Optical manipulation – Holographic optical Tweezers (HOT)
Optical tweezers enable to confine a microscopic object of nano- or micrometers and move it precisely. Many applications, however, require the ability to control more than one object simultaneously. Holographic optical tweezers (HOT) elegantly extend the basic principle of optical tweezers towards the optical control of a multitude of particles. For this purpose, a spatial light modulator (SLM) modulates the phase-front of a laser light field by means of computer-generated holograms (Figure (a)) in order to create several single tweezers in the microscopic sample at the same time (Figure (b)).
The use of multiple dynamic optical traps is of tremendous advantage if a precise manipulation and three-dimensional control of several (non-spherical) objects is necessary, for example in order to rotate the object into a defined orientation and align it arbitrarily (Figure (c)). In particular, we use the outstanding capabilities of HOT for the organization of nanocontainers, as e.g. zeolite L which allow supramolecular organization of their guest molecules (in collaboration with AG Studer) [1,2], and the manipulation of microprobes and microtools for the intra- and extracellular probing of the bio-mechanical properties of living cells  (.bio). In addition to established HOT, we assess systematically sophisticated structured light fields for tailored 3d optical trapping of different types of particles (.complex). Moreover, we have demonstrated the creation of optical bottle beams and subsequent trapping of absorbing particles in air as well as the optofluidic manipulation of droplets (.fluid).
 Dynamic and reversible organization of zeolite L crystals induced by holographic optical tweezers M. Woerdemann, S. Gläsener, F. Hörner, A. Devaux, L. De Cola, C. Denz Advanced Materials 22, 2010, 4176-4179.
 Managing hierarchical supramolecular organization with holographic optical tweezers OPN M. Woerdemann, A. Devaux, L. De Cola, C. Denz, Optics in 2010, 2010, 21, 40.
 Three-Dimensional Exploration and Mechano-Biophysical Analysis of the Inner Structure of Living Cells, Á. Barroso, M. Woerdemann, A. Vollmer, G. von Bally, B. Kemper, C. Denz Small 9, 2013, 885-893.