Liquid Marble Coalescence and Triggered Microreaction Driven by Acoustic Levitation

Liquid
marbles show promising potential for application in the microreactor
field. Control of the coalescence between two or among multiple liquid
marbles is critical; however, the successful merging of two isolated
marbles is difficult because of their mechanically robust particle
shells. In this work, the coalescence of multiple liquid marbles was
achieved via acoustic levitation. The dynamic behaviors of the liquid
marbles were monitored by a high-speed camera. Driven by the sound
field, the liquid marbles moved toward each other, collided, and eventually
coalesced into a larger single marble. The underlying mechanisms of
this process were probed via sound field simulation and acoustic radiation
pressure calculation. The results indicated that the pressure gradient
on the liquid marble surface favors the formation of a liquid bridge
between the liquid marbles, resulting in their coalescence. A preliminary
indicator reaction was induced by the coalescence of dual liquid marbles,
which suggests that expected chemical reactions can be successfully
triggered with multiple reagents contained in isolated liquid marbles
via acoustic levitation.