Research

Optical diffraction tomography (ODT) is an optical analogue of x-ray CT imaging. ODT can quantitatively measure the 3D refractive index distribution of specimens, which is linearly proportional to the mass density of most biomolecules such as proteins and nucleic acids.

We are working on the development and improvement of the optics setup to provide the refractive index tomogram with better spatial and temporal resolution, and the application of ODT to various biological samples to investigate the mass density changes in cells and tissues under different pathophysiological conditions.

Brillouin microscopy offers the ability to measure mechanical properties of biological samples in a non-contact and label-free manner.

By applying Brillouin microscopy, we characterize tiny frequency shifts of light caused by the interaction between collective vibration of molecules (acoustic phonon) and photon, which are related with longitudinal modulus, refractive index, and density of materials. From the measured longitudinal modulus of cells and tissues in various conditions, we are studying the underlying mechanism and biological relevance how cells and tissues

Light can transfer momentum to matter through light-matter interaction in forms of absorption, transmission, reflection, or refraction of light at the dielectric interfaces. Tightly-focused laser beam can exert gradient force on particles and trap them.

By accessing 3D mass density distribution with ODT and manipulating the wavefront of the trapping beam accordingly with holographic optical tweezers, we can control the position and orientation of samples having arbitrary shape and heterogeneous density distribution, which has been rather challenging.