MRI: Development of a time-resolved, high resolution nonlinear optical microscope for interfacial studies

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This award is supported by the Major Research Instrumentation (MRI), the Chemistry Research Instrumentation (CRIF) and the Chemical Measurement and Imaging (CMI) Programs. Professor Eric Borguet from Temple University and colleague Hai-Lung Dai have developed a time-resolved, high resolution optical microscope. This microscope employs a laser to probe samples such as protein membranes in living cells or nanomaterials such as the surfaces of gold nanoparticles. The interaction of the laser with the sample produces an image of the material under study. Being able to image interfaces with time resolution and molecular specificity is important to the understanding of a wide variety of biological, chemical and materials systems. For example, it is an important approach for examining interfacial water molecules. This new microscope affords the capability to record images illustrating water structure at the interface between a biological cell and a substrate which is information critical for understanding cell adhesion. It is used to monitor molecular adsorption (for example drugs) and transport at membranes of living cells. Graduate students are involved in the development and testing of the instrument, receiving training in an important skill sought by commercial instrument firms. Once the instrument is available for use, undergraduates will receive training in its usage in laboratory courses. Multiple investigators from various universities are utilizing this resource.This research is aimed at enhancing research and education at all levels. The microscope records images of samples at millisecond time intervals and with submicron spatial resolution producing second order nonlinear optical signals. This microscope uses an optical fiber based laser system which provides high repetition rate, high pulse energy, ultrafast laser pulses in a broad wavelength range in the visible, and IR to facilitate resonantly enhanced second harmonic generation (SHG) and sum frequency generation (SFG) from a variety of materials and molecules at surfaces/interfaces. The microscope enables imaging of molecular transport with region-specificity at living cell membranes. In addition, it permits examination of non-specific cell adhesion using nonlinear vibrational microscopy and the observation of molecular interactions at the surfaces of colloidal objects. The instrumentation is also used for the study of two-dimensional materials at interfaces using nonlinear optical microscopy and for determining inner and outer nuclear membrane protein orientation and distribution in live cells. The microscope also serves researchers probing surface-bound ligands on gold nanoparticles and visualizing electronic symmetry breaking in quantum materials. It is also being used for the evaluation of cartilage tissue engineering strategies by IR imaging, and for imaging of leukocyte-endothelial interaction in a novel organ-on-a-chip system using time-resolved, high-resolution imaging.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.