Sustainable thermal interface materials from recycled cotton textiles and graphene nanoplatelets

Fabrication of thermal interface materials (TIMs) from sustainable resources is a very challenging task but at the same time of great importance due to the continuously growing problem of electronic waste management. A variety of TIMs comprising synthetic polymers loaded with metallic wires or ceramic nanofillers are commercially available; however, they are usually frail and difficult to recycle. In this letter, we report a simple fabrication process for sustainable bio-based TIMs using regenerated cellulose and graphene nanoplatelets (GnPs). The process relies on forming conductive inks by dissolving post-consumer cotton fabrics and dispersing GnPs in a common solvent, followed by solution casting/drying. The TIM pads become electrically conductive (30 S/m) at 25 wt. % GnP concentrations. Their cross-plane thermal conductivity (k) was estimated to be 5.50 W/mK using infrared thermal measurements on a chip-stack setup. Additionally, the surface or in-plane 2D thermal conductivity was found to be approximately 800 W/mK. In the case of damage, the TIMs can be recycled by re-dispersing in the solvent.