Most living cells do not absorb or scatter light significantly, i.e. they are essentially transparent, or phase objects. Phase contrast microscopy proposed by Zernike in the 1930’s represents a major advance in intrinsic contrast imaging, as it reveals inner details of transparent structures without staining or tagging. While phase contrast is sensitive to minute optical path-length changes in the cell, down to the nanoscale, the information retrieved is only qualitative. Quantifying cell-induced shifts in the optical path-lengths permits nanometer scale measurements of structures and motions in a non-contact, non-invasive manner. Thus, quantitative phase imaging (QPI) has recently become an active field of study and various experimental approaches have been proposed.
Recently, we have developed Spatial Light Interference microscopy (SLIM) as a highly sensitive QPI method. Due to its sub-nanometer pathlength sensitivity, SLIM enables interesting structure and dynamics studies over broad spatial (nanometers-centimeters) and temporal (milliseconds-weeks) scales. I will review our recent results on applying SLIM to basic cell studies, such as intracellular transport and cell growth. I will end with a discussion on using SLIM for label-free diagnosis of blood and biopsies.
Gabriel Popescu received the B.S. and M.S. in Physics from University of Bucharest, in 1995 and 1996, respectively. He obtained his M.S. in Optics in 1999 and the Ph.D. in Optics in 2002 from the School of Optics/ CREOL (now the College of Optics and Photonics), University of Central Florida. Dr. Popescu continued his training with the G. R. Harrison Spectroscopy Laboratory at M.I.T., working as a postdoctoral associate. He joined University of Illinois at Urbana-Champaign in August 2007 as an Assistant Professor in the Department of Electrical and Computer Engineering and holds a full faculty appointment with the Beckman Institute for Advance Science and Technology. He is also an affiliate faculty in the Bioengineering Department. Prof. Popescu received the 2009 NSF CAREER Award, was the 2012 Innovation Discovery Finalist selected by the Office of Technology Management Office, UIUC, and was elected as the 2012-2013 Fellow of the Center for Advanced Studies at UIUC. Dr. Popescu is an Associate Editor of Optics Express and Biomedical Optics Express, and Editorial Board Member for Journal of Biomedical Optics.