Permittivity tensor imaging: modular label-free imaging of 3D dry mass and 3D orientation at high resolution
Li-Hao Yeh, Ivan E. Ivanov, Talon Chandler, Janie R. Byrum, Bryant B. Chhun, Syuan-Ming Guo, C. B. Foltz, Ezzat Hashemi, Juan A. Pérez-Bermejo, Huijun Wang, Yan‐Hao Yu, Peter G. Kazansky, Bruce R. Conklin, May Han, Shalin B. Mehta
Abstract
The dry mass and the orientation of biomolecules can be imaged without a label by measuring their permittivity tensor (PT), which describes how biomolecules affect the phase and polarization of light. Three-dimensional (3D) imaging of PT has been challenging. We present a label-free computational microscopy technique, PT imaging (PTI), for the 3D measurement of PT. PTI encodes the invisible PT into images using oblique illumination, polarization-sensitive detection and volumetric sampling. PT is decoded from the data with a vectorial imaging model and a multi-channel inverse algorithm, assuming uniaxial symmetry in each voxel. We demonstrate high-resolution imaging of PT of isotropic beads, anisotropic glass targets, mouse brain tissue, infected cells and histology slides. PTI outperforms previous label-free imaging techniques such as vector tomography, ptychography and light-field imaging in resolving the 3D orientation and symmetry of organelles, cells and tissue. We provide open-source software and modular hardware to enable the adoption of the method.