CAREER: Roll-to-Roll Fabrication of Porous Materials Using Nanobubble Templates

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This Faculty Early Career Development (CAREER) grant explores a new manufacturing approach for creating templated, nanoporous materials that is compatible with high-throughput, scalable manufacturing protocols, including roll-to-roll fabrication. Nanoporous materials are materials characterized by pore sizes in the sub-micrometer range (for reference a human hair is approximately 20 micrometers). They have many important applications in electrochemical energy storage, catalysis, ion separation and tissue engineering. In electrochemical cells, including batteries and supercapacitors, electrode pore structure is critical to achieving good transport of ions and electrons through the cell, thus enabling higher energy and power densities. While numerous methods exist for synthesizing electrodes with controlled pore structures, there is a critical need to find new approaches for fabricating templated, nanoporous materials that are compatible with the high-throughput, roll-to-roll manufacturing processes currently employed in industries such as battery production. This project explores a new porous material manufacturing approach that uses nanoscale bubble templates in place of traditional hard templating materials, thus enabling precise control over the resulting porous structure while eliminating process complexities and waste associated with removal of the hard-templating material. The research is integrated with an educational plan that supports the training of graduate and undergraduate student researchers, enhances educational opportunities in the field of nanomanufacturing, and creates new opportunities for underrepresented minority groups in STEM, with a focus on Native Hawaiian and Pacific Islander students.The specific goal of this research is to test the hypothesis that nanosized bubbles can be used as templates to fabricate meso- and macroporous materials, and that the pore structures of these materials can be precisely engineered by controlling the size distribution and position of the bubbles during the templating process. The research addresses the follow key question: Can nanoscale bubbles be used to controllably template porous structures across micro-to-millimeter thick films at manufacturing rates compatible with meter-per-second scale (i.e. roll-to-roll) processing? The research addresses gaps in current knowledge of nanobubbles, including: i) mechanisms of solid film formation at nanobubble three-phase (gas-liquid-solid) interfaces; ii) the physics of nanobubble generation and stability, and iii) the precision with which nanobubble positions can be manipulated using methods such as acoustic standing waves. The research also tests new methods for real-time investigations of nanobubbles using in-situ liquid scanning transmission electron microscopy to advance fundamental knowledge of nanobubble interfaces and stability. Overall, the research and education plans establish the PI’s long-term career in advanced manufacturing of nanoscale materials for electrochemical energy storage and other applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.