Ag nanowire-based transparent stretchable tactile sensor recognizing strain directions and pressure

Abstract

In the last decade, extensive studies have been conducted to realize the functions of human skin based on stretchable electronics. An artificial skin, recognizing complex mechanical stimulation including pressure, strain and shear, and composed of transparent material, is an essential goal but has hardly been achieved. We fabricated a transparent integrated sensor system that can sense the strain direction and normal pressure of applied mechanical stimulation. Each sensor is composed of micropatterned Ag nanowire, forming a composite stretchable conductor with a block copolymer elastomer. The micropatterning and transfer process using thermoplastic elastomer facilitates the transparent conductor to show high transmittance with low sheet resistance at the same time. The designed transparent strain sensor responds linearly to strain, but does not respond to the orthogonal direction, which enables it to have strain-directionality. The applied mechanical signal, comprising normal force and directional strain, can be interpreted through the electrical signal observed from integrated sensors.

Recent Progress in Transparent Conductors Based on Nanomaterials: Advancements and Challenges

“…Silver nanowires (AgNWs), with their excellent conductivity and high anticorrosion properties, are the most intently studied among MeNWs. They remain at the forefront of TSC research as they have demonstrated their versatility in various fabrication techniques 41,43,48,62–66. Araki et al used laser induced forward transfer (LIFT), a noncontact printing technique, to make a prestrained electrode that stretched to 100% with a change of only 1.6 times the initial resistance 62.…”

“…Since particles in the spray are very small and evaporation during spraying occurs almost simultaneously, results of the coating are not commonly affected by fluidic effects such as Marangoni flow. In fabrication of TSCs, this method typically is used to coat 1D nanomaterials like CNT69 and MeNWs 64,66,69,73…”

“…There are various techniques for filtrating and transferring nanomaterials, but vacuum filtration and transfer are major methods 34,43,46,47,53,57,64,65,72. The nanomaterial solution is filtrated through a filter membrane and resulting film is transferred to a target substrate using vacuum pressure ( Figure d).…”

“…Besides vacuum filtration and transfer and wet transfer, several methods to fabricate transparent and stretchable electrodes are reported. Transfer methods entail coating stretchable polymer onto the nanomaterials' coated sacrificial layer and peeling off the polymer layer 54,64,80. Since nanomaterials are naturally embedded in substrates, electrodes can be mechanically stable.…”

“…Patterning micromesh or nanomesh can be an effective approach to enhancing the stretchability and transparency of conductors. This patterning can be carried out by imprinting,64 laser patterning,63 and lithography 64. Wang et al enhanced stretchability and transparency of AgNW networks by the laser‐patterning process 63.…”