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Welcome to the Bio- and Nano-Photonics research group

Head of the Laboratory


Prof. Dr. Alexander Rohrbach

Email: rohrbach(at)imtek.de

University of Freiburg
Department of Microsystems Engineering - IMTEK
Laboratory for Bio- and Nano-Photonics
Georges-Köhler-Allee 102
79110 Freiburg
TEL. ++49 761 203 7536
TEL. ++49 761 203 7548 (secretary)


Research goals

Living cells are fascinating microsystems driven by a variety of physics principles. Therefore we develop novel laser optical microscopy and optical force based applications, to investigate the biophysics of living cells and of bio-mimetic systems based on their nano-mechanics and thermal fluctuations. These approaches will help us to better understand e.g. infection diseases.


Our research group


Please click here for alternative group picture

... and in action  
  Who said working in a lab isn't fun? Click on the video to see us doing our business!  
Recent research highlights:  
100nm virus dummies on cell Click on the preview for the enlarged movie of a live macrophage cell (with several filopodia = "cell fingers") in contact with dozens of highly dynamic 100nm small corona virus dummies: 100 Hz ROCS microscopy images (left). Right half: edge enhancement.


Special featured publication:

Get rid of the effects of diffusive photons! Consider not only the optical PSF, but also the object PSF, which changes with depth !


Meinert,T., ..., Rohrbach, A.

Separation of ballistic and diffusive fluorescence photons in confocal Light-Sheet Microscopy of Arabidopsis roots

Scientific reports 6, 30378 (2016).


Selected Publications


Ayala, Y. A., R. Omidvar, W. Römer and A. Rohrbach
Thermal fluctuations of the lipid membrane determine particle uptake into Giant Unilamellar Vesicles.
Nature Communications. 2023

F. Jünger, D. Ruh, D. Strobel, R. Michiels, D. Huber, ... A: Rohrbach
100 Hz ROCS microscopy correlated with fluorescence reveals cellular dynamics on different spatiotemporal scales
Nature Communications 2022; 13(1): 1758

Landenberger B, Yatish, Rohrbach A.
Towards non-blind optical tweezing by finding 3D refractive index changes through off-focus interferometric tracking.
Nature Communications. 2021;12(1):6922.

L. Friedrich, A. Rohrbach
Surface imaging beyond the diffraction limit with optically trapped spheres
Nature Nanotechnology 2015, issue 10, pages 1064–1069

M. Koch, A. Rohrbach
Object adapted optical trapping and shape tracking of energy switching helical bacteria
Nature Photonics 2012, issue 6, pages 680 - 686

F. Fahrbach, A. Rohrbach
Propagation stability of self-reconstructing Bessel beams enables contrast-enhanced imaging in thick media
Nature Communications 2012, issue 3, page 632

F. Fahrbach, P. Simon, A. Rohrbach
Microscopy with self-reconstructing beams
Nature Photonics 2010 , issue 4, pages 780 - 785

H. Kress, E. H. K. Stelzer, D. Holzer, F. Buss, G. Griffiths, A. Rohrbach
Filopodia act as phagocytic tentacles and pull with discrete steps and a load-dependent velocity
PNAS 2007, issue 104, pages 11633 - 11638

A. Rohrbach
Stiffness of optical traps: Quantitative agreement between experiment and electromagnetic theory
PRL 2005, issue 95, pages 168102



A paper by us was published in Small: "Making Hidden Cell Particle Interactions Visible by Thermal Noise Frequency Decomposition"

Ten people from our group flew to the amazing city of Porto (Portugal), to attend the world-largest conference on Microscopy.


Another paper accepted in Nature Communications: how thermal membrane fluctuations can predict particle uptake.

Frederik Görlitz starts as a new Postdoc in our group.

A paper by us about a multistep retraction process of filopodia was published in the Biophysical Journal: "Pulling, failing, and adaptive mechanotransduction of macrophage filopodia" (>>> download pdf)

Nearly the whole group went to the lovely city of Regensburg, and had a good and stimulating conference on biophysics & techniques.

A paper by us about applications of super-resolving rotating coherent scattering (ROCS) microscopy was published in Nature Communications

A paper by us about a new optical tweezers concept was published in Nature Communications

Meelad Lalenejad starts as a new PhD student in our lab working on novel light-sheet microscopy techniques.

Arash Felekary starts as a new PhD Student in our lab working on nanotube formation in heart cells.

Alexander Rohrbach gives an interview on imaging and analyzing the binding of viruses with ROCS microscopy. Podcast

Dominik Huber starts as a new PhD Student in our lab working on imaging viruses and particulate matter.

New Paper published in Communications Physics by Koebele & Rohrbach: "Shape-switch-block - Confocal light-sheet microscopy with sectioned Bessel beams and stimulated emission depletion". See Special collection in Nature !

A new research project ("Adaptive interferometric light-sheets
for resolution enhanced imaging with and without labeling") is funded by the Deutsche Forschungsgemeinschaft

Subhro Ghosh starts as a new Post-Doc in our lab working on molecular friction.

Yatish starts as a new PhD student in our lab working on novel light-sheet microscopy techniques.

A new research project ("The influence of particulate matter properties on the biophysical entry mechanisms into lung cells") is funded by the Deutsche Forschungsgemeinschaft

We are part of the DFG Sonderforschungsbereich SFB 1425 - Heterocellular Nature of Cardiac Lesions: Identities, Interactions, Implications! with project P11 ("Nano-Structural Basis for Mechanical Fibroblast-Cardiomyocyte Cross-Talk"). More info here: https://www.sfb1425.uni-freiburg.de/

New textbook "Wavefront Shaping for Biomedical Imaging" is published by Cambridge University Press and comprises a chapter about lightsheet microscopy by Alexander Rohrbach.

Alexander Rohrbach explains applications of optical tweezers in German television (3sat science documentary). >>> Link to 3sat media library,contribution starts at 6:42 min.

Rebecca Michiels successfully defended her PhD thesis. Congratulations!

New publication by Tobias Meinert in Biomedical Optics Express: "Light-sheet microscopy with adaptive Bessel beams" (>>> download pdf)

In honour of the recently awarded Nobel prize in physics, Alexander Rohrbach gives a talk about optical tweezers and ultrashort laser pulses, entitled "Manipulationen mit Licht: Von Laserfoki und Optischen Pinzetten". The talk takes place in the lecture hall of the physics department (13.12.2018; 17:15 o'clock) and is organized by the jDPG (junge DPG) Freiburg.

M.Sc. Niclas Trube, whose Master thesis was partly supervised by A. Rohrbach, has been awarded the Young Scientists Award at the Human Modeling Symposium 2018. Congratulations!

New publication by Dominic Ruh in Optica: "Superior contrast and resolution by image formation in rotating coherent scattering (ROCS) microscopy" (>>> download pdf)

Tetiana Udod starts as a new PhD student in our lab.

Dr. Tobias Meinert has been awarded the Wolfgang-Gentner-award for young scientists, thanks to outstanding achievements in his PhD thesis. Congratulations!

New publication by Hamideh Kermani in ACS Photonics: "Orientation-control of two plasmonically-coupled nanoparticles in an optical trap" ( >>> download pdf)

New publication by Felix Jünger in Cytoskeleton: "Strong cytoskeleton activity on millisecond timescales during particle binding and uptake revealed by ROCS microscopy" ( >>> download pdf)

New publication by Anjan Bhat Kashekodi in Biomedical Optics Express: "Miniature scanning light-sheet illumination implemented in a conventional microscope" ( >>> download pdf)

New publication by Julian Roth in Biophysical Journal: "Dynamics of a Protein Chain Motor Driving Helical Bacteria under Stress" ( >>> download pdf)

New publication by Matthias Koch in Biophysical Journal: "Label-free Imaging and Bending Analysis of Microtubules by ROCS Microscopy and Optical Trapping" ( >>> download pdf)

Tobias Meinert successfully defended his PhD thesis. Congratulations!



Keywords / Schlüsselwörter


Optics, Photonics, Biophysics, optical traps, optical tweezers, particle tracking, microscopy, light-sheet, self-reconstructing beams, Bessel beams, light propagation, BPM, scattering, superresolution, TIRF, fluorescence, STED, hydrodynamic coupling, fluctuation, diffusion, molecular motors, mechanics of the cytoskeleton, visco-elastic theory, phagocytes, filopodia, bacteria, cell wall, vesicles


Optik, Photonik, Biophysik, optische Fallen, optische Pinzetten, Partikeltracking, Mikroskopie, Lichtscheibe, selbstrekonstruierende Strahlen, Bessel-Strahlen, Lichtpropagation, BPM, Streuung, Superauflösung, TIRF, Fluoreszenz, STED, hydrodynamische Kopplung, Fluktuation, Diffusion, molekulare Motoren, Zytoskelett-Mechanik, Visko-elastische Theorie, Fresszellen, Filopodien, Bakterien, Zellwand, Vesikel















Bio- and Nanophotonics


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