Bouncing under AC electric field and Coulombic attraction suggest charge transfer between biopolymer microcapsules
Phys. Rev. Fluids 11, 073701 – Published 13 July, 2026
DOI: https://doi.org/10.1103/tf2x-ktb1
Abstract
We report a striking bouncing phenomenon exhibited by pairs of biopolymer microcapsules subjected to a low-frequency AC electric field. The bouncing occurs at twice the applied frequency, suggesting that its origin lies in polarization-induced charge transfer during capsule-capsule contact. This interpretation is supported by the observation that, once the field is removed, the capsules spontaneously attract each other with a force consistent with Coulombic interaction between oppositely charged objects. A minimal toy model incorporating electrophoretic driving and Coulombic attraction captures semiquantitatively the observed dynamics. These findings provide direct experimental evidence of charge transfer in microcapsule suspensions and offer insights into the anomalous gel-like properties of these non-Brownian systems at low volume fractions.
