Chemical processes that occur in small volume containers have many benefits that have only recently become apparent. Containers such as thin films, compartments within microfluidic systems, and droplets require small amounts of solvent and therefore provide an inherently green alternative to reactions that take place in typical laboratory containers. Additionally, reactions that take place in small volumes seem to improve the rates of processes ranging from simple syntheses to protein folding. This increase in rate is attributed to increased surface area availability, rapid reagent mixing times, and increased heat transport properties as compared to the bulk. Acoustic levitation is a popular technique for the suspension of small volumes, most commonly droplets, in a “contact-free” container that preserves the large droplet surface area, a leading contributor to increased chemical activity.

In our laboratory we are coupling acoustic levitation and droplet chemistry with ionic liquids which are rapidly becoming the solvent of choice for many systems. This increased popularity is primarily due to their unique “tunability” and their low vapor pressures. Thus far we have reproducibly levitated 10μL droplets of deionized water, aqueous calcium hydroxide, toluene, and most interestingly the ionic liquid 1-butyl-1methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP-BTI) using an acoustic levitation device reported in the literature as a “TinyLev.” We have currently measured droplet lifetimes for aqueous solutions near 30 minutes, 15 minutes for toluene, and approximately 2 weeks for BMP-BTI. These preliminary results suggest that ionic liquids may be suitable acoustically-levitated droplets and we are currently working to develop a technique for probing the interactions and structure of solutes within an ionic liquid solvent via laser light scattering.