Ewod based microfluidic system with coplanar electrodes for parallel DNA ligation of ultramicro volume

This paper reports the completion of a parallel ultramicro-volume DNA ligation processes using a coplanar electrode type of electrowetting-on-dielectric (EWOD) microfluidic system. The droplets, containing DNA, a ligation enzyme and a multi-salt reaction buffer, served to complete the ligation using a developed EWOD system. In order to reduce the effect from environment, so the concept of core-shell droplet was used in this study. Droplets of ultramicro volume (0.3 muL) were successfully generated from reservoirs between one plate with coplanar electrodes and another plate with a hydrophobic surface free of electrodes. In one successful cloning, the total usage of reagents in an ultramicro-volume EWOD chip was 2.1 muL; no volume was wasted, in comparison with 85% waste with the standard protocol (15 muL). The results also show that the four parallel DNA ligation processes were accomplished without damage to the chip surface and without biomaterial annulment.