1175784 - Imaging Moving Aerosol Particles Using Nano Digital Holographic Microscopy (Nano-DIHM): Beyond the Diffraction Barrier (Student Poster #16)

In-situ and real-time characterization of the size, phase, and morphology of aerosol particles is vital to several fundamental and applied research domains, including atmospheric chemistry and physics, air quality, climate change, and human health. To date, it has not been possible to use digital holographic microscopy to image moving airborne nanosized particles without optical traps. In this study, we constructed a novel integrated digital in-line holographic microscopy system coupled with a flow tube (Nano-DIHM), in which moving aerosol particles were imaged. We demonstrated this technique’s ability to successfully characterize: 1) particle phase, shape, morphology, 2) 4D dynamic trajectories (position in space at frequent time points), and 3) 3D dimensions of airborne particles ranging from the nanoscale to the microscale. In summary, we demonstrated for the first time the successful application of Nano-DIHM for nanosized particles (≤ 200 nm) in dynamic systems without optical traps. The Nano-DIHM allows observation of moving particles in 3D space and simultaneous measurement of each particle's three dimensions. As a proof of concept, we report the real-time observation of 100 nm and 200 nm particles in the air and aqueous/solid/heterogeneous phases. The analyzed particles were polystyrene latex spheres and the mixture of metal oxide nanoparticles. The particles were successfully imaged in both the stationary (immobilized) and dynamic (free-flowing aerosol) modes. The novel Nano-DIHM technique was validated by high-resolution scanning/transmission electron microscopy (S/TEM) and aerosol sizers. The broad applicability of this new experimental technique is expected to open new directions in applied and fundamental particle research. Next-generation numerical algorithms and more advanced hardware will likely advance the performance of Nano-DIHM for remote and automated observation of complex matrices, opening the door to applications of Nano-DIHM in domains ranging from industrial process monitoring to observations of planetary atmospheres.