Highly stretchable patternable conductive circuits and wearable strain sensors based on polydimethylsiloxane and silver nanoparticles

Abstract

Patterned circuits on highly stretchable conductive films are critical in the practical application of next-generation flexible and wearable devices. Currently, most patterned circuits do not exhibit highly stretchable properties, and a lithography process in vacuum is required. In this study, silver nanoparticles (AgNPs) and liquid polydimethylsiloxane (PDMS) are mixed together to form liquid conductive adhesives (CAs). Various stretchable patterned circuits are prepared using this CA to achieve all required functions. Six basic patterns, including rhombus, straight lines, serpentine, triangle, ellipses, and fold line, are studied for their stretchable and electrical properties. The film is found to maintain excellent conductivity after withstanding tensile strain of up to 320% and more than 10 000 stretching-releasing cycles of 0%–150%. More than 86% of visible lights can be penetrated through the film due to the transparent substrates. Functional and wearable devices are manufactured, and devices fabricated from rhombus-pattern circuits are found to exhibit stable electrical conductivity when subjected to very high tensile strains. According to the sensitivity of the straight-line patterned circuit to strain, a repeatable use sensitive strain sensor is studied. Also, two types of artificial electrical skin are demonstrated.