Direct Laser Patterning of Copper-Graphene Composite Structures for Flexible Electronics

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This proposed research program will focus on direct laser writing process for rapid fabrication of copper-graphene (Cu-Gr) composite structures on various substrates for electronic applications by deeply understanding the correlations between laser processing conditions and interfacial structure of copper nanograins and/or copper-to-graphene junctions as well as electrical / thermal properties of composite structures and ultimately the performance of prototype flexible electronics. Three objectives of this research are to: (i) develop a one-step direct writing process for rapid patterning of Cu-Gr composite on various substrates; (ii) investigate the laser-induced heat generation, Cu nanoparticle formation and joining, polymer fast pyrolysis and Gr structure growing processes, particularly linking the laser heat generation to microstructures and defects at the interface of Cu-to-Cu and Cu-to-Gr to their conductivities; and (iii) design and fabricate prototype flexible electronics by utilizing different electrical and thermal properties of as-written Cu and / or Cu-Gr composite structures, and study their functions and performance related to microstructures and environmental stimuli. This research will use copper ion (e.g., Cu2+ and Cu+) and water soluble polymer (e.g., polyvinyl pyrrolidone-PVP, polyethylene glycol-PEG, and tannin) ink to coat the surface of substrates (plastics, silicon, paper) after proper surface treatment. Laser writing parameters will include laser power, scanning speed, wavelength, etc. Advanced analytical techniques will be used to investigate the formation of Cu and Gr and the defects at the interfaces of Cu grains or Cu-to-Gr. Electrical / thermal conductivities and mechanical property of as-written structures will be characterized. Simulations will be used to understand the growth of Gr on Cu surface under laser irradiation in a short time period. The as-written pure Cu and Cu-Gr composite structures will be integrated into functional devices on flexible substrates such as gas / strain sensor and photodetector to test their performances. The successful execution of this research program will provide a fundamental understanding of scientific phenomena in laser-mater interactions and microstructure-property correlation in materials science, specifically in laser heat generation, melting and solidification of metallic copper, atomic diffusion during joining, carbonization and crystallization of laser converted graphene, and effects of interfacial structures or defects on properties. This is of vital importance in practical applications, such as electronic fabrication and performance. This research program will also train 3 PhD and 3 MASc students and 3 PDFs with cutting edge knowledge and professional skills. These students and trainees will then contribute their knowledge and skills in industries, academic and research institutions to enhance Canada's future competitiveness in innovation and creativity.