Engineering Interfacial Processes at Mini-Micro-Nano Scales Using Sessile Droplet Architecture

Abstract

Evaporating sessile functional droplets act as the fundamental building block that controls the cumulative outcome of many industrial and biological applications such as surface patterning, 3D printing, photonic crystals, and DNA sequencing, to name a few. Additionally, a drying single sessile droplet forms a high-throughput processing technique using low material volume which is especially suitable for medical diagnosis. A sessile droplet also provides an elementary platform to study and analyze fundamental interfacial processes at various length scales ranging from macroscopically observable wetting and evaporation to microfluidic transport to interparticle forces operating at a nanometric length scale. As an example, to ascertain the quality of 3D printing we must understand the fundamental interfacial processes at the droplet scale. In this article, we review the coupled physics of evaporation flow-contact-line-driven particle transport in sessile colloidal droplets and provide methodologies to control the same. Through natural alterations in droplet vaporization, one can change the evaporative pattern and contact line dynamics leading to internal flow which will modulate the final particle assembly in a nontrivial fashion. We further show that control over particle transport can also be exerted by external stimuli which can be thermal, mechanical oscillations, vapor confinement (walled or a fellow droplet), or chemical (surfactant-induced) in nature. For example, significant augmentation of an otherwise evaporation-driven particle transport in sessile droplets can be brought about simply through controlled interfacial oscillations. The ability to control the final morphologies by manipulating the governing interfacial mechanisms in the precursor stages of droplet drying makes it perfectly suitable for fabrication-, mixing-, and diagnostic-based applications.

Bismuthene nanosheets produced by ionic liquid assisted grinding exfoliation and their use for oxygen reduction reaction

“…Previous work 17 has indeed demonstrated that the convective evaporation-induced assembly process can be strongly inuenced by convective uid particle transport, including the Marangoni ow, which arises from temperature and concentration gradients. [17][18][19][20] The self-assembled spherules organisation of bismuth nanosheets has not been reported before and demands further in-depth analysis. Importantly, the spheruleslike superstructure with porous morphology could provide highly accessible surfaces, which would be benecial for high ion transport essential for energy storage devices.…”

Transient Prediction of Nanoparticle-Laden Droplet Drying Patterns through Dynamic Mode Decomposition

“…Sessile droplet evaporation studies are normally the smallest laboratories for the understanding of evaporation dynamics, and they can provide wide information contents for real applications in areas such as energy engineering, chemical engineering and chemistry, physics and physical chemistry, biology, biochemistry, medicine, pharmacology, and agricultural and environmental sciences . The sessile colloidal droplets can be investigated for complex drying patterns, , wetting and spreading, , flow instabilities, , and the impact of external forces on evaporation. , The vast majority of droplet evaporation studies are based on single droplet deposition onto the target substrate. The deposited droplet is normally desired to have a spherical caplike shape, which can be modeled via wettability (e.g., contact angle) and droplet height, for better mathematical modeling approaches .…”

“…1 The sessile colloidal droplets can be investigated for complex drying patterns, 2,3 wetting and spreading, 4,5 flow instabilities, 6,7 and the impact of external forces on evaporation. 8,9 The vast majority of droplet evaporation studies are based on single droplet deposition onto the target substrate. The deposited droplet is normally desired to have a spherical caplike shape, which can be modeled via wettability (e.g., contact angle) and droplet height, for better mathematical modeling approaches.…”

Moses Effect: Splitting a Sessile Droplet Using a Vapor-Mediated Marangoni Effect Leading to Designer Surface Patterns

“…Recently, Hegde et al demonstrably increased the natural scale of convection in evaporating droplets by a factor of ∼1000 using vapor-mediated interactions between water and ethanol. Evaporating droplets display a wide range of internal motions driven by interfacial/bulk perturbations. , This motion can segregate dispersed/dissolved matter (molecules, particles, polymers, vesicles, cells, and microorganisms) into a striking array of geometrical structures such as rings, mounds, fingers, and concentric circles, to name a few. Brutin et al have also demonstrated the use of pattern recognition techniques to identify and diagnose afflictions of human blood.…”