Materials science

Droplets move to softer substrates

Journal name:
Nature
Volume:
498,
Page:
411
Date published:
DOI:
doi:10.1038/498411b
Published online

Liquid droplets dripped onto a silicone gel will move from thin, stiff regions to thick, springy ones.

This intriguing behaviour, reported by Eric Dufresne at Yale University in New Haven, Connecticut, and his colleagues, occurs because of the physics of surface tension. A droplet tends to spread out over a thick, deformable surface, but rears up into a spherical shape at thinner, stiffer places. A similar phenomenon occurs in biology, but in reverse: cells tend to move to stiffer parts of a substrate, a process called durotaxis. The biological movement is thought to involve the cell actively sensing its environment and using actin–myosin fibres to control locomotion. The liquid durotaxis can be used to generate patterns of droplets (pictured) without chemical or thermal gradients and might be useful in microfluidics, the authors speculate.

ROBERT STYLE

Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1307122110 (2013)

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