On-Chip Transportation and Mixing of Microsample Using Electrohydrodynamic Flow*

Microfluidic devices and lab-on-a-chip systems are critically helpful in a number of biological and biomedical applications such as cell culture, drug delivery, and immunoassays. Micro-sample transportation, typically driven by hydraulic or pneumatic actuators, is one of the most elemental functions in the microfluidic systems. However, the existing sample transportation modules are difficult to control and observe because the existing of non-linearity and air bubbles. Moreover the closed channels has limited transparency and are inaccessible to microrobotic end-effectors. This study aims to develop a novel flow governing device for active sample transportation and assembly using electrohydrodynamic force. The dielectric liquid is filled in the microchannel as the transfer medium, and the electrodes are vertically integrated on the sidewalls to avoid blockage of the optical path. The dielectric liquid can generate a powerful flow when subjected to high DC voltage, thus providing an on-chip hydraulic power source. The proposed system is more compact than microdevices driven by external fluid sources such as syringe pumps. In addition, the vertically filled electrodes allows for a clearer view for observation and manipulation by other microrobotic tools. The micro-sample transportation experiments confirm that the sample can be transported bi-directionally with the highest transportation speed of 15.68 mm/s. The experiments also suggest that multiple samples could be transported and assembled by controlling the fluid flow in different channels.