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 
Peter Debye Institute for Soft Matter Physics
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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