Fig. 2: Force and perimeter measurements.
From: Direct force measurement of microscopic droplets pulled along soft surfaces
a Side view of a droplet moving with a speed of v = 1 μm s−1. In the image shown, the substrate is moving to the left, so that the droplet motion is towards the right with respect to the substrate. The droplet equilibrium contact angle is ~80∘. The bottom half of the image is the reflection of the droplet and pipette in the substrate (reflection plane indicated within drop). The dashed line is the location where the force is obtained from the micropipette deflection. b The force required to maintain the droplet in a fixed position as the substrate is translated back and forth as a function of time. The force for a set speed, v, is taken from the plateau values indicated in red. c A top-down view of the same droplet at the same moment in time with the axis of symmetry indicated. d Measured perimeter as a function of time obtained from the top view. See Supplementary Movie 1 for sample experiment movie.
