Towards sustainable transparent flexible heaters: Integration of a BNNT interlayer using green solvent substitution

Processing materials in electronics with non-toxic, green solvents can provide environmental benefits while reducing manufacturing health and safety challenges. Unfortunately, green solvents are often unable to provide comparable solubilizing characteristics and present challenges in printing and film formation compared to conventional organic solvents. Therefore, green materials are often developed in parallel to their processing method for successful implementation. In this study, we report on the use of a polyvinyl butyral (PVB) and ethanol solution as a replacement for poly (3-hexylthiophene-2,5-diyl) (P3HT) and chloroform and its’ first demonstration in boron nitride nanotube (BNNT) thin film interlayers for improved thermal and mechanical performance in silver microgrid transparent heaters. Using PVB/ethanol led to comparable thin films of BNNT, achieving a clear tube network formation across the substrate surface and resulting in near identical optical transparency and surface energy measurements compared to the P3HT/chloroform system. Silver microgrids printed on BNNT-coated polyethylene terephthalate (PET) with PVB as dispersant exhibited a similar conductive performance to the microgrids printed on BNNT-coated PET with P3HT, providing the same level of mechanical endurance and maintaining thermal performance metrics upon applied voltage. The PVB and ethanol system presents an exemplary green material combination for the novel deposition of BNNT thin film interlayers for integration into transparent heaters.