Figure 3. Permeability and slip length of individual CNTs and BNNTs.

(a) Normalized permeability $(k_{\text{NT}}/k_{no-slip}^{ref})$ of CNTs (green symbols) and BNNTs (blue symbols) as a function of R_t. The permeability of the R_t =7 nm BNNT was below the experimental detection limit and is indicated as k_NT = 0 for completeness. Error bars correspond to the experimental errors on F_P. (b) R_t dependence of the experimentally determined slip length inside CNTs (green) and BNNTs (blue). Error bars correspond to the uncertainty in the permeability. Salt concentration is C_s=10^-3 M, except for the 33 nm CNT which was studied at both C_s=10^-3 M and C_s=10^-2 M without a detectable difference. In (a) and (b), the horizontal dashed line indicates the no-slip prediction $(k_{\text{NT}}/k_{no-slip}^{ref})=1$ and the green dashed line is a guide to the eye. The error bars on the radius correspond to the experimental uncertainty in the electric characteristics (see Supplementary Methods 2 and 4). The values of the slip lengths are reported in Supplementary Tables 2 and 3.