A High Aspect Ratio Serpentine Structure for Use As a Strain‐Insensitive, Stretchable Transparent Conductor

Abstract

The development of strain-insensitive stretchable transparent conductors (TCs) is essential for manufacturing stretchable electronics. Despite recent progress, achieving a high optoelectronic performance under applied strain of 50% continues to present a significant challenge in this research field. Herein, an ultratall and ultrathin high aspect ratio serpentine metal structure is described that exhibits a remarkable stretching ability (the resistance remains constant under applied strain of 100%) and simultaneously provides an excellent transparent conducting performance (with a sheet resistance of 7.6 Ω  and a transmittance of 90.5%). It is demonstrated that the highly stretchable transparent conducting properties can be attributed to the high aspect ratio feature. A high aspect ratio (aspect ratio of 17-367) structure permits facile deformation of the serpentine structure with in-plane motion, leading to a high stretching ability. In addition, this structural feature avoids the classic tradeoff between optical transmittance and electrical conductance, providing a high electrical conductance without decreasing the optical transmittance. The practical utility of these devices is tested by using these TCs as stretchable interconnectors among LEDs or in wearable VOC gas sensors.

Materials and Structures toward Soft Electronics

“…The serpentine patterns are typically fabricated by lithography‐based microfabrication, cut‐and‐paste manufacturing, and laser ablation . Metals are the most commonly used for the serpentine interconnections due to their excellent conductivity and low cost . Other materials such as graphene, silicon, ZnO, and ITO can also be patterned into serpentine layouts for special purposes such as transparency and energy harvesting …”

3D Printed Reduced Graphene Oxide/Elastomer Resin Composite with Structural Modulated Sensitivity for Flexible Strain Sensor

“…This rhombic structure with aspect ratio can transform the whole tensile strain into local bending strain or otherwise transfer or reduce strain energy during tensile process. [54,55] Figure S4, Supporting Information, shows rhombic structure with different θ angles (tan θ ¼ 0.5, 1, 1.5) and dimensions for the 3D printed composite electrode. Figure 5a shows the tensile process of an electrode with rhombic structure at tan θ ¼ 0.5.…”

Recent Progress in Simple and Cost‐Effective Top‐Down Lithography for ≈10 nm Scale Nanopatterns: From Edge Lithography to Secondary Sputtering Lithography

“…In 2017, a serpentine structure was used as a prepattern for improved stretching performance, and a photoresistbased microscale serpentine structure was fabricated, and a wall structure was made by SSL ( Figure 9e). [170] The resulting pattern had a very high aspect ratio (up to ≈300 because of collapse at over 300), and also a transparent electrode was fabricated though embedment in PDMS. The new transparent electrode showed much better stretch force than that previously developed, and the transmittance was also sustained high.…”