Scientific CV Hans-Jürgen Butt
2016 How water advances on superhydro¬pho¬bic surfaces
Using confocal microscopy we image water drops advancing on a superhydrophobic array of micropillars. In contrast to common belief, the liquid surface gradually bends down until it touches the top face of the next micropillars. The apparent advancing contact angle is 180°. On the receding side, pinning to the top faces of the micropillars determines the apparent receding contact angle. We propose that the apparent receding contact angle should be used for characterizing superliquid-repellent surfaces rather than the apparent advancing contact angle and hysteresis (Schellenberger, Encinas, Vollmer, Butt, Phys. Rev. Lett.2016, 116, 096101. Highlighted by Nature Materials 2016, 15, 376).
Surfactants reduce dynamic receding contact angle
We demonstrate that even low amounts of surfactants (<10% CMC) drastically reduce the dynamic receding contact angle of aqueous solutions. The effect is independent on the type of surfactant and primarily depends on the concentration scaled by the critical micelle concentration (CMC) (Henrich, Truszkowska, Weirich, Anyfantakis, Nguyen, Wagner, Auernhammer & Butt. Soft Matter2016, 12, 7782-7791).
Surface force at high pressure
To measure surface forces at a pressure which exists in deep sea, we designed an optical trapping setup that allowed us to explore the interaction of a micrometer-sized glass bead and a solid glass wall up to 1 kbar. We demonstrated that the Debye length in aqueous electrolyte remained constant within approximately ±1 nm for salt concentrations of 0.1 and 1 mM (Pilat, Pouligny, Best, Nick, Berger & Butt, Phys. Rev. E.2016, 93, 022608).
2015 Homogeneous nucleation of ice confinement
When cooling water confined in nanoporous alumina it crystallizes by homogeneous rather than heterogeneous nucleation. The nucleation mechanism of water can be regulated by confinement within nanoporous alumina. We found a transition from heterogeneous nucleation of ice to homogeneous nucleation with decreasing pore diameter. Homogeneously nucleated ice in confinements seems to have a cubic rather than the usual hexagonal structure (Suzuki, Duran, Steinhart, Kappl, Butt & Floudas, Nano Letters 2015, 15, 1987-1992).
We use superamphiphobic surface to fabricate supraparticles by drying dispersions of nanoparticles. Such supraparticles can be used to photocatalysis (Wooh, Huesmann, Nawaz Tahir, Paven, Wichmann, Vollmer, Tremel, Papadopoulos & Butt, Adv. Mater.2015, 27, 7338).
2014 Superamphiphobic particles
We fabricate superamphiphobic particles and find a fundamental limit of how small one can go and still keep superamphiphobicity (Ye, Deng, Ally, Papadopoulos, Schellenberger, Vollmer, Kappl & Butt, Phys. Rev. Lett. 2014, 112, 016101).
2013 Gas exchange membranes and solvent-free synthesis with superamphiphobic layers
Polymeric and composite microspheres can be synthesized without solvents or process liquids by using superamphiphobic surfaces. In this method, the repellency of superamphiphobic layers to monomers and polymer melts and the extremely low adhesion to particles are taken advantage of. Deng, Paven, Papadopoulos, Ye, Wu, Schuster, Klapper, Vollmer & Butt, Angewandte Chemie Intl. Ed. 2013, 52, 11286–11289.
We demonstrate that superamphiphobic gas membranes can be used to exchange CO2 and oxygenate blood. Human blood stored in a superamphiphobic well for 24h can be poured off without leaving cells or adsorbed protein behind. Paven, Papadopoulos, Schöttler, Deng, Mailänder, Vollmer & Butt, Nature Communications 2013, 4, 2512.
2012 Transparent superamphiphobic layers from candle soot
Using candle soot as a template we produce transparent robust superamphiphobic coating. They not only repel water but also oils and surfactant solutions (Deng, Mammen, Butt & Vollmer, Science 2012, 335, 67-70).
2011 Robust, transparent superhydrophobic surfaces
We develop a method to produce transparent, thermally stable and mechanical-ly robust superhydrophobic surfaces made from porous silica capsules (Deng, Mammen, Zhao, Lellig, Müllen, Butt & Vollmer, Adv. Mater. 2011, 23, 2962)
2010 Liquids condense faster on soft surfaces than on hard ones
Sokuler, Auernhammer, Roth, Liu, Bonaccurso, Butt, Langmuir 2010, 26, 1544-1547; Sokuler, Auernhammer, Liu, Bonaccurso, Butt, Europhys. Lett. 2010, 89, 36004.
2009 Nanoadhesion at high separation speeds
Using a modified atomic force microscope we were able to measure adhesion forces at 100 times faster separation velocities. Different regimes of the separation limiting step could be identified on various thiol monolayers (Ptak, Kappl, Moreno-Flores, Gojżewski, Butt, Langmuir 2009, 25, 256-261; Gojzewski, Kappl, Ptak, Butt Langmuir 2010, 26, 1837-1847).
2008 Wet bioadhesion - towards a universal adhesive
The adhesion of a biomimetic DOPA-containing polymer is largely independent on the density of functional groups. This finding should allow designing universal adhesion polymers (Wang et al., Adv. Materials 2008, 20, 3872
2007 Stress and failure at mechanical contacts of microspheres
Measurement of the stress distribution in hard microcontacts. Hertz theory describes the stress distribution adequately. Failure by the formation of nano- and microcracks (Chen, Koynov, Butt, J. Mater. Res. 2007, 22, 3196.
The surface structure on the sub-1 nm scale can explain adhesion forces measured between particles at different humidity (Farshchi, Kappl, Cheng, Gutmann, Butt, Langmuir 2006, 22, 2171). A simple way to take surface roughness into account is described (Butt, Langmuir 2008, 24, 4715).
First measurements of the evaporation of liquid drops with a size much smaller than 100 µm. Therefore microcantilevers were applied (Bonaccurso, Butt, J. Phys. Chem. B 2005, 109, 253; Golovko, Butt, Bonaccurso, Langmuir 2009, 25, 75).
2002 Rupture of molecularly thin films
Theory and experiment on the rupture of lipid bilayers and molecular films in atomic force microscopy (Loi, Sun, Franz, Butt, Phys. Rev. E. 2002, 66, 031601).
2004 Surface forces across polymer melts
Surface forces across polymer melts are dominated by slow processes at the polymer-solid interface (Langmuir 2004, 20, 8030; Macromolecules 2004, 37, 6086; Macromolecules 2007, 40, 2520; J. Phys. Chem. B 2008, 112, 2001).
2000 Liquid-like layer on ice
We studied the properties of ice with the atomic force microscope and measured the thickness of the liquid-like layer on top of the solid ice surface (Döppenschmidt, Butt, Langmuir 2000, 16, 6709).
1999 Adhesion and friction between fine particles
Measuring for the first time the adhesion and rolling friction forces between micron-sized particles (Heim, Blum, Preuss, Butt, Phys. Rev. Lett. 1999, 83, 3328). Latter quantitative measurements of friction acting between individual fine particles were carried out (Ecke, Butt, J. Colloid Interface Sci. 2001, 244, 432).
1996 Microcantilever sensors
Based on earlier work by Thundat (Thundat, Warmack, Chen, Allison, Appl. Phys. Lett. 1994, 64, 2894) and Raiteri, Grattarola, Butt (Raiteri & Butt, J. Phys. Chem. 1995, 99) it was realized that AFM cantilevers can be used to measure changes in the surface tension of solids. This can be applied to build micromechanical sensors (Butt, J. Colloid Interface Sci. 1996, 180, 251). See also Berger (Berger et al., Science 1997, 276, 2021).
Discovery that an organic monolayer can be deposited by the tip of an AFM with sub 100 nm accuracy by scanning force microscopy (Jaschke, Butt, Langmuir 1995, 11, 1061). Mirkin later applied it to deposit thiols on gold. He coined the term "dip-pen lithography" (Piner, Zhu, Xu, Hong, Mirkin, Science 1999, 283, 661).
1994 Particle-bubble interaction
First measurements of single micron-sized particles and air bubbles in water (Butt, J. Colloid Interface Sci. 1994, 166, 109; Preuss, Butt, Langmuir 1998, 14, 3164). Ducker, Xu and Israelachvili did similar experiments in the same year with an atomic force microscope (Ducker, Xu, Israelachvili, Langmuir 1994, 10, 3279) followed by Fielden, Hayes & Ralston (Fielden, Hayes, Ralston, Langmuir 1996, 12, 3721).
1992 Local charge density in aqueous electrolyte with the atomic force microscope
Measuring local charge densities in aqueous electrolyte with sub 100 nm resolution with the AFM (Butt, Biophys. J. 1992, 63, 578).
1991 Colloidal Probe Technique
Demonstration that the atomic force microscope can be used for quantitative force-versus-distance experiments; attaching particles to atomic force microscope cantilevers (Butt, Biophys. J. 1991, 60, 1438). This discovery was independent and in parallel to Ducker, Senden and Pashley (Ducker, Senden, Pashley, Nature 1991, 353, 239). Ducker et al. coined the name “colloidal probe technique”. Meanwhile the AFM has become the standard instrument to measure surface forces.