Nanofillers to Improve the Barrier Properties of Biobased Substrates of Flexible Printed Electronics

Abstract

Printed electronics offer many benefits compared to conventional electronics. For example, printed supercapacitors are promising for energy storage, but the traditional substrates are nonsustainable. Replacing them with biopolymers enables a more ecofriendly solution for more sustainable devices. However, in supercapacitors with liquid electrolytes the substrate also has to have good barrier properties to prevent electrolyte evaporation, which biopolymers typically do not have without improvement. In this study, impermeable nanofillers are mixed into polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-hydroxyvalerate (PHBV) in an effort to improve their barrier properties enough to be usable in supercapacitors with longer lifetimes without allowing for significant electrolyte evaporation. Out of a selection of nanoclays and a nanocellulose, the nanoclay Nanomer I.28E is chosen as the best filler, as it leads to the best barrier properties and flexibility when mixed with PHB. 20 w-% of Nanomer I.28E is chosen as the best amount of filler as it reduces the permeability the most, although it unfortunately also makes the material less flexible. The prepared substrate is found to be sufficient for a supercapacitor with a lifetime of 1 year, allowing for the use of more sustainable materials in printed supercapacitors.