Elastocapillary Deformation of Nanochannels

Let us first have a look at capillary forces in terms of scaling laws. If the characteristic size of a structure is L, capillary forces are proportional to L, while pressure forces (such as wind drag) or elastic forces are proportional to and body forces (such as gravity) to L. When all the dimensions of a given structure are scaled down, capillary forces decrease slower than pressure and body forces and eventually become dominant. As a consequence. 

Lee sets the typical curvature that capillary forces can induce on a flexible sheet a structure is significantly deformed by surface tension if its length is lai e in comparison with Lee. Indeed capillary forces produce a larger torque (larger lever arm) on a larger structure. If a given structure is scaled down homothetically by a factor A, 1, Lee is multiplied by a factor (Lee and thus 

The meaning of the elastocapillary length is well illustrated by the beautiful experiment performed recently by Py etal They used the interaction between elasticity and capillarity to produce three-dimensional [3D) structures. A liquid droplet is deposited on a thin planar sheet, and when the droplet evaporates it is spontaneously wrapped by the membrane. The final encapsulated 3D shape can be controlled by tailoring the initial geometry of the flat membrane. We now see that the critical length below which encapsulation cannot occur is the elastocapillary length Lee- 

2 Elastocapillahty in nanocapillaries the formation of a liquid meniscus in a flexible fluid channel 

As we saw in Fig. 11.4, thin flexible membranes of micrometersized capillaries can be significantly deformed due to the surface tension forces of the liquid inside. The figure shows silicon oxide channels of several micrometer width and about 80 nm height. These channels are capped by a thin, flexible silicon oxide-silicon 

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