Residence time measurements. (
a– f) Histograms of the residence time probability distribution showing the exponential decay of the residence times of trapped Au NPs in different device geometries (dashed lines are exponential fits) at a concentration of c 0=0.1 mM. ( a– c) 60 nm (dark green, a), 80 nm (dark brown, b), and 100 nm (blue, c) Au NPs trapped in devices with a nanofluidic channel height of h c=210 nm, a pocket depth of h p=70 nm (device geometry G 1) and a width of w p=500 nm, N=278, 281 and 104 trapping events. ( d and e) 60 nm (middle green, d) and 80 nm (light brown, e) Au NPs trapped in G 2/ w p=250 nm, N=290 and 235 trapping events. f) 60 nm Au NPs trapped in G 2/ w p=500 nm, N=275 trapping events. ( g) Kramers time corresponding to the histogram distributions of ( a– f) as a function of particle diameter. ( h) Potential depths Q in k B T as a function of particle diameter calculated from the experimentally obtained Kramers time and from simulations (dashed lines). ( i) Simulation of the electrostatic potential of a point charge of −1 e by solving the nonlinear Poisson-Boltzmann equation numerically for the device geometry G 1 and a pocket width of w p=500 nm. ( j) Extraction of the electrostatic potential difference of a point charge of −1 e for the device geometry G 1/ w p=500 nm, G 2/ w p=250 nm and G 2/ w p=500 nm as a function of r along the axial energy minimum (black dashed line in i).