CAREER: High-Aspect-Ratio Multi-Material Three-Dimensional Microstructures via Microfluidic Direct Laser Writing

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This Faculty Early Career Development (CAREER) grant will focus on understanding and advancing a novel additive manufacturing strategy to enable entirely new paradigms of multi-material, and in turn multi-functional, three-dimensional (3D) structures at sub-micron scales for emerging scientific applications. The ability to manufacture geometrically complex yet functionally advantageous microsystems comprised of multiple fully-integrated materials—corresponding to desired optical, biological, chemical, electrical, and/or mechanical properties—offers the potential to revolutionize a multitude of fields, including biomedicine, optics and photonics, metamaterials, and microrobotics. A recently created additive manufacturing technique, "microfluidic direct laser writing," is uniquely suited to realize such capabilities. By using tightly-focused laser pulses to solidify distinct, sequentially loaded photoreactive liquids in designated locations, this approach allows for multi-material 3D microstructures to be built with unparalleled geometric versatility at 100-nanometer length scales. Current methods of additive manufacturing at this scale appear to be limited to building 3D constructs with small height-to-width aspect ratios. This research project seeks to understand, explain, and ultimately control the fundamental process mechanisms that have heretofore hindered the use of direct laser writing for printing multi-material 3D microstructures with large aspect ratios. In concert, this CAREER program will establish education and outreach activities that are either directly integrated with or inspired by the research plans, including: (i) non-competitive additive manufacturing activities for high school women, (ii) year-long integrated research projects for high school students, (iii) a four-year-long Honors Thesis project for undergraduate students, and (iv) new multi-material projects for the additive manufacturing curriculum. By leveraging the unique accessibility of additive manufacturing (or colloquially, "3D printing"), these activities are expected to increase science and engineering exposure and inspire a lasting interest and confidence in advanced manufacturing research for high school, undergraduate, and graduate students, with an emphasis on inclusion for women and students of color.The overarching goal of the research is to uncover and access regions of the microfluidic direct laser writing processing design space to achieve accurate and repeatable manufacturing of entirely new classes of multi-material 3D nanostructured components that are not restricted to low aspect ratios. At present, the roles of underlying microfluidic direct laser writing process factors—namely, those stemming from two-photon polymerization phenomena and microscale mechano-fluidic interactions—remain poorly understood. To bridge these knowledge gaps, this research project will combine theoretical and experimental studies to systematically investigate and reveal the fundamental relationships connecting: (i) the point-by-point, layer-by-layer writing path of the scanning laser, (ii) microfluidic infusion conditions, (iii) mechanical and shrinkage-based microstructure deformation dynamics, and (iv) material misalignment error propagation during intermediate microfluidic direct laser writing stages. It is envisioned that the results of the research activities will catalyze new technologies for optical, biomedical, and microelectronics applications in academic, commercial, and governmental sectors. This project will allow the PI to significantly advance the state of knowledge in multi-material additive micro/nanomanufacturing, expand the use of direct laser writing, and firmly establish the PI's long-term career in advanced manufacturing.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.