Exploring the Mechanism of Microdroplet Explosion on an Electrified Interface

The importance of microdroplets has become a forefront of science: from catalysis to biologically relevant reactions. Many techniques are used to study these droplets, and even more use them in their workflow: of notable importance is electrospray coupled with mass spectrometry and droplet-based microfluidics. Particularly, electrochemiluminescence (ECL) microscopy of microdroplets has recently elucidated physicochemical phenomena such as interfacial tension and buoyancy forces of microdroplets adsorbed to the surface of an electrode. Here, we use a common ECL system to observe the explosion of an organic microdroplet on the surface of an indium tin oxide (ITO) electrode when a reducing potential is applied. Moreover, we propose a model in which these events are caused by an increase in coulombic repulsion forces from the reduction of benzoyl peroxide, combined with the <i>in operando</i> surface reduction and modification of the electrode. We show that one can modulate the wetting and increase the time to explosion by over 100×, or halt the process by using surfactants and interfacial chemistry. Furthermore, by using the metal oxide electrode, a 1000x less voltage is needed compared to that of traditional electrospray techniques. These results could have broad implications for fields that have been expanded by electrospray, such as geology, materials science, synthesis, and biology.