Sustainable Biopolymer Binders for Conformable Multifunctional Electrically Conductive Coatings

There is a growing demand for transitioning electronic circuitry and components from stiff and rigid substrates to compliant and flexible platforms, such as thin plastics, textiles, and foams. In parallel, the push for replacing expensive metals-based inks with cost-effective conductive inks has led to the development of formulations with novel nanomaterials and binders.[1,2] Among the nanomaterials, 2D materials, and in particular graphene-related materials (GRMs), have drawn attention due to their increasingly facile and scalable production, high electrical conductivity, and compatibility with industrial manufacturing methods.[3] The resulting conformable electronic materials are poised to unlock thrilling applications in the wearable, healthcare, and Internet of Things sectors. Nevertheless, the substrates, the binders, and the solvents employed are so far often selected without considering the outcome in terms of material sustainability.<br/><br/>We developed electrically conductive composite coatings based on GRMs and biobased and/or biodegradable binders.[2,4] The fabrication is simple and exploits green solvents such as alcohol and/or water. Sustainable binders, ranging from biopolymers and natural waxes such as polyvinyl alcohol and beeswax to proteins from the waste stream such as keratin extracted from wool/feather wastes, were preferred depending on the selected sustainable substrates (i.e., cellulose-/biopolymer-based). The as-obtained materials display a low sheet resistance of about 10 Ohm/sq and excellent stability to tens of folding events, hundreds of abrasions, and thousands of bending cycles. Thus, they can be applied as deformable conductors or strain sensors, depending on the material formulation (i.e., 2D-1D nanofiller hybridization and binder:nanofiller ratio) and the consequent electrical percolation preservation/disruption after mechanical stress. These materials are multifunctional since they exhibit enhanced thermal conductivities. As such, they can be applied simultaneously for thermal dissipation and electromagnetic interference shielding. Due to their flexibility, multifunctionality, and reduced footprint, such versatile electrically conductive coatings have the potential to enable applications in the wearables and conformable electronics field, reducing the environmental impact of the conductive materials for electronics simultaneously.<br/> <br/>References:<br/>[1] Ergoktas M. S. et al., <b>2020</b>, Nano Letters, DOI:10.1021/acs.nanolett.0c01694.<br/>[2] Cataldi P. et al., <b>2020</b>, Advanced Functional Materials, DOI:10.1002/adfm.201907301.<br/>[3] a) Kovtun A., <b>2019</b>, 2D Materials, DOI:10.1088/2053-1583/aafc6e; b) Cataldi et al., <b>2018</b>, Applied Sciences, DOI:10.3390/app8091438.<br/>[4] a) Wu et al., <b>2020</b>, Advanced Electronics Materials, DOI: 10.1002/aelm.202000232; b) Cataldi et al., <b>2019</b>, ACS Sustainable Chemistry and Engineering, DOI: acssuschemeng.9b02415.