FIG. 4.

Measured lengths of on-demand generated droplets in devices in two different materials: glass (empty diamonds) and PDMS (solid squares), respectively. The channel widths at the droplet generation junction are identically 70 μm for both devices. The duration of on-demand actuation is set constant at 1 ms for all data points. Four different regimes of operations depending on $\Delta P_{\mathit{n}\mathit{o}\mathit{z}\mathit{z}\mathit{l}\mathit{e}}^{*}$ are denoted with Roman numbers: no droplets (I), premature droplets (II), mature droplets (III), and overmature droplets (IV).