Papers by Stephan Herminghaus
Strukturbildung in dünnen Filmen
Phase separation in driven granular gases: exploring the elusive character of nonequilibrium steady states
Soft Matter
MaxSynBio: Avenues Towards Creating Cells from the Bottom Up
Angewandte Chemie (International ed. in English), Jan 8, 2018
A large German research consortium mainly within the Max Planck Society ("MaxSynBio") w... more A large German research consortium mainly within the Max Planck Society ("MaxSynBio") was formed to investigate living systems from a fundamental perspective. The research program of MaxSynBio relies solely on the bottom-up approach to synthetic biology. MaxSynBio focuses on the detailed analysis and understanding of essential processes of life through modular reconstitution in minimal synthetic systems. The ultimate goal is to construct a basic living unit entirely from non-living components. The fundamental insights gained from the activities in MaxSynBio could eventually be utilized for establishing a new generation of biotechnological processes, which would be based on synthetic cell constructs that replace the natural cells currently used in conventional biotechnology.
The dynamics of the photochromic effect in tungsten trioxide
Solid State Communications
The dynamics of granular matter
AIP Conference Proceedings
We present a numerical study of a shear-induced solid-fluid transition in wet granular matter in ... more We present a numerical study of a shear-induced solid-fluid transition in wet granular matter in order to show the self-organized critical behavior close to the transition point. The continuous time simulation is based on a simple model considering both the cohesive forces induced by the adsorbed liquid amount and the repulsive forces due to the hard core interaction of the
Radar for tracer particles
The Review of scientific instruments, 2017
We introduce a radar system capable of tracking a 5 mm spherical target continuously in three dim... more We introduce a radar system capable of tracking a 5 mm spherical target continuously in three dimensions. The 10 GHz (X-band) radar system has a transmission power of 1 W and operates in the near field of the horn antennae. By comparing the phase shift of the electromagnetic wave traveling through the free space with an IQ-mixer, we obtain the relative movement of the target with respect to the antennae. From the azimuth and inclination angles of the receiving antennae obtained in the calibration, we reconstruct the target trajectory in a three-dimensional Cartesian system. Finally, we test the tracking algorithm with target moving in circular as well as in pendulum motions and discuss the capability of the radar system.
Scientific reports, Jan 27, 2017
Wettability is an important factor which controls the displacement of immiscible fluids in permea... more Wettability is an important factor which controls the displacement of immiscible fluids in permeable media, with far reaching implications for storage of CO2 in deep saline aquifers, fuel cells, oil recovery, and for the remediation of oil contaminated soils. Considering the paradigmatic case of random piles of spherical beads, fluid front morphologies emerging during slow immiscible displacement are investigated in real time by X-ray micro-tomography and quantitatively compared with model predictions. Controlled by the wettability of the bead matrix two distinct displacement patterns are found. A compact front morphology emerges if the invading fluid wets the beads while a fingered morphology is found for non-wetting invading fluids, causing the residual amount of defending fluid to differ by one order of magnitude. The corresponding crossover between these two regimes in terms of the advancing contact angle is governed by an interplay of wettability and pore geometry and can be pr...
Nichts Neues: Zu: „Suprafluides Helium - tröpfchenweise”︁, Phys. Bl., Januar 1998, S. 19
Physik Journal, 1998
Berichte der Bunsengesellschaft für physikalische Chemie, 1994
Experiments were performed on thl: latcral transpoti kinetics of wetting layers. Optically excite... more Experiments were performed on thl: latcral transpoti kinetics of wetting layers. Optically excited s~irface plasinon~ were used to study both the spreading behaviour of silicon oil and the equilibration dynamics of ethanol. The precursor film profiles of silicon oil wcrc found to agree well with the theory of viscous flow of nonvolatile 11quids. For ethanol, evaporation effects and VISCOUS transport could be observcd ~epai-alely. Apparently, the viccous transport is suppressed by almost two orders of magnitude. Possible explanation< are discussed.
Electro-optic polyurea waveguides by in-situ polymerization from the vapor phase
Nonlinear Optical Properties of Organic Materials VI, 1993
ABSTRACT Electro-optically active planar waveguides of aromatic polyurea were prepared by simulta... more ABSTRACT Electro-optically active planar waveguides of aromatic polyurea were prepared by simultaneous deposition of 4,4&#39;-diamino-diphenyl-methane and 4,4&#39;-diphenylmethane- diisocyanate from the vapor phase and subsequent corona poling. Attenuated total reflectance spectroscopy of the waveguide modes of the polymer films was used to measure the piezoelectric and electro-optic susceptibilities. It is found that the electro-optic response is not only determined by the nonlinear polarizability of the urea groups but also from their dipolar orientation in the applied field.
The European physical journal. E, Soft matter, Jun 1, 2016
In this study, we present a PDMS-based microfluidic platform for the fabrication of both liposome... more In this study, we present a PDMS-based microfluidic platform for the fabrication of both liposomes and polymersomes. Based on a double-emulsion template formed in flow-focusing configuration, monodisperse liposomes and polymersomes are produced in a controlled manner after solvent extraction. Both types of vesicles can be formed from the exact same combination of fluids and are stable for at least three months under ambient storage conditions. By tuning the flow rates of the different fluid phases in the flow-focusing microfluidic design, the size of the liposomes and polymersomes can be varied over at least one order of magnitude. This method offers a versatile tool for future studies, e.g., involving the encapsulation of biological agents and the functionalization of artificial cell membranes, and might also be applicable for the controlled fabrication of hybrid vesicles.
The European physical journal. E, Soft matter, Jun 1, 2016
The behaviour of artificial microswimmers consisting of droplets of a mesogenic oil immersed in a... more The behaviour of artificial microswimmers consisting of droplets of a mesogenic oil immersed in an aqueous surfactant solution depends qualitatively on the conditions of dimensional confinement; ranging from only transient aggregates in Hele-Shaw geometries to hexagonally packed, convection-driven clusters when sedimenting in an unconfined reservoir. We study the effects of varying the swimmer velocity, the height of the reservoir, and the buoyancy of the droplet swimmers. Two simple adjustments of the experimental setting lead to a suppression of clustering: either a decrease of the reservoir height below a certain value, or a match of the densities of droplets and surrounding phase, showing that the convection is the key mechanism for the clustering behaviour.
Liquid morphologies and capillary forces between three spherical beads
Physical Review E, 2016
Equilibrium shapes of coalesced pendular bridges in a static assembly of spherical beads are comp... more Equilibrium shapes of coalesced pendular bridges in a static assembly of spherical beads are computed by numerical minimization of the interfacial energy. Our present study focuses on generic bead configurations involving three beads, one of which is in contact to the two others while there is a gap of variable size between the latter. In agreement with previous experimental studies, we find interfacial &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;trimer&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; morphologies consisting of three coalesced pendular bridges, and &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;dimers&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; of two coalesced bridges. In a certain range of the gap opening we observe a bistability between the dimer and trimer morphology during changes of the liquid volume. The magnitude of the corresponding capillary forces in presence of a trimer or dimer depends, besides the gap opening, only on the volume or Laplace pressure of the liquid. For a given Laplace pressure, and for the same gap opening, the capillary forces induced by a trimer are only slightly larger than the corresponding forces in the presence of three pendular bridges. This observation is consistent with a plateau of capillary cohesion in terms of the saturation of a wetting liquid in the funicular regime, as reported in the experimental work [Scheel et al., Nat. Mater. 7, 189 (2008)1476-112210.1038/nmat2117].
Scientific reports, Jan 4, 2016
Experiments and computer simulations are carried out to investigate phase separation in a granula... more Experiments and computer simulations are carried out to investigate phase separation in a granular gas under vibration. The densities of the dilute and the dense phase are found to follow a lever rule and obey an equation of state. Here we show that the Maxwell equal-areas construction predicts the coexisting pressure and binodal densities remarkably well, even though the system is far from thermal equilibrium. This construction can be linked to the minimization of mechanical work associated with density fluctuations without invoking any concept related to equilibrium-like free energies.
Dewetting through nucleation
Comptes Rendus Physique, Nov 1, 2006
ABSTRACT
Time resolved study of excimer laser ablation of thin organic films from a metal surface
Zusammenfassung: The dynamics of pulsed excimer laser ablation of thin films of organic material ... more Zusammenfassung: The dynamics of pulsed excimer laser ablation of thin films of organic material from a metal surface was investigated using optically excited surface plasmons. The metal substrate is formed by a 500 Ǻ thick silver film adjacent to the base of a glass prism, ...
Electroactuation of Fluid Using Topographical Wetting Transitions
Langmuir, 2005
The complex morphologies of liquids on topographically structured substrates are exploited for li... more The complex morphologies of liquids on topographically structured substrates are exploited for liquid actuation in open microchannels. The liquid is either confined in prefabricated grooves, thus forming elongated filaments, or gathers in macroscopic drops without invading the grooves, depending on conditions. Using the electrowetting effect, we can reversibly switch between these two states. The length of the filaments is sensitive to the ionic content of the liquid and can be described quantitatively with an electrical model considering the voltage drop along the groove.
Emulsifying Device and Process for Forming an Emulsion
Microfluidics with Gel Emulsions
Microfluidic processing is usually achieved using single phase liquids. Instead, we use monodispe... more Microfluidic processing is usually achieved using single phase liquids. Instead, we use monodisperse emulsions to compartment liquids within microchannel geometries. At low continuous phase volume fractions, droplets self-organize to form well-defined arrangements, analogous to foam. While it is well-known that confined geometries can induce rearrangement of foam compartments at the millimeter-scale, similar dynamics are also expected for gel emulsions. We
Transport Dynamics in Open Microfluidic Grooves
Langmuir, May 1, 2007
In microscopic rectangular grooves various liquid wetting morphologies can be found, depending on... more In microscopic rectangular grooves various liquid wetting morphologies can be found, depending on the wettability and details of the geometry. When these morphologies are combined with a method to vary the apparent contact angle reversibly, transitions between droplike objects and elongated liquid filaments can be induced. Liquid can thus be transported on demand along the grooves. The dynamics of liquid filaments advancing into grooves as well as receding from grooves has been studied, varying the contact angle using the electrowetting effect. The dynamics of the receding filament is purely capillarity driven and depends only on the contact angle, the viscosity of the liquid, and the geometry of the groove. The length and the dynamics of the advancing filaments, on the other hand, are strongly dependent on the ionic content of the liquid and the applied ac voltage.
Uploads
Papers by Stephan Herminghaus