Formulating Stretchable Conductive Inks for Direct Ink Writing (DIW) Type 3D Printers.


We have developed a practical and cost-effective approach to produce ultra-stretchable, highly conductive inks for dispensing-based 3D printing (Direct Ink Writing). To do this, we incorporate silver (Ag) flakes into two commonly used elastomers, polydimethylsiloxane (PDMS) and thermoplastic polyurethane (TPU), which self-assemble into a conductive network by adding a secondary liquid called capillary suspension. This innovative capillary force-induced self-assembly technique not only reduced silver consumption by more than 50% compared to commercial ink formulations, but also achieved high conductivity of more than 1000 S/cm with an extremely low silver content. Impressively, the stretchability of our conductors reached 1600%, surpassing the current state of the art. Video on the left shows a data glove printed with the conductive inks via a DIW printer. 

Extrusion of stretchable conductive filament for Fused Filament Fabrication (FFF) type 3D printers.

The filament consists of silver particles (Ag) as conductive fillers and a stretchable polymer matrix of thermoplastic polyurethane (TPU). By using the capillary suspension concept, we achieved high conductivity with only 10 vol% Ag (~51 wt%) in the resulting filament. To ensure a smooth extrusion process and prevent phase separation and damage to the conductive particle network, we used an extrusion agent in the production of the granules. The lower consumption of solid particles and the addition of the extrusion agent enabled a smooth extrusion process without clogging the nozzles.

Soft and conductive adhesives for joining soft substrates and rigid electrical components in hybrid flexible electronics.

Our ongoing research focuses on the development of soft and conductive adhesives to effectively join soft substrates and rigid electrical components in hybrid flexible electronics. By exploring innovative formulations and integrating advanced bonding techniques, we aim to create reliable and robust interconnects that can withstand the mechanical demands of flexible electronic systems.