Twists and Turns in Orbital Angular Momentum and Cell Mechanics Jennifer E. Curtis Department of Biophysical Chemistry U. of Heidelberg This talk focuses on two aspects of light-matter interaction and their technological applications using holographic optical tweezers (HOT). An optical tweezer, or optical trap, is a tightly focused beam of light that can attract and hold dielectric objects in its focus. There is an entire tool box of such optical manipulation techniques, whose rapid expansion has been fueled by the development of HOT. With relative ease, HOT produces one to hundreds of conventional and non-conventional optical traps, that may be positioned and moved at will in three dimensions. One of the most exciting of these manipulation tools is the optical vortex, a light beam endowed with helical wavefronts. When focused, it appears as a ring of light whose radius depends on its helicity. The vortex ring carries orbital angular momentum, which it transfers to trapped particles, thus spinning them around. This work reports the unprecedented realization of a wide range of optical vortices and the study of their angular momentum content, as well as the introduction of two new classes of tunable optical vortices. The second half of this talk presents one of the first biophysical applications of HOT. A force sensing array of HOTs is employed to measure the elasticity of the pericellular matrix, a cross-linked biopolymer network attached to the outer membrane of cells. Ultimately, the micromechanics of the pericellular matrix will be correlated with its suspected role in modulating cell adhesion during critical events like mitosis, migration, and perhaps even cancer metastasis.