Single-shot Volumetric Chemical Imaging by Mid-Infrared Photothermal Fourier Light Field Microscopy

Three-dimensional molecular imaging of living organisms and cells plays a significant role in modern biology. Yet, current volumetric imaging modalities are largely fluorescence-based and thus lack chemical content information. Mid-infrared photothermal microscopy as a new chemical imaging technology provides infrared spectroscopic information at sub-micrometer spatial resolution. Here, by harnessing thermosensitive fluorescent dyes to sense the mid-infrared photothermal effect, we demonstrate mid-infrared photothermal Fourier light field (MIP-FLF) microscopy for single-shot volumetric infrared spectroscopic imaging at the speed of 8 volumes per second and sub-micron spatial resolution. Protein contents in bacteria and lipid droplets in living pancreatic cancer cells are visualized. Altered lipid metabolism in drug-resistant pancreatic cancer cells is observed with the MIP-FLF microscope. ### Competing Interest Statement J.X.C. declares a financial interest with Photothermal Spectroscopy Corp.