Transport and Self-Breakup of Drops for On-Chip Microfluidics

We report a microfluidic transport technique which divides a given small volume of liquid into equal portions with no external input after the drop has been deposited on a surface. By branching of hydrophobic restrictions, we have achieved the surface analogue of a piping system. A symmetry in the drop front wetted perimeter allows near equal volume divisions. The use of discrete drops allows manipulation hence greater flexibility. Dilution of analyte is prevented and any projected kinetics may occur unhindered by the fluid transport. Implementation of on-chip systems are more practical since the device does not require power and can be made re-usable. This study illustrates that at least 3 divisions can be performed sequentially on an 1.5 µL volume to effect near equal final volumes of approximately 180 nL. A division of carrier liquid volume by 1/23 enables multiple analysis on separate stations in one Lab-on-a-chip application.