Stretchable Conductors through the Deposition of Carbonaceous Particle Suspensions on Fabrics of Elastomer Fibers

Abstract

The necessity for stretchable conductors has increased over the past decade due to numerous emerging applications such as stretchable electronics and biosensors for use in the human body. In particular, stretchable conductors that lend themselves to scalable fabrication methods such as printing are desirable due to their commercial potential. Past work regarding the production of printable, stretchable conductors has focused on the deposition of conductive polymers such as PEDOT:PSS on stretchable substrates. While these composites exhibit conductivity of 10⁻1 {10⁰ S/m, the polymer coating limits stretchability, resulting in either mechanical failure or large conductivity loss at 60-80% strain. Here, I explore the usage of carbonaceous materials as an alternative conductive coating, in order to match or potentially exceed conductivity achieved in past work while maintaining the elastic properties of the stretchable substrate. Through experiments with three carbonaceous fillers (single-particle carbon black (SP-CB), fractal carbon black (F-CB) and Functionalized Graphene Sheets (FGS)), I attempt to understand the material properties that distinguish good conductive fillers for printable, stretchable conductors. Two different methods were used to deposit SP-CB, F-CB and FGS on a commercial Spandex-Nylon blend. Most depositions in this thesis were done utilizing a filter-casting method in which a carbon black or FGS suspension was poured on the samples and pulled through by vacuum. SP-CB coating provided the best results, generating conductivity of 10⁰ S/m stable up to ~250% strain (far more strain than endured by past printable, stretchable conductors.) When applied as a thick film, FGS coating resulted in conductivity on the order of 101 S/m, but conductivity decreased exponentially after 40% strain. Contiguousness of the graphene and fractal carbon black coatings were shown to be inhibited by the size of particle aggregates formed in suspension, thus limiting conductivity of these coatings.