Omnidirectionally Stretchable Metal Films with Preformed Radial Nanocracks for Soft Electronics

Abstract

Flexible and stretchable conductive thin films are required for the development of soft electronics; however, few existing films satisfy the requirements for both electrical/ mechanical performances and process practicability. This study describes a simple approach to fabricate omnidirectionally and highly stretchable nanocracked metal thin films on thiolated elastomeric substrates by exploiting the eruption of a residual solvent contained in an elastomeric substrate during metal thermal evaporation. Also, the effects of residual solvent content in the substrate on the crack topography of a metal thin film and its resultant stretching characteristics are investigated. The solvent content in the range of 0.2−0.3 wt % facilitates the formation of radial nanocracks with a high density of small cracks, which is most suitable for dissipating omnidirectional tensile stress. When a strain of 100% is applied to the elastomeric substrate, the electrical resistance of the radially nanocracked stretchable Au film increases only slightly compared to that of the uncracked Au film. Furthermore, the film shows high stability under repeated stretching cycles and harsh mechanical conditions, enabling its application to stretchable interconnects for a flexible light-emitting diode array. This method provides an effective approach to obtain high-quality thin metal electrodes for use in flexible and wearable devices.

Advances in Biodegradable Electronic Skin: Material Progress and Recent Applications in Sensing, Robotics, and Human–Machine Interfaces

“…It mimics some of the biological skin senses and provides a promising sensing platform for key application areas such as wearable sensors, robotics, and prosthetics (Figure 1). [1,[4][5][6][7][8][9][10][11] However, serious concerns have arisen regarding the production of electronic waste (e-waste), the influence of e-skin on human health, the safety of wearable electronic devices, costs, and environmental limitations. These concerns have encouraged researchers to develop biocompatible, renewable, sustainable, and biodegradable flexible wearable detection devices and biosensing platforms.…”

Surface Wrinkling for Flexible and Stretchable Sensors

“…The formation of surface wrinkles in the conductive layers of the substrates enhances the contact interface, surface area, and current pathways, which significantly improve the sensing response and performance. [3,4,95] The ultrasensitive flexible sensors and transparent electrodes, comprising a conducting material and a soft substrate, are essential components for the fabrication of e-skins, photoelectronics, POC diagnostics platforms, and implantable electronics. In this section, we will discuss the application of engineered wrinkle formations in the development of various types of sensors, such as strain, pressure, temperature, photonic, and chemical sensors.…”

Pushing the Limits of Flexibility and Stretchability of Solar Cells: A Review

“…have demonstrated that the dependence of thin film surface geometry obtained from gold evaporation on elastomeric thiolated support. [ 181 ] They showed that radially nanocracked films present a higher stretchability than uncracked films, because the propagation of cracks is retarded in the stretching direction.…”