Fig. 1
The pattern of DEP chip and the schematic cross section of DEP groove. For the fabrication of the DEP chips, a 300-nm-thick SiNx film was firstly grown directly on silicon substrate by plasma-enhanced chemical vapor deposition (PECVD), and then the SiNx film was covered with a photoresist film made by spin coating method. After baked, the photoresist film was exposed under UV light using the DEP mask and then was developed to remove the exposed photoresist, resulting in the appearance of clear DEP patterns. After the substrate was cleaned and baked again, a 20-nm-thick titanium (Ti) film and a 200-nm-thick gold (Au) film were successively deposited by sputtering. Finally, the unexposed photoresist film together with the Au/Ti film on its surface was removed by acetone, leaving Au/Ti DEP electrodes retained on the exposed area. The width and length of each DEP groove between the electrodes are 5 and 500 μm, respectively. The width of the electrodes is 500 μm