Highly Stretchable and Durable Conductive Knitted Fabrics for the Skins of Soft Robots

Stretchability and durability are imperative features for many electronic skins of soft robots, particularly those involving high deformability, cyclic gaits, confined space traverse, rough terrain navigation, and frequent human-robot interaction. This article reports on the design, fabrication, and characterization of highly stretchable and durable interconnections based on conductive knitted fabrics for the skins of soft robots. The core-spun yarn containing an ultrafine metal wire (core diameter: 50 μm) fabricated using a newly developed vortex spinning technology is employed as the conductive trace and is integrated into rib-knitted fabrics together with two types of elastic composite yarns-an elastic filament yarn and an elastic vortex core-spun yarn, respectively. Owing to the structures and properties of the yarns and fabrics, the electrical resistance of the fabrics remains stable at a maximum strain of 425% in unidirectional tensile test and a maximum average membrane strain of 300% in three-dimensional deformation. The fabrics exhibit a fatigue life greater than 1,200,000 loading cycles at 20% tensile strain and 10,000 abrasion cycles. Application of the fabrics is demonstrated by covering an origami paper-fabric composite-based soft extension actuator with the fabric. Performance of the developed conductive knitted fabrics indicates that they have potential to find application in the electronic skins of soft robots.