Transition from Stripe-like Patterns to a Particulate Film Using Driven Evaporating Menisci

Abstract

Better control of colloidal assembly by convective deposition is particularly helpful in particle templating. However, knowledge of the different factors that can alter colloidal patterning mechanisms is still insufficient. Deposit morphology is strongly ruled by contact line dynamics, but the wettability properties of the substrate can alter it drastically. In this work, we experimentally examined the roles of substrate contact angle hysteresis and receding contact angle using driven evaporating menisci similar to the dip-coating technique but at a low capillary number. We used smooth substrates with very different wettability properties and nanoparticles of different sizes. For fixed withdrawal velocity, evaporation conditions, and nanoparticle concentration, we analyzed the morphology of the deposits formed on each substrate. A gradual transition from stripe-like patterns to a film was observed as the contact angle hysteresis and receding contact angle were lowered.

Large‐Area Assembly of Densely Aligned Single‐Walled Carbon Nanotubes Using Solution Shearing and Their Application to Field‐Effect Transistors

“…As the solution is sheared over the wafer, the solution contact line (air/liquid/solid interface) is pinned on the solvent‐wetting regions, while less/no pinning occurs on the solvent‐dewetting regions. Previous literature has shown that contact line pinning is important for forming well‐packed particles . When the contact line is pinned, the evaporation rate is accelerated at the contact line, which causes edgeward convective flow and transport of both solvent and SWCNTs towards the contact line .…”

Dynamically controlled deposition of colloidal nanoparticle suspension in evaporating drops using laser radiation

“…17,18 To overcome this effect, several techniques have been proposed by manipulating capillary flows, changing the particle shape and modifying the surface wettability of the substrate. 11,[19][20][21][22][23][24][25] However, the ability to dynamically control the distribution of the suspended particles during evaporation of droplets has rarely been studied.…”

Deposition of Quantum Dots in a Capillary Tube

“…On the other hand, evaporative self-assembly is a promising method in which the nanoparticles can be assembled into a variety of patterns by manipulating parameters such as the evaporation rate, Marangoni effects, etc. For instance, on a planar surface, the self-assembly of micrometer size band structures have been observed in the literature. − Such patterns are believed to originate from the pinning of the contact line of a droplet during the evaporation process, which causes the accumulation of the particles near the contact line in a so-called coffee ring effect. , As the suspension evaporates, the contact line depins before it is pinned again at the next position, and in this sequential way, stripes or multiple irregular rings are formed …”