Patent ID: 9581535
Date: 2017-02-28
CPC Classifications: G01N

Claim:
1. A method of determining interfacial tension between first and second immiscible liquids, comprising directing a flow of the first liquid surrounded by a flow of the second liquid into a succession of three channels comprising an entrance channel, a cavity and exit channel , where the cavity connects the entrance and exit channels and has a wider cross-section for flow than both the entrance and exit channels, wherein the first liquid enters the cavity as a jet and breaks into droplets within the cavity, and wherein passage of a droplet through the exit channel creates a perturbation which feeds back to perturb the jet entering the cavity, whereby droplets can be formed within the cavity at a stable resonant frequency; supplying an alternating signal to perturb the incoming jet of the first liquid at the frequency of the supplied alternating signal; and varying the frequency of the supplied alternating signal over a range which includes the resonant frequency; observing the frequency of droplet formation while varying the frequency of the supplied alternating signal, so as to determine a frequency bandwidth which extends to either side of the resonant frequency and within which formation of droplets takes place at the frequency of the supplied alternating signal; also directing the flows of first and second liquids through the channels without the said alternating signal so as to determine the resonant frequency of droplet formation without the alternating signal; and determining a ratio of the resonant frequency to the bandwidth as a measurement of interfacial tension between the first and second liquids.