  We perform a static analysis of a circular cylinder that forms a barrier
between surfactant-laden and surfactant-free portions of a liquid$-$gas
interface. In addition to determining the general implications of the balances
for forces and torques, we quantify how the imbalance
$\Delta\gamma=\gamma_a-\gamma_b$ between the uniform surface tension $\gamma_a$
of the surfactant-free portion of the interface and the uniform surface tension
$\gamma_b$ of the surfactant-laden portion of the interface influences the
load-bearing capacity of a hydrophobic cylinder. Moreover, we demonstrate that
the difference between surface tensions on either side of a cylinder with a
cross-section of arbitrary shape induces a horizontal force component $f^h$
equal to $\Delta \gamma$ in magnitude, when measured per unit length of the
cylinder. With an energetic argument, we show that this relation also applies
to rod-like barriers with cross-sections of variable shape. In addition, we
apply our analysis to amphiphilic Janus cylinders and we discuss practical
implications of our findings for Marangoni propulsion and surface pressure
measurements.
