A colloidal membrane is one rod-length thick fluid monolayer that spontaneously assembles in the presence of a non-adsorbing polymer. Including the transformation from a flat 2D colloidal membrane to an edgeless 3D colloidal vesicle, colloidal membranes undergo a range of remarkable morphological and topological shape changes, yet quantitative insight into such dynamics is limited due to the limitations of the existing imaging techniques. Here, we present a study on the dynamics of colloidal membranes by employing dielectric tensor tomography (DTT). By recording diffracted light from colloidal membranes for various illumination angles, the principles of DTT enables the reconstruction of the 3D tomograms of directors and principal refractive indices with high temporal resolution without fluorescence labeling or mechanical scanning for 3D imaging. Using the technique, we investigated the forming and closing dynamics of transient pores on colloidal vesicles in response to changing osmotic pressure, and the orientational change of constituent rod particles around the pore.
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