Scientists at the Indian Institute of Science (IISc) have pioneered an innovative technique for encapsulating liquid droplets with wide-ranging applications, from single crystal growth to cell culture. Harnessing the capillary effect – the upward movement of liquid through a narrow space – the method involves coating droplets with a composite shell containing oil-loving and hydrophobic particles. This approach allows for precise tuning of the shell thickness, facilitating the encapsulation of droplets of varying sizes. The study detailing this technique has been published in Nature Communications.
Droplets play pivotal roles in diverse fields such as microreactors, drug delivery systems, crystallization studies, and cell culture platforms. Lead researcher Rutvik Lathia, a Ph.D. student at the Center for Nano Science and Engineering (CeNSE), IISc, underscores the significance of droplets in creating distinct reaction environments, delivering drugs, controlling crystal growth, and fostering controlled cell culture environments.
Despite their utility, droplets present challenges, including susceptibility to contamination, dependence on the surface they are dropped on, and rapid evaporation. While encapsulating droplets with immiscible liquids or solids is a potential solution, creating a robust, continuous shell with adjustable thickness at a minuscule scale has proven elusive.
To overcome these challenges, Prosenjit Sen, Associate Professor at CeNSE, and his team devised a capillary force-assisted cloaking method. They coated droplets with hydrophobic beads, transforming them into “liquid marbles” (LM). Placing these LM on oil-infused surfaces initiated capillary forces, causing the oil to rise into tiny pores between beads. The beads played a crucial role in stabilizing a liquid film around the droplet, effectively encapsulating it. The researchers could also use wax instead of oil to create a solid shell by adjusting the temperature.
This encapsulation significantly reduced droplet evaporation rates, extending their lifetimes by up to 200 times. The team demonstrated the flexibility of adjusting shell thickness, ranging from 5 μm to 200 μm, accommodating droplets with volumes from 14 nL to 200 μL.
Prosenjit Sen emphasizes the method’s versatility for applications in chemistry, biology, and materials science, citing the tunable nature of both solid and liquid shells. The researchers successfully grew single crystals using these coated droplets and applied them to biological applications like 3D cell culture, enhancing success rates in growing yeast cells in the lab.
Sen concludes by highlighting their exploration of new materials for capsules with diverse properties, such as polymer-based capsules, to further enhance tunability in their encapsulation technique.