Self-healing of Direct Written Conductive Inks for Curvilinear Circuits
Date
2023-04-18
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Abstract
The increased electrification of vehicles in both automotive and aerospace industries has introduced new challenges in manufacturing complexities and weight management. Complex and heavy wirings are currently being utilized and conventional printed circuit board (PCB) manufacturing methods are limited in 2D geometries. Alternatively, a direct-writing approach presents weight and materials saving opportunities where planar substrates with circuits already printed are formed to a final shape. However, designing a circuit or a printed ink formula able to withstand the high strain of substrate forming is challenging. Instead, a circuit able to regain functionality after sustaining strain induced cracks presents a more versatile approach. In this study, a conductive ink with self-healing capabilities is developed. A copper-nanoparticle based ink compatible with existing lithographic methods is developed and printed on planar polymeric substrates. Intense pulsed light (IPL) is utilized to photothermally heat, reduce, and sinter copper nanoparticles within milliseconds. By utilizing light-matter energy absorption and the plasmonic effect, heat sensitive polymeric substrates are unaffected while conductive copper tracks are formed. After printing, drying, and IPL flashing, the substrate and printed tracks are subjected to cyclic bending and thermoforming. Afterwards flashing is performed once again to initiate the healing process through reflow of indium microparticles. These indium healing agents added to the ink bridges microcracks via capillary forces to recover severed electron pathways. Mechanisms of photothermal heating and sintering is simulated to better understand the underlying physical phenomena. Ultimately, a planarly written copper nanoparticle ink capable of surviving substrate deformation to produce curvilinear circuits is achieved. This direct writing method can provide drastic wiring weight reduction imparting fuel savings in the next generation of electronics in vehicles.
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Keywords
direct written circuits, copper nanoparticle, self-healing, intense pulsed light, sintering
Citation
Jeong, R. (2023). Self-healing of direct written conductive inks for curvilinear circuits (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.