Dr. Ralf Zimmermann, researcher
Teresa Büttner, PhD student
Felix Schrön, PhD student
Susanne Bartsch, technician
Nelly Rein, technician



Understanding the electrostatic interactions of polymers in aqueous environments is one of the keys for the development of advanced biofunctional materials. To provide answers to fundamental questions on the mechanisms of the charge formation at bio-interfaces as well as to clarify interrelations between charge and structure of polymer materials we develop and apply complementary analytical techniques in combination with tailored models for interfacial charge formation and simulations.

Furthermore, strategies for unravelling the mechanisms of molecular transport in soft materials as well as new diagnostic principles are established.

Advanced electrokinetic methods

Electrokinetic and surface conductivity measurements provide valuable information about the charging and structure of polymers at interfaces. In order to use the versatile options of this approach, we developed the Microslit Electrokinetic Set-up. The instrument was further extended by implementing Reflectometric Interference Spectroscopy for the simultaneous determination of the optical layer thickness of polymer films and ATR-FTIR spectroscopy for assessing secondary structure variations of immobilized biopolymers as influenced by variations of the interfacial electrical charge.

Charging by unsymmetrical water ion adsorption

Charging of solid-liquid interfaces is an ubiquitous phenomenon of particular importance in surface and materials science. On many solid surfaces the charging is caused by ionization of functional groups, e.g., carboxyl or amino groups. However, also for surfaces without ionisable surface groups charging is observed in aqueous environments.

The phenomenon is often attributed to the unsymmetrical adsorption of hydroxide and hydronium ions. Despite of numerous theoretical and experimental studies, very little is known on the interaction of hydroxide and hydronium ions with water-hydrophobic interfaces. To address this question, we systematically perform electrokinetic measurements at various material surfaces.

Charge and structure at soft interfaces

Soft polymer coatings are widely applied in biomaterials science as they allow for tailoring of surface properties and implementation of advanced functional features into traditional materials. The optimization of the coating performance in biomedical and technical applications necessarily requires the measurement, analysis, and understanding of their physico-chemical properties.

We apply streaming current, surface conductivity and swelling measurements in combination with tailored models for the charging and electrokinetics at soft surfaces for a comprehensive characterization of the film charge and structure.

Ion-specific phenomena at bilayer lipid membranes

Cell membranes, the interfacial boundary the between intra- and extracellular space are complex systems and involved in many cell functions such
as signalling, protein sorting or apoptosis. At the MBC we use supported bilayer lipid membranes as model system that allow for a characterization
of cellular membranes in simpler and well defined environments and to study membrane protein functions.

Methods like electrokinetic measurements, fluorescence microscopy, and ATR-FTIR spectroscopy are applied to study the influence of charge
formation on the membrane formation, fluidity, structure, and stability.

Molecular transport in hydrogels

Biohybrid hydrogels consiting of electrically neutral synthetic polymers and highly anionic glycosaminoglycans offer exciting options for
regenerative therapies as they allow for the electrostatic conjugation of various growth factors. We work on the establishment of analytical
methods and models that provide insights into correlations between the molecular transport and the hydrogel composition and structure. These
 models are further used to predict the spatially and timely distribution of morphogens in cell culture experiments.


Microchannel flows constitute most part of the transport process in various Lab-On-Chip devices. At the micro- and nanometer size of structures in
these systems, transport processes are significantly affected by interfacial phenomena such as electrokinetic effects and surface roughness.
As the fabrication of chips with fine channels come into realize, people demand detailed understanding how material properties and chip design influence the transport in microchannels. At the MBC we apply analytical and theoretical approaches to better understand electrosurface phenomena in

Selected Publications

  • Zimmermann, R.; Duval; J.F.L.; Werner, C.:
    Probing biointerfaces: electrokinetics. In: Biointerfaces: Where Material meets Biology/ed. by D.W. Hutmacher and W. Chrzanowski. RSC Press 2015, Chapter 3, 55-73
  • Zimmermann, R.; Romeis, D.; Bihannic, I.; Chohen Stuart, M.; Sommer, J.-U.; Werner, C.; Duval, J.F.L.:
    Electrokinetic as an alternative to neutron reflectivity for evaluation of segment density distribution in PEO brushes. Soft Matter 10 (2014) 7804-7809
  • Zimmermann, R.; Dukhin, S.S.; Werner, C.; Duval, J.F.L.:
    On the use of electrokinetics for unravelling charging and structure of soft planar polymer films. Current Opinion in Colloid & Interface Science 18 (2013) 83-92
  • Zimmermann, R.; Bartsch, S.; Freudenberg, U.; Werner, C.:
    Electrokinetic analysis to reveal composition and structure of biohybrid hydrogels. Analytical Chemistry 84 (2012) 9592-9595
  • Zimmermann, R.; Küttner, D.; Renner, L.; Kaufmann, M.; Werner, C.:
    Fluidity modulation of phospholipid bilayers by electrolyte ions: Insights from fluorescence microscopy and microslit electrokinetic experiments. Journal of Physical Chemistry / A: Molecules, spectroscopy, kinetics, environment & general theory 116 (2012) 6519-6525
  • Duval, J. F. L.; Küttner, D.; Werner, C.; Zimmermann, R.:
    Electrohydrodynamics of soft polyelectrolyte multilayers: point of zero-streaming current. Langmuir 27 (2011) 10739-10752
  • Duval, J. F. L.; Küttner, D.; Nitschke, M.; Werner, C.; Zimmermann, R.:
    Interrelations between charging, structure and electrokinetics of nanometric polyelectrolyte films. Journal of Colloid and Interface Science 362 (2011) 439-449
  • Zimmermann, R.; Kuckling, D.; Kaufmann, M.; Werner, C.; Duval, J. F. L.:
    Electrokinetics of a poly(N-isopropylacrylamide-co-carboxyacrylamide) soft thin-film. Evidence of segment distribution in the swollen state. Langmuir 26 (2010) 18169-18181
  • Zimmermann, R.; Freudenberg, U.; Schweiß, R.; Küttner, D.; Werner, C.:
    Hydroxide and hydronium ion adsorption - A survey. Current Opinion in Colloid and Interface Science 15 (2010) 196-202
  • Zimmermann, R.; Osaki, T.; Gauglitz, G.; Werner, C.:
    Combined microslit electrokinetic measurements and reflectometric interference spectroscopy to study protein adsorption processes. Biointerphases 2 (2007) 159-164


  • Microslit Electrokinetic Set-Up (MES): in-house developed instrument to analyze the electrical charging of interfaces and infer on the structural features of polymer films
  • Quarz Crystal Microbalance (Q-Sense E4)
  • Spectroscopic Ellipsometer M-2000 (J. A. Woollam Co., Inc.)
  • VIS spectrometer Specol 1100 (Analytic Jena) for Reflectometric interference Spectoscopy (RlfS) at interfaces (can be optionally used in combination with the MES)
  • FTIR spectrometer Equinox 55 (Bruker) with SBSR-Unit (OTISPEC) for ATR-FTIR spetroscopy at
  • Video-based optical contact angle meter OCA 30 (Dataphysics)


Group members

Dr. Jens Friedrichs, researcher
Dr. Ralf Helbig, researcher
Julia Nickerl, PhD student
Nicole Träber, PhD student

Research focus

Adhesive interactions of cells with (bio)materials trigger a multitude of desired, but also undesired processes. On one hand, these interactions can induce signalling pathways that are involved in regulating important cellular processes including cell migration, gene expression, cell survival, tissue organization, and differentiation. On the other hand, the deposition of microorganisms and their extracellular polymeric substrates on material surfaces can lead to significant health risks and financial losses in medical, marine and industrial fields.

We focus on the development of faithfully designed, biomimetic (bio)polymer matrices to control and guide adhesive interactions. Furthermore, we apply atomic-force microscopy-based methods to characterize the structure and function of these matrices.

Reconstitution of bioartificial basement membrane-like matrices for cell culture and tissue engineering

Basement membranes are specialized extracellular matrices that have important roles in cell attachment, migration, growth, and differentiation. Recent advancements in bioengineering result in a strong demand for bioartificial in vivo-like, basement membrane-mimicking environments. We reconstitute highly defined and immobilized bioartificial basement membrane-like matrices from combinations of recombinant extracellular matrix proteins using cell-produced basement membranes as blueprints. The bioartificial basement membrane-like matrices developed find application in advanced cell culture studies and in tissue engineering.


Adhesive interactions of cells with their environment can trigger a multitude of desired, but also undesired processes. An undesired, adhesion-associated process is the deposition of microorganisms and their extracellular polymeric substrates on man-made surfaces, so called biofouling or biofilm formation. This phenomenon can occur in an extremely wide range of situations, from the colonization of medical- and process devices to the production of ultra-pure, drinking and process water and the fouling of ship hulls, pipelines and reservoirs. In this context we focus on the development, characterization and application of well-characterized surfaces with antifouling properties. More precisely, we investigate the influence of biofilm-degrading enzymes, covalently immobilized onto maleic anhydride copolymer films, on the adhesion of major marine foulers and bacteria associated with hospital-acquired infections.

Biomimetic, omniphobic surfaces

Natural surfaces often possess amazing shapes and structures that arouse interest for both basic research and commercial applications. A pertinent example is the skin of springtails (Collembola) that features mechanically stable, hierarchical, micro- to nanoscale structural elements that equips the animal with omniphobic, anti-adhesive properties. We focus on characterizing the skin of springtails and recapitulate their robust and effectively repellent surface characteristics. Furthermore, we deduce design principles for non-wetting and antifouling surfaces from the structural and chemical features of the skin.

Current activities

  • Theoretical models for wetting transition on complex shaped surface features
  • Mimicking the omniphobic characteristics by polymer membranes
  • Chemical characterization of the skin
  • Bacterial adhesion tests on synthetic surfaces mimicking structure and chemistry of the springtail skin




Cause and consequence of adhesive interactions of hematopoietic stem cells and leukemic cells

Blood homeostasis is dependent on the numerous interactions between primitive blood cells and the different cell types present in the bone marrow as well as the extracellular matrix. We apply AFM-based single-cell force spectroscopy (SCFS) to quantify the interactions between hematopoietic stem and progenitor cells (HSPC) as well leukemic cells and (i) cell types present in the bone marrow (i.e. multipotent mesenchymal stromal cells [MSCs], osteoblasts and endothelial cells), (ii) a set of defined decellularized extracellular matrices (derived from MSC cultures and (iii) engineered (bio)polymer matrices)

Selected publications

  • Reichert, D.;  Friedrichs, J.;  Ritter, S.; Käubler, T.;  Werner, C.; Bornhäuser, M.;  Corbeil, D.:
    Phenotypic, morphological and adhesive differences of human hematopoietic progenitor cells cultured on murine versus human mesenchymal stromal cells. Scientific Reports 5, Article number: 15680 (2015) doi:10.1038/srep15680
  • Prewitz, M.; Stißel, A.; Friedrichs, J.; Träber, N.; Vogler, S.; Bornhäuser, M.; Werner, C.:
    Extracellular matrix deposition of bone marrow stroma enhanced by macromolecular crowding. Biomaterials 73 (2015) 60-69
  • Hensel, R.; Neinhuis, C.; Werner, C.:
    Omniphobic characteristics of animals in aqueous or temporarily flooded habitats and their applications. Chemical Society Reviews 2015, Doi:10.1039/c5cs00438a
  • Friedrichs, J.; Werner, C.:
    Polymeric coatings to fight biofouling. In: Encyclopedia of Polymeric Nanomaterials: Antifouling and antimicrobial polymeric coatings/ed. by S. Kobayashi and K. Müllen. Springer Verlag Berlin, Heidelberg, 2015, 1944-1950
  • Fischer, M.; Vahdatzadeh, M.; Konradi, R.; Friedrichs, J.; Maitz, M.; Freudenberg, U.; Werner, C.:
    Multilayer hydrogel coatings to combine hemocompatibility and antimicrobial activity. Biomaterials 56 (2015) 198-205
  • Bray, L.; Binner, M.; Holzheu, A.; Friedrichs, J.; Freudenberg, U.; Hutmacher, D.W.; Werner, C.:
    Multi-parametric hydrogels support 3D in vitro bioengineered microenvironment models of tumour angiogenesis. Biomaterials 59 (2015) 609-620
  • Hensel, R.; Finn, A.; Helbig, R.; Killge, S.; Braun, H.-G.; Werner, C.:
    In situ experiments to reveal the role of surface feature sidewalls in the Cassie-Wenzel transition. Langmuir 30 (2014) 15162-15170
  • Nickerl, J.;Tsurkan, M.; Hensel, R.; Neinhuis, C.; Werner, C.:
    The multi-layered protective cuticle of Collembola: A chemical analysis. Journal of the Royal Society Interface 11 (2014) 20140619
  • Schubert, R.; Strohmeyer, N.; Bharadwaj, M.; Ramanathan, S.P.; Krieg, M.; Friedrichs, J.; Franz, C.M.; Müller, D.J.:
    Assay for characterizing the recovery of vertebrate cells for adhesion measurements by single-force spectroscopy. FEBS Letters 588 (2014) 3639-3648
  • Welzel, P.; Friedrichs, J.; Grimmer, M.; Vogler, S.; Freudenberg, U.; Werner, C.:
    Cryogel micromechanics unraveled by atomic force microscopy-based nanoindentation. Advanced Healthcare Materials 3 (2014) 1849-1853
  • Hensel, R. et al.:
    Biologically inspired omniphobic surfaces by reverse imprint lithography. Advanced Materials 26 (2014) 2029-2033
  • Arnold, G.; Schade, E.; Schneider, Y.; Friedrichs, J.; Babick, F.; Werner, C.; Rohm, H.:
    Influence of individual phospholipids on the physical properties of oil-based suspensions. Journal of thr American Oil Chemists' Society 91 (2014) 71-77
  • Hensel, R.; Helbig, R.; Aland, S.; Voigt, A.; Neinhuis, C.; Werner, C.:
    Tunable nano-replication to explore the omniphobic characteristics of springtail skin. NPG Asia Materials 5 (2013), e37
  • Hensel, R.; Helbig, R.; Aland, S.; Braun, H.-G.; Voigt, A.; Neinhuis, C.; Werner, C.:
    Wetting resistance at its topographical limit – The benefit of mushroom and serif T structures. Langmuir 29 (2013) 1100-1112
  • Prewitz, M. et al.:
    Tightly anchored tissue-mimetic matrices as instructive stem cell microenvironments. Nature Methods 10 (2013) 788-794
  • Teräväinen, T.P. et al.:
    ∝V-Integrins are required for mechanotransduction in MDCK epithelial cells. PLoS ONE 8 (2013) e71485
  • Friedrichs, J.; Werner, C.; Müller, D.J.:
    Quantifying cellular adhesion to covalently immobilized extracellular matrix proteins by single-cell force spectroscopy. Methods Mol Biol 1046 (2013) 19-37
  • Friedrichs, J.; Zieris, A.; Prokoph, S.; Werner, C.:
    Quantifying the effect of covalently immobilized enzymes on biofilm formation by atomic force microscopy-based single-cell force spectroscopy. Macromolecular Rapid Communications 33 (2012) 1453-1458
  • Helbig, R.; Nickerl, J.; Neinhuis, C.; Werner, C.:
    Smart skin patterns protect springtails. PLoS ONE 6 (2011) e25105
  • Friedrichs, J.; Helenius, J.; Müller, D.J.:
    Quantifying cellular adhesion to extracellular matrix components by single-cell force spectroscopy. Nature Protocols 5 (2010) 1353-1361
  • Friedrichs, J.; Manninen, A.; Müller, D.J.; Helenius, J.
    Galectin-3 regulations integrin alpha2beta1-mediated adhesion to collagen -I und -IV. J Biol Chem 283 (2008) 32264-32272
  • Taubenberger, A. et al.:
    Revealing early steps of 2 1 integrin-mediated adhesion to collagen type I by using single-force spectroscopy. Mol Biol Cell 18 (2007) 1634-1644


  • Nanowizard I atomic force microscope (JPK Instruments) mounted on an inverted optical microscope (Zeiss Axio Observer. A1)
  • Nanowizard II atomic force microscope (JPK Instruments) mounted on an inverted optical microscope (Zeiss Axio Observer.D1) equipped with a CellHesion Module (extended z-range of 100 µm), temperature-controlled sample stages (BioCell, PetriDish Heater and a Heating-Cooling Stage), a kelvin probe and scanning capacitance microscopy module and a top-view optic.

    Examples of application:
  • Polymer and thin film imaging
  • Imaging of functionalized surfaces
  • (Live) cell imaging
  • Single-cell force spectroscopy (Cell adhesion)
  • Nanoindentation measurements on biological and non-biological samples
  • Binding studies e.g. antibody/antigen, receptor/ligand
  • UV-Imprint lithography (PFPEdma templates)
  • Soft lithography (PDMS templates)
  • Optical Surface Analysis (Nanofocus μsurf explorer)
  • Contact Angle System (Dataphysics OCA 30)