Figure 5.

Microscope images of an air-water surface inside a tapered micropipette. (a) The air-filled micropipette was inserted into the surfactant solution under relatively high positive applied pipette pressure 18.8 kPa. The meniscus came to equilibrium such that the interface meniscus (diameter ~15 µm) was close to pipette tip. (b–d) The applied positive pressure was then decreased to, (b) 12 kPa, (c) 8.8 kPa, and (d) 7.1 kPa respectively allowing the meniscus to recede down the tapered pipette to new equilibrium curvatures. In the experiment this is followed by a series of increasing pressures that move the meniscus back down the pipette and so is advancing. There was no hysteresis in the positions or contact angle for these receding or advancing contact angles. With permission from American Chemical Society [9].