报告题目：Light microrobotics in biophysics
报 告 人：Pál Ormos（Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences）
Pál Ormos received his MS degree in physics in 1975 atthe University of Szeged, Hungary. He is working in the Institute of Biophysics, Biological Research Centre (BRC) of the Hugarian Academy of Sciences, Szeged.
Currently he is director general of BRC. During his career his activity spanned different areas of biological physics, from protein dynamics through the physics of biological energy transduction, presentlyhis interest is directed towards single particle biophysics studied by optical micromanipulation – with emphasis on the development of the optical manipulation technique. He is elected fellow of the American Physical Society, member of the American Biophysical Society.
In the basic scheme of optical micromanipulation a focussed Gaussian light beam traps a spherical object defining its position. Since typically objects of micrometer size are grabbed by pN forces, the method is extremely useful in the study of biological objects. The possibilities can be vastly extended if the trapping light is structured and the object has appropriate non trivial shape. Key components of the procedure are the generation of structured trapping light field and the fabrication of complex shaped microparticles and the generation of structured trapping light field.
Beam shaping is achieved by the use of Spatial Light Modulators (SLM), freely configurable optical traps actuated in real time are generated.
Two-photon excitation induced photopolymerization is the method to produce particles with shapes of unlimited complexity, generating micrometer sized objects to be manipulated: microtools, models of biological objects etc. By the combination of these technologies complex manipulation schemes can be realized, creating a new field of light robotics.
I will show characteristic examples to illustrate the possibilities.
The grabbed objects can be oriented, rotated, creating an optical wrench that enables the measurement of the torsional properties of biological micromolecules. With the help of the light actuated microtools one can determine local mechanical properties of biological objects, local fluorescence or Raman excitation with submicrometer resolution can be achieved using plasmonic excitation mediated by appropriate microtools. The indirect optical manipulation of live cells with the help of the manipulators enables the separation of the trapping light from the trapped object, thus preventing light damage of the cells, so that a prolonged investigation becomes possible.
Optically manipulated microparticles also offer excellent model systems to study biological motion in a well-controlled manner, in detail not possible on native systems. Two examples will be discussed: Hydrodynamic synchronization and quasy-autonomous moving robots driven by light.