Liquid Marbles as Micro‐bioreactors for Rapid Blood Typing

Due to their unique properties, liquid marbles have been the subject of a collection of studies in the past decade, centered on fundamental research on their properties, as well as their practical applications. [ 1–37 ] These liquid droplets, enwrapped with solid powder while having no direct contact with the supporting substrate, may be exploited for a wide range of applications ranging from, but not limited to, the displacement of a small volume of liquid without any leak left behind, [ 2 ] water surface pollution detection, [ 13 ] gas detection, gas–liquid reactions, [ 8 , 30 , 31 ] and, last but not the least, preparation of microreactors. [ 7 , 30 , 31 , 34 ] With numerous powder types available, the fabrication options of liquid marbles seem to be infinite. This enables the design of tailor-made liquid-marble-based systems for intended applications. To our knowledge, fabrication of microreactors by forming liquid marbles for the purpose of containing chemical reactions at the micrometer scale has been proposed by only a limited number of studies. For instance, Xue et al. [ 34 ] have shown that a liquid marble coated with magnetic powder can be used as a miniature chemical reactor to either encapsulate the reagents in a single marble, or in two separate marbles, which could coalesced afterwards to trigger the reaction. The authors used fluorinated decyl polyhedral oligomeric silsesquioxane and magnetic powder aggregates to generate stable liquid marbles capable of encapsulating liquids of either high or low surface tension. They also demonstrated a chemiluminescence reaction between hydrogen peroxide and bis (2,4,6-trichlorophenyl) oxalate and a dye to prove the concept of the controllable liquid marble microreactors. Tian et al. [ 30 , 31 ] showed that the porous nature of the liquidmarble shell could be used to allow gases to transport through the marble shell. They demonstrated the use of liquid marbles formed with gas-reactive indicator solutions to detect gases. Bormashenko et al. [ 8 ] have also reported the use of polyvinylidene fl uorid particles of micrometer size for fabrication of a liquid marble microreactor containing ammonia acetate, acetic acid, and acetylacetone, which is then exposed to formaldehyde vapor to trigger the reaction.