Figure 5. Swim pressure of Janus particles in different degrees of confinement.

The parameter is a ratio of the particles' run length to the trap size R_c=ζU₀/k. The solid black curves are the theoretical prediction with a harmonic trap approximation, and the red and blue symbols are results from experiments and Brownian dynamics simulations, respectively. A smaller trap size diminishes the distance the particles travel between reorientations and decreases the swim pressure. The experimental and simulation data are averages of 150 and 90 independent particle trajectories for a duration of 40s for the α=0.29 and α=1.76 cases, respectively.