Evaporation effects in elastocapillary aggregation

Abstract

We consider the effect of evaporation on the aggregation of a number of elastic objects due to a liquid's surface tension. In particular, we consider an array of spring-block elements in which the gaps between blocks are filled by thin liquid films that evaporate during the course of an experiment. Using lubrication theory to account for the fluid flow within the gaps, we study the dynamics of aggregation. We find that a non-zero evaporation rate causes the elements to aggregate more quickly and, indeed, to contact within finite time. However, we also show that the number of elements within each cluster decreases as the evaporation rate increases. We explain these results quantitatively by comparison with the corresponding two-body problem and discuss their relevance for controlling pattern formation in elastocapillary systems.

Elastocapillarity: When Surface Tension Deforms Elastic Solids

“…Successive associations can later on lead to bundles of size 3, 4, 5... and finally to any size below Nmax. Di↵erent approaches have been proposed to describe this distribution from crude mean field (Boudaoud et al, 2007) to more sophisticated dynamical models, such as arrays of rigid plates with elastic hinges (Bernardino andDietrich, 2012, Wei andMahadevan, 2014) or idealised brushes of parallel lamellae (Singh et al, 2014, Hadjittofis et al, 2016. The comparison of the two last references with experimental data is particularly convincing.…”

On thin evaporating drops: When is the -law valid?

“…Machrafi et al 2013;Hadjittofis et al 2015). The equilibrium vapour concentration c e is evaluated using the saturation vapour pressure and we assume that c ∞ = 0 for each of the liquids in the table (since the concentration of these liquid vapours in the atmosphere is negligible).…”

Onset of Elasto-capillary Bundling of Micropillar Arrays: A Direct Visualization

“…However, if the drop wets the array of micrometric pillars (Wenzel state), the pillars in the array may bend and collapse upon draining or evaporation of the liquid. 4 − 7 The response of the pillars depends on their height and material as well as the surface tension of the drop. 8 , 9 …”

“… 11 , 13 There have also been many studies regarding the agglomeration of multiple high-aspect ratio structures like the case of multiple lamellae forced to pierce a liquid’s interface 26 and numerical studies where they used multiple spring block elements to model the cluster size and dynamics on a two-dimensional system. 7 , 27 To our knowledge, however, time-resolved images of the menisci in micropillar arrays during the entire process of bundling, have remained elusive.…”