  The dissolution of liquid nanodroplets is a crucial step in many applied
processes, such as separation and dispersion in food industry, crystal
formation of pharmaceutical products, concentrating and analysis in medical
diagnosis, and drug delivery in aerosols. In this work, using both experiments
and numerical simulations, we \textit{quantitatively} study the dissolution
dynamics of femtoliter surface droplets in a highly ordered array under a
uniform flow. Our results show that the dissolution of femoliter droplets
strongly depends on their spatial positions relative to the flow direction,
drop-to-drop spacing in the array, and the imposed flow rate. In some
particular case, the droplet at the edge of the array can dissolve about 30%
faster than the ones located near the centre. The dissolution rate of the
droplet increases by 60% as the inter-droplet spacing is increased from 2.5
$\mu$m to 20 $\mu$m. Moreover, the droplets close to the front of flow commence
to shrink earlier than those droplets in the center of the array. The average
dissolution rate is faster for faster flow. As a result, the dissolution time
$T_{i}$ decreases with the Reynolds number Re of the flow as $T_{i}\propto
Re^{-3/4}$. The experimental results are in good agreement with numerical
simulations where the advection-diffusion equation for the concentration field
is solved and the concentration gradient on the surface of the drop is
computed. The findings suggest potential approaches to manipulate nanodroplet
sizes in droplet arrays simply by dissolution controlled by an external flow.
The obtained droplets with varying curvatures may serve as templates for
generating multifocal microlens in one array.
