Ice Lithography – A Novel Nanomanufacturing Process

This project catalyzes an innovative ice lithography nanomanufacturing research and education hub, which currently does not exist in the United States. Lithography is a cornerstone technology of the modern era, enabling a range of common electronic devices including cellular phones, computers, and energy harvesting devices. Conventional lithography based on liquid phase resist processing is well suited for patterning flat solid-state surfaces such as silicon wafers. This grant supports research to advance high precision lithography beyond robust planar substrates. Ice lithography is a dry nanomanufacturing process that is amenable to functionalizing delicate and complex surfaces such as free-standing three-dimensional nanostructures or biological macromolecules. Additionally, the small molecular dimensions of the condensed gasses employed as sacrificial resist layers in ice lithography yield very high resolution. The project involves interdisciplinary fundamental research in nanomanufacturing and nanopatterning leading to novel device applications which benefits the US economy, health, and prosperity. It brings together a team of researchers with expertise in condensed matter physics, biophysics, astrochemistry, chemistry, and mechanical engineering. A broad range of students including women and underrepresented minorities are trained by the project. The project involves community outreach to high school students from central Missouri, who design and fabricate their own “nanoscale ice sculptures” while learning the basics of high precision lithography and device design. Using traditional polymer resists on freestanding or nonplanar structures for electron-beam lithography is not just impractical, it is often impossible due to liquid surface tension or solvent effects. Additionally, conventional resists have limitations with their ultimate resolution, leave behind residues, and are not ecologically friendly. A manufacturing process which could robustly and precisely arrange metal or semiconducting features on complicated substrate surfaces such as peptide nanostructures or vanishingly sharp atomic force microscope tips, would lead to a paradigm shift in nanofabrication. Ice lithography, which employs solid-phase condensed gasses (amorphous ices) as sacrificial resists offers a generalizable path for patterning delicate, free-standing, or three-dimensional structures including biological macromolecules that deform or denature if exposed to conventional liquid-phase resists. This project employs a customized cryogenic scanning electron microscope to etch ice resists by e-beam lithography, metallize the resist and lift it off to fabricate novel nanostructures on biological and other soft material surfaces thus creating new devices and systems. Through this research, a high-precision manufacturing process is developed for multiple applications, including nanodevices for immunosensing. 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.