Capillary attraction: Like-charged particles at liquid interfaces
This is a short but interesting article. In this article, the authors examined the attraction at an oil-water interface between like charged particles. They also confirmed that the particles do have a measurable charge, even when immersed in oil. Through doing experiment, the authors's finding shows that interface distortion due to diploar electric field can induce long range capillary attractions, and such phenomenon is not a result of fundamental force balance. Moreover, the authors states that the range of the capillary distortion is short. In the absence of solubilized charges which results in larger screening length than particle separation, the force imbalance between the particle and the interface will persist far enough for significant interfacial distortion to exist at scales comparable to the interparticle separation. As a result, the authors believe that electric-field-induced capillary distortion is the most likely cause for the attractive interactions between like-charged interfacial particles.