Optical Tweezers
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Optical micromanipulation makes use of the fact that light carries energy and momentum, and sometimes even angular momentum. This allows one to build micro-tools of pure light which are able to catch, hold, move or stretch µm-size particles with pN forces. We use Spatial Light Modulators (SLMs) to holographically shape optical traps. In the past we have realized dual-beam fiber optical traps, 2D or 3D arrays of trapping beams (operating in the Fourier or in the Fresnel regime), doughnut-shaped trapping beams which carry optical angular momentum and line traps of arbitrary shape Recently we have developed a large-range mirror-trap, the Optical "Macro-Tweezers" system which is suitable to trap large and fast microorganisms. Adding an ultrasonic standing wave in a combined acoustic and optical trap we have a "best of both worlds scenario" with strong acoustic levitation and flexible and precisely controllable optical manipulation (see Topics below). |
Projects
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Direct measurement of optical forces and torque with optical tweezers |
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Speeding up SLMs with overdrive |
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Optical "Macro-Tweezers" |
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Combined acoustic and optical trap |
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Holographic trapping patterns |
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Optical force measurements on pulmonary surfactant |
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Self-regularization in dual beam fiber traps |
Moreover, we also use optical traps to hold specimens in place for quantitative phase microscopy.
Collaborations:
- With Gijs Wuite and Erwin Petermann from the Vrije Universiteit Amsterdam:
Sitters, G., Kamsma, D., Thalhammer, G., Ritsch-Marte, M., Peterman, E. J., & Wuite, G. J.. Acoustic force spectroscopy. Nature methods, 12(1), 47-50 (2015).
- With Helmut Ritsch for the Institute of Theoretical Physics at the University of Innsbruck on the theory of optical forces on and in extended dielectric objects
M. Sonnleitner, M. Ritsch-Marte, and H. Ritsch: Optical forces, trapping and strain on extended dielectric objects, Europhys. Lett., 94, 34005 (2011).
- With Miles Padgett(University of Glasgow):
R. Bowman, A. Jesacher, G. Thalhammer, G. Gibson, M. Ritsch-Marte, and M. Padgett: Position clamping in a holographic counterpropagating optical trap, Optics Express 19, 9908-9914 (2011) [Selected for the Virtual Journal for Biomedical Optics 6 (6), July 2011].
- With Paul Dietl (Ulm University) and Thomas Haller (Physiology Department, Innsbruck Medical University) on pulmonary surfactant:
W. Singer, M. Frick, Th. Haller, S. Bernet, P. Dietl, M. Ritsch-Marte: Mechanical forces impeding exocytotic surfactant release revealed by optical tweezers, Biophys. J. 84, 1344-1351 (2003).