Control of the Drying Patterns for Complex Colloidal Solutions and Their Applications

Abstract

The uneven deposition at the edges of an evaporating droplet, termed the coffee-ring effect, has been extensively studied during the past few decades to better understand the underlying cause, namely the flow dynamics, and the subsequent patterns formed after drying. The non-uniform evaporation rate across the colloidal droplet hampers the formation of a uniform and homogeneous film in printed electronics, rechargeable batteries, etc., and often causes device failures. This review aims to highlight the diverse range of techniques used to alleviate the coffee-ring effect, from classic methods such as adding chemical additives, applying external sources, and manipulating geometrical configurations to recently developed advancements, specifically using bubbles, humidity, confined systems, etc., which do not involve modification of surface, particle or liquid properties. Each of these methodologies mitigates the edge deposition via multi-body interactions, for example, particle–liquid, particle-particle, particle–solid interfaces and particle–flow interactions. The mechanisms behind each of these approaches help to find methods to inhibit the non-uniform film formation, and the corresponding applications have been discussed together with a critical comparison in detail. This review could pave the way for developing inks and processes to apply in functional coatings and printed electronic devices with improved efficiency and device yield.

Tracking colloidal silica particles to evaluate their dispersion and interactions in concentrated suspensions under shear force applications

“…As many processes dealing with colloidal particle suspensions are performed under dynamic environment [24,25], observation under such an environment should be useful. The combination of a confocal/optical microscope and rheometer is a good option to study concentrated colloidal systems under shear application [26,27].…”

Geometrically-controlled evaporation-driven deposition of conductive carbon nanotube patterns on inclined surfaces

“…3 In this regard, evaporationdriven self-assembly has become an effective method for the controllable patterning of nanoparticles. 4 The pinned contact line of an evaporating sessile droplet induces a capillary flow, which causes liquid from the interior part of the droplet to replenish the escaped mass along the three-phase contact line, 5,6 and the higher evaporation rate near the contact line can also enhance this compensatory flow. 7,8 The evaporation-induced flow inside colloidal droplets can deposit CNTs and align them along the contact line.…”

Two-Level Optical Birefringence Created by Evaporation-Induced Polymer Crystallization in Sessile Droplets

“…Evaporation of the volatile solvent usually leads to various deposited patterns. Unveiling the formation mechanism is very challenging because the solvent evaporation is a nonequilibrium dynamic process and is usually associated with complex internal flows. − Past experiments have made great effort in colloids, ,− liquid crystals, , and various suspensions. ,− For example, Deegan , revealed that the capillary flow can transport solutes from the center of a droplet to the evaporating edge, which creates the well-known “coffee rings”. Shao et al showed that the Marangoni flow can align the rod-like cellulose nanocrystals at liquid–air–substrate contact line, leading to concentric deposited pattern with Maltese cross.…”