(440d) Towards Constructing the Potential Landscape of a Colloidal Ellipsoid with Scattering Morphology Resolved Total Internal Reflection Microscopy (SMR-TIRM)

Nano/microscale colloidal particles exist in various applications, such as paints, milk, and blood. Their properties are influentially affected by the relevant surface interactions between the particles and the boundaries. To measure such colloidal interactions, Total Internal Refraction Microscopy (TIRM) is one of the techniques that could be employed, and herein, we will present our recent progress on developing a TIRM variant, called Scattering Morphology Resolved Total Internal Reflection (SMR-TIRM), which was conducted to anisotropic colloidal particles. SMR-TIRM experiments were performed on our customized rotatable apparatus with a series of no-backlight 8-bit images taken for every 10° of azimuthal angles (φ) on different particles. For an ellipsoid with a specific orientation, like the conventional TIRM, SMR-TIRM uses the total integrated light scattering intensity (I) to track the separation distance (h) between the particle and boundary in the Brownian fluctuation. It further utilizes the morphology of light scattering to resolve the orientation of ellipsoid by using 2D Gaussian analysis to quantitatively measure the angles (M_φ) and aspect ratios (M_AR) of the morphologies. We found an empirical equation to demonstrate the relationship between the M_φ and the φ of the ellipsoid, and M_AR was used to assess the polar angle (θ) of the ellipsoid. The summarized result suggests the scattering morphology dependence on the orientation of an ellipsoid, which was then combined with our previous simulation results to tentatively construct the potential energy profile.