Koen Visscher is an Associate Professor in the Department of Physics with an interest in Biological Physics. He holds joint appointments in Molecular and Cellular Biology as well as in the College of Optical Sciences, and is a member of the Applied Mathematics Graduate Interdisciplinary Program. His research focuses on the role of mechanical force in Biology using single-molecule techniques such as optical tweezers. He pioneered the so called molecular force clamp, a feedback controlled optical tweezers that is able to maintain a constant force on a single individual moving motor protein. Recent interests are RNA structure, nucleic acid-protein interactions interactions, and translational recoding via -1 frameshifting.