| 1. |
- Style, Robert W., et al.
(author)
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Patterning droplets with durotaxis
- 2013
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 110:31, s. 12541-12544
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Journal article (peer-reviewed)abstract
- Numerous cell types have shown a remarkable ability to detect and move along gradients in stiffness of an underlying substrate-a process known as durotaxis. The mechanisms underlying durotaxis are still unresolved, but generally believed to involve active sensing and locomotion. Here, we show that simple liquid droplets also undergo durotaxis. By modulating substrate stiffness, we obtain fine control of droplet position on soft, flat substrates. Unlike other control mechanisms, droplet durotaxis works without imposing chemical, thermal, electrical, or topographical gradients. We show that droplet durotaxis can be used to create large-scale droplet patterns and is potentially useful for many applications, such as microfluidics, thermal control, and microfabrication.
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| 2. |
- Style, Robert W., et al.
(author)
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Universal Deformation of Soft Substrates Near a Contact Line and the Direct Measurement of Solid Surface Stresses
- 2013
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 110:6, s. 066103-
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Journal article (peer-reviewed)abstract
- Droplets deform soft substrates near their contact lines. Using confocal microscopy, we measure the deformation of silicone gel substrates due to glycerol and fluorinated-oil droplets for a range of droplet radii and substrate thicknesses. For all droplets, the substrate deformation takes a universal shape close to the contact line that depends on liquid composition, but is independent of droplet size and substrate thickness. This shape is determined by a balance of interfacial tensions at the contact line and provides a novel method for direct determination of the surface stresses of soft substrates. Moreover, we measure the change in contact angle with droplet radius and show that Young's law fails for small droplets when their radii approach an elastocapillary length scale. For larger droplets the macroscopic contact angle is constant, consistent with Young's law. DOI: 10.1103/PhysRevLett.110.066103
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