Fig. 8: Oscillating droplet tribometer and centrifugal adhesion balance.

a Schematic of the oscillating droplet tribometer. b Snapshots of the magnetic droplet oscillating around the magnet axis (x = 0 mm). The droplet trajectory is shown in red. Reprinted with permission from ref. ¹¹⁸. c Droplet position x as a function of time t on two different spots on the same superhydrophobic surface. The difference in the oscillation damping rates indicates variation in surface wetting properties. Reprinted with permission from ref. ⁴⁶. d Schematic of the centrifugal adhesion balance, which can be used to measure (e) the adhesion force F_adh and the friction force F_fric. Reprinted with permission from ref. ⁴⁸. f F_fric increases with the resting time of the droplet t_rest up to a plateau value F_fric,∞. Reprinted with permission from ref. ⁴⁷.