Sprayed Graphene-Based Coating Enabling Antifog and Smart Features

Large-area and low-cost coatings introducing electrical, optical, thermal, and surface control functionalities are highly demanded in the fields of flexible and wearable electronics for applications ranging from agrifood and smart packaging to electronic textiles and aerospace. Here, we report a graphene-based coating with combined antifog, electrical, and thermal functionalities suitable for spray deposition on commercially recyclable plastic substrates. A graphene ink formulation in a low-boiling-point solvent, stabilized by polyvinylpyrrolidone, enables compatibility with deposition processes in the coating industry. Spray-coated graphene films on polyethylene demonstrated antifog properties, achieving a 1.5-fold reduction in the contact angle at a 5% higher optical transmittance compared to commercial antifog coatings. Mechanical testing revealed more than a 1.8-fold improvement in Young's modulus compared to the bare polyethylene. Moreover, by depositing another thin film of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) underneath the graphene coating, electrical conductivity (sheet resistance of about 330 Ω/sq) with similar transparency can be achieved. Testing of the thermal properties of the film demonstrated how these conductive coatings can be used as heaters, reaching about 50 °C at a 30 V bias. Moreover, the graphene smart antifog coating showed a 97% improvement in thermal conductivity, increasing to 283% for the graphene/PEDOT:PSS multilayer coating with respect to the PE. The integration of these combined and novel smart functionalities on commercial recyclable plastic widens the application arena of smart coatings beyond agrifood, toward packaging, automotive, and aerospace fields.