Fig. 7: Vertical velocity of single microparticles as function of pressure.

Measured vertical velocity of single microparticles as a function of the pressure together with the expected vertical velocity based on Eq. (1) in the free molecular flow regime for δ = 1.442 and ρp = 1.61 × 103 kg m−3 (green line). The error bar in the pressure is determined by experimental limitations, while the error bar in the vertical velocity is represented by the standard deviation of the mean of the singlet velocity distribution.