Droplets Coulomb Fission

Spontaneous Coulomb fission of water droplets on lubricated surfaces describes how electrically charged droplets deform and ultimately break apart when electrostatic forces overcome the stabilizing effect of surface tension. The phenomenon is governed by a subtle balance between charge accumulation, capillary pressure, viscous dissipation, and the interfacial properties of the lubricating layer. Unlike droplets resting on ordinary solid surfaces, droplets on lubricated substrates experience reduced pinning and greater mobility, which can significantly alter the onset and morphology of breakup. These conditions give rise to rich electrohydrodynamic behavior, including shape instabilities, tip formation, charge redistribution, and satellite droplet emission. Studying these dynamics helps clarify how electric fields interact with soft fluid interfaces in low-friction environments. This understanding is relevant to broader problems in fluid transport, surface engineering, and electrically controlled manipulation of liquids. (Lin et al., 2026).

References

2026

Spontaneous Coulomb fissions of drops on lubricated surfaces

Marcus Lin, Peng Zhang, Aaron D Ratschow, Oscar Li, Sankara Arunachalam, and Dan Daniel

Proc. Natl. Acad. Sci. U. S. A., May 2026

Abs

Charged water drops are more widespread than commonly acknowledged. For example, raindrops typically carry charges of order [Formula: see text] pC, while routine pipetting in the laboratory produces drops with [Formula: see text] pC. Here, we show that such modest charging can spontaneously generate periodic Coulomb fissions for evaporating water drops on lubricated surfaces, with more than 60 successive cycles observed over 30 min. Interestingly, the underlying instability can be quantitatively predicted by two fissility thresholds: one marking the onset of drop elongation and another triggering fission. Each fission culminates with a fine liquid jet that disintegrates into 40 to 50 microdroplets, expelled within microseconds. The phenomenon spans an extraordinary range of length scales (from millimeters to microns) and time scales (hours to microseconds), with broad potential applications ranging from nanoscale fabrication to electrospray ionization.