Comparisons of liquid and gaseous microdrops deposited on surfaces via a retreating tip.

The rupture of a liquid bridge has many applications while the rupture of a gaseous bridge is gaining importance in the use of bubbles to affect the speed of liquid flow over surfaces. Here, comparative experiments were conducted for liquid and gaseous bridges dispensed at fixed volumes of 6 μL on silicone (hydrophobic) and silane coated glass (hydrophilic) surfaces and with the dispensing tip retracted at different speeds. With the liquid bridge, increasing the retracting speed left behind lower volumes on the substrate.