2018/01/29 by Joshua A. Bull, Bull, Joshua A., Alex Hargreaves +6
Engineering · Materials Science · #Characterization and Applications of Magnetic Nanoparticles #FOS: Physical sciences #Innovative Microfluidic and Catalytic Techniques Innovation #Pickering emulsions and particle stabilization #Soft Condensed Matter (cond-mat.soft)
paper · pdf · doi:10.48550/arxiv.1801.09755
openalex publication_date 2018/01/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
When a surfactant-stabilised oil droplet with an ultralow interfacial tension\nis trapped in the focus of two laser beams and pulled apart (by moving the\nlaser beams) a configuration of two droplets connected by a thin tether of oil\nresults. The tether radius depends on the ratio of the bending modulus to the\nrenormalized interfacial tension, which takes into account the spontaneous\ncurvature of the interface. The force exerted by the tether on the droplets is\nshown to be asymmetric with respect to the phase inversion temperature of the\nemulsion, in agreement with experiment. Fluid can be pumped from one droplet to\nthe other via the tether by increasing the optical pressure on one droplet. The\nflow is a combination of Poiseuille flow within the thread of oil and the\nexternal flow around a rigid cylinder, with the surface velocity determined by\ntangential stress balance. For typical viscosities of oils and the continuous\naqueous medium, flow is predominantly in the external medium. The normal stress\nbalance leads to a variation in the radius of the thread with distance. The\nradius is shown to decrease approximately linearly with a slope proportional to\nthe volumetric flow rate through the tether. For a tether of a given length,\nthere is therefore an upper limit to the flow rate that can be generated by\npumping with optical traps.\n