Nilanthi Warnasooriya, a postdoctoral research associate in the Department of Biomedical Engineering at Texas A&M University, will give a talk Monday (Feb. 1) at 4:10 p.m. in Room 104 of the Jack E. Brown Engineering Building on campus.

Warnasooriya’s talk, “Three-wavelength Phase Imaging Interference Microscopy and Heterodyne Holographic Microscopy for 3D Imaging of Live Cells Labeled with Gold Nanoparticles,” is part of the biomedical engineering department’s seminar series.


This talk consists of two main parts. The first part describes a three-wavelength phase imaging interference microscopy technique and the second half of the talk describes a heterodyne holographic technique for imaging live cells tagged with gold nanoparticles. Three-wavelength phase imaging interference microscopy combines phaseshifting interferometry with three-wavelength optical phase unwrapping. This technique consists of a standard Michelson-type interferometer. The reference mirror is dithered for obtaining interference images at four phase quadratures, which are then combined to calculate the phase of the object surface. The 2? ambiguities are removed by repeating the experiment at three different wavelengths, which yields phase images of effective wavelength much longer than the original, without increasing phase noise. The resulting image is a profile of the object surface with a height resolution of several nanometers and range of several microns.

Heterodyne holographic microscopy in total internal reflection is used for 3D imaging of live 3T3 mouse fibroblasts labeled with 40nm gold particles. The method can be effectively used to distinguish nanoparticles from the cellular environment due to the difference in scattering efficiencies of particles and cells, and has the potential to be

used in biological applications.

Submitted by Nicole Priolo,