Soft Matter Physics Division - Biophysics at the University of Leipzig University of Leipzig
PeopleStaff MembersProf. Dr. Josef A. Käs
Prof. Dr. Josef A. Käs
Principal Investigator & Head of the Soft Matter Physics Division
University of Leipzig
Faculty of Physics and Earth Science 
Institute for Experimental Physics I
Soft Matter Physics Division
Linnéstraße 5, 04103 Leipzig, Germany
(+49 341) 97 32471
(+49 341) 97 32479
1990 Diplom Physics, Technische Universität München, advisor: E. Sackmann
1993 Dr. rer. nat., Physics, Technische Universität München, advisor: E. Sackmann
Professional Postions
1993 - 1996 Postdoctoral Fellow Harvard, advisor: P. Janmey
08/1996 - 10/2000 Assistant Professor, Department of Physics, University of Texas at Austin
08/1996 - 05/2002 Member, Institute for Cellular and Molecular Biology, Univ. of Texas
08/1996 - 05/2002 Member, Center for Nonlinear Dynamics, University of Texas at Austin
07/2000 - 05/2002 Steering comittee, Center for Nano and Molecular Science, Univ. of Texas
10/2000 - 05/2002 Associate Professor, Dept. of Physics, Univ. of Texas (early tenure)
10/2001 - present Chair, scientific advisory board, Evacyte Inc.
03/2001 Offer, C4-professorship, University of Leipzig ("Ruf, C4 Nachfolge Klose")
07/2001 Offer, Endowed Chair, Department of Physics, University of Texas at Austin
08/2001 Offer, C4- professorship, Friedrich-Schiller Universitaet Jena ("Ruf, C4-Biophysik")
05/2002 - present C4-Professor, University of Leipzig, Director Institute of Soft Matter Physics
08/2002 - present Adjunct Professor, Dept of biomed. Eng., Univ. of Texas at Austin
08/2008 - 05/2016 Head of the Institute for Experimental Physics I 

  • 1999 - 2000, ICMB Fellow, Institute of Molecular and Cell Biology, UT Austin
  • 2000 - 2001, ICMB Fellow, Institute of Molecular and Cell Biology, UT Austin
  • 2001 - 2002, ICMB Fellow, Institute of Molecular and Cell Biology, UT Austin
  • 2000 - 2003, Distinguished Lecturer, SigmaXi
  • 2001 Wolfgang Paul Prize awarded by the Humboldt Foundation
  • US Patent No. 6,067,859 "Optical Stretcher" (May 30, 2000). Inventors: Josef Käs and Jochen Guck. Also the European and Asian patents are awarded.
  • US Patent No. 7,435,568 "Optical Cell Guidance Method and Apparatus". Inventors: Josef Käs, Mark Raizen, Timo Betz and Allen Ehrlicher. The European and Asian patents are pending
Research Interests and Expertise
  • laser physics, optics, scanning probe techniques
  • biological physics, condensed matter physics of soft matter, polymer physics, medical physics, and nonlinear dynamics
  • cell and molecular biology, neuroscience, oncology, genetics, regenerative medicine
  • optical imaging of the motions of individual polymer chains in polymer networks with nano-scale resolution, development of novel laser traps, AFM-based microrheology, use of nanoparticles (quantum dots, gold colloids) as probes and manipulation tools, optical guidance of neurons
Selected Publications
  • J. Käs, E. Sackmann: Shape transitions and shape stability of giant phospholipid vesicles in pure water induced by area-to-volume changes, Biophys. J., 60, 825-844 (1991)
  • J. Käs, H. Strey, E. Sackmann: Direct imaging of reptation for semiflexible actin filaments, Nature, 368, 226-229 (1994)
  • F. C. MacKintosh, J. Käs, P. A. Janmey: Elasticity of semiflexible biopolymer networks, Phys. Rev. Lett., 75(24), 4425-4428 (1995)
  • J. Käs, H. Strey, J. X. Tang, D. Finger, R. Ezzell, E. Sackmann, P. A. Janmey: F-actin, a model polymer for semiflexible chains in dilute, semidilute and liquid crystalline solutions, Biophys. J., 70, 609-625 (1996)
  • J. Guck, R. Ananthakrishnan, T. J. Moon, C. C. Cunningham, J. Käs: Optical deformability of soft dielectric materials, Phys. Rev. Lett., 84(23), 5451-5454 (2000)
  • R. Mahaffy, C. K. Shih, F. C. MacKintosh, J. Käs: Scanning probe-based, frequency-dependent microrheology of polymer gels and biological cells, Phys. Rev. Lett., 85(4), 880-883 (2000)
  • M. Forstner, J. Käs, D. Martin: Single lipid diffusion in Langmuir monolayers, Langmuir, 17(3), 567-570 (2001)
  • J. Guck, R. Ananthakrishnan, T.J. Moon, C. C. Cunningham, J. Käs: The optical stretcher - a novel, noninvasive tool to manipulate biological materials, Biophys. J., 81 767-784 (2001)
  • D. Humphrey, C. Duggan, D. Saha, D. Smith, J. Käs: Active fluidization of polymer networks through molecular motors, Nature, 416, 413-416 (2002)
  • A. Ehrlicher, T. Betz, B. Stuhrmann, D. Koch, V. Milner, M. Raizen, J. Käs: Guiding neuronal growth with light, Proc. Natl. Acad. Sci., 99(25) 16024-16028 (2002)
  • M. Forstner, D. Martin, A. M. Navar, J. Käs: Simultaneous single-particle tracking and visualization of domain structures on lipid monolayers, Langmuir, 19, 4876-4879 (2003)
  • R. Mahaffy, C. K. Shih, F. C. MacKintosh, J. Käs: Quantitative analysis of the viscoelastic properties of thin regions of fibroblasts using atomic force microscopy, Biophys. J., 86, 1777-1793 (2004)
  • Stuhrmann, M. Gögler, T. Betz, A. Ehrlicher, D. Koch, J. Käs: Automated tracking and laser micromanipulation of motile cells, Review of Scientific Instruments, 76:035105 1-8 (2005)
  • J. Guck, H. Erickson, R. Ananthakrishnan, D. Mitchell, M. Romeyke, S. Schinkinger, F. Wottawah, B. Lincoln, J. Käs, S. Ulvick, C. Bilby: Optical Deformability as Inherent Cell Marker for Malignant Transformation and Metastatic Competence, Biophys. J. 88:5 (2005)
  • T. Betz, J. Teipel, D. Koch, W. Härtig, J. Guck, J. Käs, H. Giessen: Excitation beyond the monochromatic laser limit: Simultaneous 3-D confocal and multiphoton microscopy with a tapered fiber as white-light laser source, J Biomed Optics, in press (2005)
  • F. Wottawah, S. Schinkinger, B. Lincoln, R. Ananthakrishnan, M. Romeyke, J. Guck, J. Käs: Optical rheology of biological cells, Phys. Rev. Lett., 94(9), 98103 (2005)
University of Leipzig  |  Faculty of Physics and Earth Sciences  |  Institute of Experimental Physics I
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