This implies that the surface tension is not strong enough to accommodate the increase in the pillar elasticity (Tresco 350).
The elastic modulus of the pillars can also be altered by adding a softener to the original polymer so as to decrease the stiffness of the pillars or mixing the polymers with Si nanoparticles to increase stiffness of the pillars. The result that the number of posts per assembly is inversely proportional to the modulus. When either the diameter or the modulus increases, the observed range of assembly size decreases, showing that the range is proportional to the maximum assembly size (Decker 620).
Figures a, b and c above shows the effect of the pillar modulus concerning the size and arrangement of accumulated clusters. Figure d shows the plot of the number of posts per assembly as a function of the modulus for a certain given diameter (Kang et al. 6325).
Evaporation-induced self-assembly in the micro brushes is due to the competition that exists between the capillary and the Van Der Waals forces. The inter pillar adhesion is also important in determining the nature of the final assembly of the micro bristles. The assembly is normally biphasic. The second phase is very much observable when the pillar stiffness is relatively high as observed in SEM image S2G. A large assembly forms under the influence of the capillary force but as the liquid dries, it breaks into smaller clusters that are equal to the immediate precursors. Given the fact that adhesion alone balances the elastic deformation in the dry system, it is observable that adhesion is not sufficient to maintain the last storage of the assembly. The balance between the adhesion and the elasticity determines the number of hierarchical stages that will be preserved in the micro bristles in the micro brushes. The balance between the elasticity and the capillary will determine the maximum size that the micro