A research team developed a technique that uses condensation to noninvasively refill liquid marbles with water. The method could improve the viability of applications such as drug delivery. It could also establish improved opportunities for the droplet-size microreactors to see use in opto- and microfluidics.
Liquid marbles are droplets of solution that wrap in a thin layer of microparticles that can be used for a large number of biological, chemical, and biochemical applications. They are used as microreactors to house various chemical, biochemical, and biological purposes like growing cells and applications such as the common PCR [polymerase chain reaction] test, a DNA amplification technique used to detect COVID-19.
The benefit to refilling liquid marbles noninvasively stems from their tendency to collapse due to evaporation. They are created when a droplet of reaction solution is rolled over a powder bed of hydrophobic (water-resistant) or oleophobic (oil-resistant) particles. The marbles create a barrier around the reaction solution that isolates the content from the surroundings.
Once the marbles are formed, however, evaporation can cause them to lose volume, buckle, and, ultimately, to collapse. This eliminates the advantages of their physical properties and their aptitude for use. The particle coating that forms around the droplet can contain liquid which varies in volume from a few nanoliters to a few microliters.