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Droplets move over viscoelastic substrates by surfing a ridge
S Karpitschka1, S Das2, M van Gorcum1
1Physics of Fluids Group, Faculty of Science and Technology, Mesa+ Institute, University of Twente, 7500 AE Enschede, The Netherlands.
Nature Communications
|August 5, 2015
Summary
Drops on soft solids move by surfing a ridge, deforming the surface into a sharp angle dependent on velocity. This discovery explains stick-slip motion and has implications for cell tissue self-organization and microrheometers.
Area of Science:
- Physics
- Materials Science
- Soft Matter Physics
Background:
- Liquid drops on soft solids cause significant surface deformations due to capillary and elastic forces.
- Drop movement on soft substrates can lead to substantial energy dissipation within the material.
Purpose of the Study:
- To investigate the mechanism of liquid drop movement on soft solids.
- To develop a theoretical model explaining the observed phenomena and predict dynamic behaviors.
- To explore the implications of this phenomenon in biological and engineering applications.
Main Methods:
- Experimental measurement of the contact line angle for water drops on silicone gel.
- Theoretical modeling based on substrate rheology to explain drop dynamics.
- Analysis of the relationship between contact line velocity and surface deformation.
Main Results:
- Drops move by deforming the soft substrate into a sharp 'wetting ridge' whose angle depends on the contact line velocity.
- A quantitative theory was developed that accurately predicts the dynamic contact angle.
- A mechanism for stick-slip motion was identified, involving the contact line depinning and sliding down the wetting ridge.
Conclusions:
- The 'surfing a ridge' mechanism explains liquid drop dynamics on soft solids.
- The developed theory provides a quantitative understanding of dynamic contact angles and stick-slip motion.
- Findings have potential applications in understanding cell tissue self-organization and designing microrheometers.
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