Enhanced stretchable electronics made by fused-filament fabrication

Abstract

3D printing is widely used for manufacturing complex non-functional parts, and recently, the fabrication of electronics has also attracted research attention. The commercialized process of fused-filament fabrication (FFF), which is still evolving,has been used in the preparation of basic electronic conductors and sensors but only a few studies of more complex structures with integrated circuits and passive components have been reported. Notably, the usage of FFF in wearable stretchable electronics has not been studied previously. We demonstrate that the combination of FFF printing and commonly used stretchable electronics materials and methods enables new wearable stretchable electronics. In this study, thermoplastics were extruded directly onto a stretchable substrate and their adhesion was measured using T-peel tests. The test results were further used in the fabrication of supports for meander-shaped screen-printed interconnects. The elongation of the interconnects with the supports were studied by tensile tests with simultaneous measurements of the electrical conductivity. The results were good, and the adhesion exceeded the constitution of the substrate when the filament and the substrate were of the same material type. The average bond strength was ∼2 N mm-1. Support structures placed close to the meander-shaped interconnects changed the interconnects' deformation under elongation. The average maximum elongation of the interconnects was improved by ∼27% when the supports directed stresses away from the interconnects' weak areas. Conversely, the results were ∼21% lower when the supports directed stresses towards the weak areas. This study demonstrates that it is possible to use direct 3D printing onto highly stretchable substrates. Currently, commercial FFF materials and methods can be used to manufacture supports, frames and other non-functional parts on wearable electronics substrates in a single process step. We believe that in the future, FFF will become a valuable tool in the manufacture of inexpensive and reliable wearable electronics.