Super-Resolution Two-Dimensional Infrared Imaging

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With support from the Chemical Measurement and Imaging (CMI) Program in the Division of Chemistry, Dr. Arnaldo Serrano and his group at the University of Notre Dame are developing a technique to image the dynamics of molecules on a time scale that matches the fastest chemical reactions, shorter than a picosecond (one trillionth of a second), and on a length scale that allows them to resolve events inside of a single cell. Imaging methods that can provide chemical information with both high time resolution and high spatial resolution can help answer detailed questions about the chemistry of highly nonuniform microscopic environments, such as the interior of a cell. To make such measurements possible, the research team is investigating several approaches to overcome the so-called “diffraction-limit” for infrared light, which is the smallest possible length scale that can be imaged using traditional techniques. One approach the team is pursuing involves recording images with microscopic spheres that act as tiny magnifying glasses. Another approach involves patterning the incoming light to take advantage of “aliasing”, the same effect the causes moiré patterns when looking through two picket fences, in order to extract more detailed information from a measurement in order to reconstruct high-resolution images. These efforts hold promise for eventually enabling new measurements of the chemical heterogeneity inside living cells. The project also includes a plan to organize a “Midwest Ultrafast Spectroscopy and Imaging Graduate Workshop”, where graduate students in the region can learn about advanced optical methods and network with colleagues.This project will investigate methods for enhancing the spatial resolution of wide-field two-dimensional infrared (2DIR) microscopy. Recent developments in infrared imaging, including wide-field 2DIR microscopy, make it possible to measure the ultrafast dynamics of materials on the micron-scale. While 2DIR microscopy enables a new kind of label-free imaging, the technique is still in its infancy and remains limited by the low spatial resolution (about 3 microns) of infrared optics. This project takes advantage of the intrinsic nonlinearity of 2DIR signals to make ultrafast vibrational measurements in the nanometer regime using microsphere-enabled near-field enhancements and structured illumination microscopy (SIM). Such enhancements of the resolution would enable ultrafast IR imaging on a wide variety of heterogenous systems, such as infrared plasmonic devices and the subcellular structures of biological samples. The broader impacts of the work include advanced training opportunities for graduate and undergraduate research students, and educational outreach activities emphasizing mathematics skills in physical science courses at the high school and undergraduate levels.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.