Gefördert durch:

Prof. Dr. Alexander Rohrbach

          

Bio- und Nano-Photonik, IMTEK, Universität Freiburg

Tel:     +49 761 203 7536

Email: rohrbach@imtek.uni-freiburg.de

homepage

 

Our goal is to understand the structure, dynamics, and mechanics of cells and biomaterials at the scale of the wavelength of light and below. Therefore we investigate measuring and manipulating techniques, such as

  • New laser scanning microscopy methods to optimize the interaction between light and matter
  • Optical tweezers including 3-D particle tracking at microseconds-speed and nanometer precision
  • Computer controled holographic illumination systems

We use these methods to investigate

  • Thermally fluctuating systems and phenomena in soft materials (cells and complex liquids)
  • The nanomechanics of molecular motors and the cytoskeleton

Our basic physical research serves as a platform for developing new technologies for the following fields of application. High-resolution microscopy for researching versatile cell, polymer, and surface structures: We improve optical resolution and contrast of 3-D images by intelligent combinations of diffraction-limited illumination of smallest structures (0.1 – 1 μm) and light scattered at the object to be studied. Here one distinguishes between light carrying relevant object information and light carrying no or wrong information.

 

Measuring and structuring nanotechnology: How do you build something that is so small that you cannot even see it under a microscope? By using laser optical tweezers (optical traps) we try to assemble the smallest structures of spherical or rod-shaped building blocks. These are smaller than 0.1 μm and are typically metals or semi-conductors, meaning they have multiple functional properties. We utilize new measuring techniques, such as optically trapped and guided probes or holographic interference, to optically measure and “see” the assembled systems quickly and precisely.

 

Biophysics and biotechnology: Processes occurring in cells or at their membranes are not only determined by biochemical laws, but also by purely physical laws which regulate reaction kinetics or cell mechanics by diffusion, fluctuation, and molecular motors. This affects the generation and propagation of cellular signals and is one of the subjects of research in the Biological Signalling Studies (bioss) Cluster of Excellence. The fluctuation-controlled absorption of bacteria, viruses, and drugs through still unknown diffusion properties nearby cell membranes plays an important role in medicine and pharmaceutical research. We strive to understand these physical laws by investigating isolated cellular subsystems to find out how they react to specific changes in their environmental conditions.

 

Short CV

 

10 ausgewählte Publikationen:

  • Microscopy with self-reconstructing beams.
    Fahrbach, FOP, Simon P, Rohrbach A. 
    Nature Photonics 2010, 4, 11, 780-785
  • Improved interferometric tracking of trapped particles using two frequency detuned beams.
    Friedrich L, Rohrbach A.
    Optics Letters 2010, 35 (11): p. 1920–1922
  • Artifacts resulting from imaging in scattering media: a theoretical prediction.
    Rohrbach A.
    Optics Letters 2009, Vol. 34, No. 19, pp. 3041-4043
  • Filopodia act as phagocytic tentacles and pull with discrete steps and a load-dependent velocity.
    Kress H, Stelzer EHK, Holzer D, Buss F, Griffiths G, Rohrbach A. 
    Proc. Nat. Acad. Sci. 2007, Vol.104, 11633–11638
  • Switching and measuring a force of 25 femtoNewtons with an optical trap.
    Rohrbach A.
    Opt. Express 2005, 1324: p. 9696-9701
  • Stiffness of optical traps: Quantitative agreement between experiment and electromagnetic theory.
    Rohrbach A.
    Phys. Rev. Lett 2005, 95: p. 168102
  • Control of relative radiation pressure in optical traps: Application to phagocytic membrane binding studies.
    Kress H, Stelzer EHK, Griffiths G, Rohrbach A.
    Phys.Rev.E 2005, 71, 061927.
  • Three-dimensional bead position histograms reveal single-molecule nano-mechanics.
    Becker, N, Altmann S, Scholz TH, Hörber H,  Stelzer E,  Rohrbach A. 
    Phys.Rev.E 2005, 71, 021907.
  • Trapping and tracking a local probe with a Photonic Force Microscope.
    Rohrbach A, Tischer C, Neumayer D, Florin EL, Stelzer EHK.
    Rev. Sci. Instr. 2004, 75, 2197
  • Tilt angle dependent 3D-position detection of a cylindrical particle in a focused laser beam.
    Kress H, Stelzer EHK, Rohrbach A. 
    Appl.Phys.Lett. 2004, 84, 18, 4271