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Garcia-Gonzalez D, Hack MA, Kappl M, Butt HJ, Snoeijer JH. Drawing liquid bridges from a thin viscous film. Soft Matter 2023; 19:1241-1248. [PMID: 36688683 DOI: 10.1039/d1sm01750k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
When a particle, such as dust, contacts a thin liquid film covering a surface it is trapped by the liquid. This effect is caused by the formation of a meniscus, resulting in a capillary force that makes the particle adhere to the surface. While capillary adhesion is well-characterised in static situations, the dynamic formation of the liquid bridge after the initial contact is highly intricate. Here, we experimentally study the evolution of a liquid bridge after a glass sphere is gently brought into contact with a thin viscous film. It is found that the contact creates a ripple on the thin film, which influences the growth of the meniscus. Initially, the ripple and the meniscus are coupled and exhibit similar dynamics. This initial regime is well accounted for by a scaling law derived from lubrication theory. At a later stage, the ripple is "detached" from the liquid bridge, leading to a second regime of bridge dynamics. As a result, capillary forces are time-dependent, highlighting the importance of dynamics on adhesion.
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Affiliation(s)
- Diana Garcia-Gonzalez
- Physics of Fluids Group, Max-Planck Center Twente for Complex Fluid Dynamics, Department of Science and Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede, Netherlands.
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Michiel A Hack
- Physics of Fluids Group, Max-Planck Center Twente for Complex Fluid Dynamics, Department of Science and Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede, Netherlands.
| | - Michael Kappl
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Jacco H Snoeijer
- Physics of Fluids Group, Max-Planck Center Twente for Complex Fluid Dynamics, Department of Science and Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede, Netherlands.
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Dekker PJ, Hack MA, Tewes W, Datt C, Bouillant A, Snoeijer JH. When Elasticity Affects Drop Coalescence. Phys Rev Lett 2022; 128:028004. [PMID: 35089754 DOI: 10.1103/physrevlett.128.028004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Accepted: 12/07/2021] [Indexed: 06/14/2023]
Abstract
The breakup and coalescence of drops are elementary topological transitions in interfacial flows. The breakup of a drop changes dramatically when polymers are added to the fluid. With the strong elongation of the polymers during the process, long threads connecting the two droplets appear prior to their eventual pinch-off. Here, we demonstrate how elasticity affects drop coalescence, the complement of the much studied drop pinch-off. We reveal the emergence of an elastic singularity, characterized by a diverging interface curvature at the point of coalescence. Intriguingly, while the polymers dictate the spatial features of coalescence, they hardly affect the temporal evolution of the bridge. These results are explained using a novel viscoelastic similarity analysis and are relevant for drops created in biofluids, coating sprays, and inkjet printing.
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Affiliation(s)
- Pim J Dekker
- Physics of Fluids Group, Mesa+ Institute, University of Twente, 7500 AE Enschede, The Netherlands
| | - Michiel A Hack
- Physics of Fluids Group, Mesa+ Institute, University of Twente, 7500 AE Enschede, The Netherlands
| | - Walter Tewes
- Physics of Fluids Group, Mesa+ Institute, University of Twente, 7500 AE Enschede, The Netherlands
| | - Charu Datt
- Physics of Fluids Group, Mesa+ Institute, University of Twente, 7500 AE Enschede, The Netherlands
| | - Ambre Bouillant
- Physics of Fluids Group, Mesa+ Institute, University of Twente, 7500 AE Enschede, The Netherlands
| | - Jacco H Snoeijer
- Physics of Fluids Group, Mesa+ Institute, University of Twente, 7500 AE Enschede, The Netherlands
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Hack MA, Kwieciński W, Ramírez-Soto O, Segers T, Karpitschka S, Kooij ES, Snoeijer JH. Wetting of Two-Component Drops: Marangoni Contraction Versus Autophobing. Langmuir 2021; 37:3605-3611. [PMID: 33734702 PMCID: PMC8015233 DOI: 10.1021/acs.langmuir.0c03571] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 02/15/2021] [Indexed: 06/12/2023]
Abstract
The wetting properties of multicomponent liquids are crucial to numerous industrial applications. The mechanisms that determine the contact angles for such liquids remain poorly understood, with many intricacies arising due to complex physical phenomena, for example, due to the presence of surfactants. Here, we consider two-component drops that consist of mixtures of vicinal alkanediols and water. These diols behave surfactant-like in water. However, the contact angles of such mixtures on solid substrates are surprisingly large. We experimentally reveal that the contact angle is determined by two separate mechanisms of completely different nature, namely, Marangoni contraction (hydrodynamic) and autophobing (molecular). The competition between these effects can even inhibit Marangoni contraction, highlighting the importance of molecular structures in physico-chemical hydrodynamics.
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Affiliation(s)
- Michiel A. Hack
- Physics
of Fluids Group, Max Planck Center for Complex Fluid Dynamics, Faculty
of Science and Technology, University of
Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Wojciech Kwieciński
- Physics
of Interfaces and Nanomaterials Group, MESA+ Institute for Nanotechnology, University of Twente,
P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Olinka Ramírez-Soto
- Max
Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| | - Tim Segers
- Physics
of Fluids Group, Max Planck Center for Complex Fluid Dynamics, Faculty
of Science and Technology, University of
Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Stefan Karpitschka
- Max
Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| | - E. Stefan Kooij
- Physics
of Interfaces and Nanomaterials Group, MESA+ Institute for Nanotechnology, University of Twente,
P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Jacco H. Snoeijer
- Physics
of Fluids Group, Max Planck Center for Complex Fluid Dynamics, Faculty
of Science and Technology, University of
Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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Hack MA, Tewes W, Xie Q, Datt C, Harth K, Harting J, Snoeijer JH. Self-Similar Liquid Lens Coalescence. Phys Rev Lett 2020; 124:194502. [PMID: 32469577 DOI: 10.1103/physrevlett.124.194502] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 04/28/2020] [Indexed: 06/11/2023]
Abstract
A basic feature of liquid drops is that they can merge upon contact to form a larger drop. In spite of its importance to various applications, drop coalescence on prewetted substrates has received little attention. Here, we experimentally and theoretically reveal the dynamics of drop coalescence on a thick layer of a low viscosity liquid. It is shown that these so-called "liquid lenses" merge by the self-similar vertical growth of a bridge connecting the two lenses. Using a slender analysis, we derive similarity solutions corresponding to the viscous and inertial limits. Excellent agreement is found with the experiments without any adjustable parameters, capturing both the spatial and temporal structures of the flow during coalescence. Finally, we consider the crossover between the two regimes and show that all data of different lens viscosities collapse on a single curve capturing the full range of the coalescence dynamics.
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Affiliation(s)
- Michiel A Hack
- Physics of Fluids Group, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Walter Tewes
- Physics of Fluids Group, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Qingguang Xie
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Charu Datt
- Physics of Fluids Group, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Kirsten Harth
- Physics of Fluids Group, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
- Institute of Physics, Otto von Guericke University, 39106 Magdeburg, Germany
| | - Jens Harting
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich, Fürther Str. 248, 90429 Nuremberg, Germany
| | - Jacco H Snoeijer
- Physics of Fluids Group, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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Abstract
We study the dewetting of liquid films capped by a thin elastomeric layer. When the tension in the elastomer is isotropic, circular holes grow at a rate which decreases with increasing tension. The morphology of holes and rim stability can be controlled by changing the boundary conditions and tension in the capping film. When the capping film is prepared with a biaxial tension, holes form with a non-circular shape elongated along the high tension axis. With suitable choice of elastic boundary conditions, samples can even be designed such that square holes appear.
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Affiliation(s)
- Rafael D Schulman
- Department of Physics and Astronomy, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1, Canada.
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Berninger B, Hack MA, Götz M. Neural stem cells: on where they hide, in which disguise, and how we may lure them out. Handb Exp Pharmacol 2006:319-60. [PMID: 16370334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
In contrast to the haematopoietic system in which each cell type is subject to constant turnover, thus endowing this system with the permanent ability to reconstitute itself, the nervous system has long been known as an organ devoid of spontaneous cellular reconstitution. Yet the discovery that certain regions of the mammalian central nervous system do sustain neurogenesis throughout life, together with the fact that cells can be isolated from the adult brain that generate neurons in vitro, has led to the idea that the nervous tissue harbours neural stem cells. The term "neural stem cell" has now become associated with enormous expectations for curing diseases of the nervous system. Yet many of the biological fundamentals of neural stem cells need to be revealed before these expectations can be properly judged or even fulfilled. This begins with the question of whether the neural stem cell corresponds to a real entity or rather represents an in vitro dedifferentiation phenomenon. In this chapter we attempt to give an overview of our current knowledge of the biology of the presumable adult neural stem cell. This is followed by a comparative assessment of the possibilities of using adult neural stem cells and embryonic stem cells for therapeutic approaches in the context of neurodegenerative diseases. Finally, we will look at the "evil side" of stemness by discussing the evidence that brain cancers may originate from cells with stem cell-like properties.
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Affiliation(s)
- B Berninger
- Institute of Stem Cell Research, GSF-National Research Center for Environment and Health, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany.
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Hack MA, Sugimori M, Lundberg C, Nakafuku M, Götz M. Regionalization and fate specification in neurospheres: the role of Olig2 and Pax6. Mol Cell Neurosci 2004; 25:664-78. [PMID: 15080895 DOI: 10.1016/j.mcn.2003.12.012] [Citation(s) in RCA: 226] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2003] [Revised: 11/19/2003] [Accepted: 12/08/2003] [Indexed: 01/19/2023] Open
Abstract
Neurosphere cultures are widely used to propagate multipotent CNS precursors, but their differentiation into neurons or oligodendrocytes is rather poor. To elucidate fate determination in this system, we examined the expression and function of candidate transcription factors in neurospheres derived from different CNS regions during development and adulthood. We observed prominent down-regulation of most transcription factors present in telencephalic precursors upon growth factor exposure in neurosphere cultures while Olig1 and Olig2 expression was strongly up-regulated. Interference with Olig2 in neurospheres revealed its role in self-renewal during expansion and for the generation of neurons and oligodendrocytes during differentiation. We further show that neurogenesis becomes fully Pax6-dependent in the neurosphere culture system, independent of the region of origin, and that Pax6 overexpression is sufficient to direct almost all neurosphere-derived cells towards neurogenesis. Thus, a pathway combining transcription factors of dorsal and ventral regions is activated in the neurosphere culture model.
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Affiliation(s)
- M A Hack
- Neuronal Specification, Max-Planck-Institute of Neurobiology, D-82152 Martinsried, Germany
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Hack MA, Choi SJ, Vijayapalan P, Davies RJ, Stradling JR. Comparison of the effects of sleep deprivation, alcohol and obstructive sleep apnoea (OSA) on simulated steering performance. Respir Med 2001; 95:594-601. [PMID: 11453317 DOI: 10.1053/rmed.2001.1109] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Patients with obstructive sleep apnoea (OSA) are reported to have an increased risk of road traffic accidents. This study examines the nature of the impairment during simulated steering in patients with OSA, compared to normal subjects following either sleep deprivation or alcohol ingestion. Twenty-six patients with OSA and 12 normal subjects, either deprived of one night's sleep or following alcohol ingestion [mean (SD) alcohol blood level 71.6 mg dl(-1) (19.6)], performed a simulated steering task for a total of 90 min. Performance was measured using the tendency to wander (SD), deterioration across the task, number of 'off-road' events and the reaction time to peripheral events. Control data for OSA, sleep deprivation and alcohol were obtained following treatment with nasal continuous positive airway pressure (nCPAP), after a normal night of sleep, and following no alcohol, respectively. Patients with untreated OSA, and sleep-deprived or alcohol-intoxicated normal subjects performed significantly less well, compared to their respective controls (P<0.01 for all tests), with untreated OSA lying between that of alcohol intoxication and sleep deprivation. Alcohol impaired steering error equally throughout the whole drive, whilst sleep deprivation caused progressive deterioration through the drive, but not initially. Untreated OSA was more like sleep deprivation than alcohol, although there was a wide spread of data. This suggests that the driving impairment in patients with OSA is more compatible with sleep deprivation or fragmentation as the cause, rather than abnormal cognitive or motor skills.
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Affiliation(s)
- M A Hack
- Oxford Centre for Respiratory Medicine, Oxford Radcliffe Trust, UK
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Juniper M, Hack MA, George CF, Davies RJ, Stradling JR. Steering simulation performance in patients with obstructive sleep apnoea and matched control subjects. Eur Respir J 2000; 15:590-5. [PMID: 10759458 DOI: 10.1034/j.1399-3003.2000.15.27.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Patients with obstructive pulmonary disease (OSA) have an increased rate of driving accidents, perhaps due to poor vigilance or impaired cognitive skills that influence their driving ability. The authors have assessed whether patients with OSA perform differently to control subjects on a steering simulator which allows the separate assessment of the two visual tasks required for steering a car, immediate positioning on road with reference to the road edges, and assessment of the curve of the oncoming road which allows faster driving. Twelve patients with OSA and 12 control subjects, matched for age, sex and driving experience, performed three 30-min drives with either all the oncoming road visible, only the near part of the road visible, or only the distant part of the road visible. Steering was assessed by measuring the SD around the theoretical perfect path (steering error) and the number of times the driver went "off road". Subjects identified the appearance of target numbers at the four corners of the screen as quickly as possible, thus making the test a divided attention task. Patients with OSA performed significantly less well on the three different road fields as measured by steering error (p<0.001), time to detect the target number (p<0.03), and off road events (p<0.03). The patients appeared to be particularly impaired on the two drives when only part of the road ahead was available to guide steering. This steering simulator, with its more realistic view of the road ahead, identifies impaired performance in patients with obstructive sleep apnoea. In addition it suggests that patients with obstructive sleep apnoea may be more disadvantaged compared to normal subjects when the view of the road ahead is limited (such as in fog).
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Affiliation(s)
- M Juniper
- Osler Chest Unit, Churchill Hospital, Oxford, UK
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