Liquid crystal induced elasto-capillary suppression of crack formation in thin colloidal films

TL;DR

This paper demonstrates that adding a small amount of nematic liquid crystal to colloidal droplets during drying can completely suppress crack formation by absorbing capillary stress, improving coating quality.

Contribution

The study introduces a novel method of crack suppression in drying colloidal films using nematic liquid crystals, highlighting their elastic properties as a stress-absorbing cushion.

Findings

Crack formation is fully suppressed with minimal NLC addition.

NLCs provide a capillary stress-absorbing cushion at the interface.

Potential industrial applications for crack-free coatings are identified.

Abstract

Drying of colloidal droplets on solid, rigid substrates is associated with a capillary pressure developing within the droplet. In due course of time, the capillary pressure builds up due to droplet evaporation resulting in the formation of a colloidal thin film that is prone to crack formation. In this study, we show that introducing a minimal amount of nematic liquid crystal (NLC) can completely suppress the crack formation. The mechanism behind the curbing of the crack formation may be attributed to the capillary stress-absorbing cushion provided by the elastic arrangements of the liquid crystal at the substrate-droplet interface. Cracks and allied surface instabilities are detrimental to the quality of the final product like surface coatings, and therefore, its suppression by an external inert additive is a promising technique that will be of immense importance for several industrial applications. We believe this fundamental investigation of crack suppression will open up an entire avenue of applications for the NLCs in the field of coatings, broadening its already existing wide range of benefits.