  This work presents analytical formulas derived for evaluating vapor transport
of a volatile solvent for an isolated multicomponent droplet in a quiescent
environment, based on quasi-steady-state approximation. Among multiple solvent
components, only one component is considered to be much more volatile than the
rest such that other components are assumed to be nonvolatile remaining
unchanged in the droplet during the process of (single-component) volatile
solvent evaporation or condensation. For evaporating droplet, the droplet size
often initially decreases following the familiar "d^2 law" at an accelerated
rate. But toward the end, the rate of droplet size change diminishes due to the
presence of nonvolatile cosolvent. Such an acceleration-deceleration reversal
behavior is unique for evaporating multicomponent droplet, while the droplet of
pure solvent has an accelerated rate of size change all the way through the
end. This reversal behavior is also reflected in the droplet surface
temperature evolution as "S-shaped" curves. However, a closer mathematical
examination of conditions for acceleration-deceleration reversal indicates that
the acceleration phase may disappear when the amount of nonvolatile cosolvent
is relatively small and ambient vapor pressure is relatively high. Because the
net effect of adding nonvolatile cosolvent is to reduce the mole fraction of
the volatile solvent such that the saturation vapor pressure is lowered, vapor
condensation onto the multicomponent droplet is predicted to occur when the
ambient vapor pressure is subsaturated with respect to that for the pure
volatile solvent. In this case, the droplet will grow asymptotically toward a
finite size. But when the ambient vapor pressure becomes supersaturated with
respect to that for the pure volatile solvent, the condensation growth of
droplet can continue indefinitely without bound.
