Biodegradable, ionic thermoelectric composites via self-assembly of dipeptides and deep eutectic solvents

Abstract

The growing demand for biodegradable conductive composites is driven by the need to mitigate electronic waste and advance bioelectronics for healthcare applications. Self-assembled peptide composites, particularly diphenylalanine (FF) derivatives, represent a promising class of materials for such electronics due to their inherent biodegradability and ease of hybridization with functional materials. However, the integration of ionic species with these peptides is often limited by the disruption of non-covalent interactions between FF derivatives. In this study, we developed biodegradable, ionic thermoelectric composites by co-assembling Fmoc-FF with deep eutectic solvents (DESs) composed of choline chloride (ChCl) and ethylene glycol (EG). Spectroscopic analyses revealed that Fmoc-FF formed eutectogels through π-π interactions between Fmoc groups, resulting in a highly porous colloidal network. The Fmoc-FF eutectogels exhibited an ionic conductivity of up to 47.5 mS？·cm？1 and a Seebeck coefficient of 7.39 mV？·K？1, making them suitable for heat harvesting. Additionally, they were entirely degraded within 48 h under proteolytic conditions, confirming their biodegradability. The eutectogels also displayed self-healing and shear-thinning behaviors, highlighting compatibility with additive manufacturing techniques for device integration.