This career plan will advance the fundamental understanding of transport processes of inkjet-printed functional materials on flexible substrates through the integration of innovative research and education. The proposed research combines novel modeling and experiments that include: (i) in-situ observation and multi-scale modeling of the flow, heat and mass transfer induced by the interplay of wetting, evaporation, and self-assembly of inkjet-deposited materials; (ii) laser and plasma substrate surface modification for improved deposition in a roll-to-roll (R2R) format; and (iii) microstructural and electrical-thermalmechanical property characterization of deposited material. The focus is on the mesoscopic scale, where Marangoni flow, evaporation, and particle self-assembly can be directly observed. A lattice Boltzmann model will be developed to directly simulate drop impact and evaporation on surface modified substrates; particle-particle, particle-carrier liquid, and particle-substrate interactions; and final morphology of deposited particulate materials. In contrast to previous experiments that have only been concerned with post-mortem analysis of deposited structures, the proposed experiments will integrate ultrafast confocal microscopy and micro-particle image velocimetry systems to monitor in real-time particle self-assembly during the evaporation phase and to provide model validations. The maskless laser patterning combined with plasma etching alters substrate surface energies and hence provides wetting controls for a confined deposition. The laser-created patterns with increased surface areas due to ablative roughening will enhance adhesion of the deposited materials. Modern characterization techniques (e.g., SEM, TEM, AFM, nano-indentation, and infrared microscopy) will be used to determine final microstructures as well as electrical, thermal, and mechanical properties of deposited materials.
Intellectual Merit: Environmentally-benign R2R electronics fabrication using inkjet printing and direct laser patterning on flexible substrates is an enabling technology that will provide desired high-volume, low-cost production of flexible electronics. The proposed work will yield important understanding of how the final microstructure and properties of deposited materials depend on the electronic ink formulation, processing conditions, and substrate properties. The intrinsic limits on the spatial accuracy of ink-jetting devices, wetting, de-wetting, contact line pinning, interfacial instabilities, microflows within the deposited drop, and the self-assembly of particulate matter during drop evaporation all contribute to the lack of precise control of deposited electronic materials. The pre-patterned substrate surface will provide preferential wetting and dewetting of the inkjetted material and better substrate adhesion. This will enable more reliable deposition patterns with better edge definition, higher resolution, and improved electrical-thermal-mechanical properties of printable electronics and devices. This project will also impact other research frontiers on complex fluids involving phase change and particle assembly.
Broader Impacts: This project is an excellent fit to the strategic directions of the Center for Advanced Microelectronics Manufacturing, a national microelectronics R2R manufacturing R&D center at Binghamton. Knowledge obtained from this project will have a dramatic impact on the processing of printable electronics, ranging from low-cost consumer products, solar cells, and low-power lighting to highly specialized small scale sensors and healthcare devices. The integrated education plan seeks to enhance thermo-fluid science education through the development of new courses to highlight multiscale modeling and nanoscale phenomena at both graduate and undergraduate levels. As an offshoot of the proposed computational modeling work, courseware for virtual thermo-fluid laboratories will be developed. Through recruiting visits at local secondary schools and involvement with the local Society of Women Engineers chapter, a sustained effort to attract women and other under-represented students in engineering programs will be made. Printable electronics will be demonstrated at the Watson Engineer's Week Open House and through Summer Science Camp at the Discovery Center in Binghamton. Seminars on the processing of flexible electronics for mid-career professionals will emphasize on the structureproperty-performance relationships. The partnership with Endicott Interconnect on laser surface treatment will enable internship opportunities and foster the research to innovation transition. The collaboration with novel ink and substrate providers (e.g., Corning) will allow us to customize ink and substrate formulas for each specific application. The joint effort between the PI and Computer Science faculty at Binghamton will advance the grid computing capability via the partnership with the New York State Grid.
