High-conductivity graphene/carbon black inks via interpenetrating networks for wearable fabric-based heaters and strain sensors

Abstract

Graphene composite conductive inks are promising for the scalable production of printable electronics, and multifunctional coatings, owing to their cost-effectiveness, high conductivity, and remarkable flexibility. However, the restacking of graphene (Gr) sheets and agglomeration of carbon black (CB) significantly reduce the conductivity of aqueous graphene composite inks, limiting the exploration of high-performance devices. Herein, a highly conductive and dispersed graphene composite ink, based on a composite system of two- and zero-dimensional carbon materials was developed by a scalable sand-milling method. Carboxymethyl cellulose (CMC) can effectively address the aggregation issues of Gr and CB through steric hindrance. Functionalized Gr and CB can synergistically form an interpenetrating conductive network structure. The synthesis of a highly dispersed Gr/CB composite was facilitated by an in situ exfoliation process, which resulted in a high electrical conductivity of 2.12 × 10⁴ S m⁻¹ (i.e., a sheet resistance of 2.16 Ω sq⁻¹). A screen-printed Gr/CB @ thermoplastic polyurethane fabric based on the Gr/CB composite ink exhibited an excellent electrical conductivity (7.08 Ω sq⁻¹). The resulting composite fabric demonstrated promising potential for application in low-voltage driven wearable heaters and ultra-sensitive flexible strain sensors, while being waterproof, stable, and comfortable, suggesting significant potential for use in flexible wearable electronics.