [ 111 ].…”

Enhanced Piezoelectric Properties of Poly(Vinylidenefluoride-Co-Trifluoroethylene)/Carbon-Based Nanomaterial Composite Films for Pressure Sensing Applications

“…Recent years have witnessed a consistent rise in public demand for electronic products [1], among which wearable devices have gained attention for their comfort, flexibility, and durability [2,3].…”

“…Recent years have witnessed a consistent rise in public demand for electronic products [ 1 ], among which wearable devices have gained attention for their comfort, flexibility, and durability [ 2 , 3 ]. Meanwhile, in order to reduce global energy consumption, the development of alternative energy continues to gain traction [ 4 ].…”