Research

We have developed a practical and cost-efficient approach for the production of ultra-stretchable, highly conductive inks for 3D printing on a dispensing basis (direct ink writing). We incorporate silver (Ag) flakes into two commonly used elastomers, polydimethylsiloxane (PDMS) and thermoplastic polyurethane (TPU), which self-assemble into a conductive network through the addition of 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 a high conductivity of over 1000 S/cm with an extremely low silver content. Impressively, the stretchability of our conductors reaches 1600%, surpassing the current state of the art. The video on the left shows a data glove printed with the conductive inks using a DIW printer.

The filament consists of silver particles (Ag) as conductive fillers and a stretchable polymer matrix made of thermoplastic polyurethane (TPU). By using the capillary suspension concept, we have achieved high conductivity with only 10% Ag by volume (~51% by weight) in the resulting filament. To ensure a smooth extrusion process and to 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.

Our ongoing research focuses on the development of soft and conductive adhesives to effectively bond 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 bonds that can withstand the mechanical demands of flexible electronic systems.