Dielectrophoretic chip with multilayer electrodes and microcavity arrays for trapping and programmable releasing of single cells

Cell analysis usually involves a sequence of steps such as culture, separation, trapping, analysis and collection. Microfabricated system provides great potential to incorporate several steps of an assay into a single system. In present study, a dielectrophoresis (DEP) microdevice was developed for trapping cells and programmable releasing cells under single-cell level. The structure of DEP chip consisted of ITO top electrode, flow chamber, middle electrode on SU-8 surface, microcavity arrays of SU-8 and distributed electrodes at the bottom of microcavity. Trapping cells into microcavity array can be achieved by applying AC power to the top and middle electrodes due to the negative DEP force, in addition, releasing the trapped cells individually can be accomplished by switching the AC power to the top and bottom distributed electrodes. On the other hand, releasing all trapped cells in microcavities also can be performed by tuning the frequency of AC power to the positive DEP range and applying to the top and middle electrodes. The sequence of cell assay in the present DEP chip is described as follow, firstly, cells was trapped into microcavities by negative DEP, then; one can perform the cell analysis under single-cell level such as drug treatment or biomedical sensing on the chip without applying DEP voltage due to the enhancement of cell immobilization by microstructural effects. After the target cells have been identified based on the analysis results, the target cells can be individually released by control of bottom distributed electrodes. Finally, the rest trapped cells can be pulled out by positive DEP force constructed by top and middle electrodes and flashed away for the next run of cell analysis. In the experimental results, the capability of electrical manipulation successfully demonstrated by human promyelocytic leulcemia cells (HL-60). In general, the multi-step manipulations of cells can be easily programmed by control of electrical signal in our design, which provides an excellent platform technology for lab-on-a-chip (LOC) or micro-total-analysis-system (Micro TAS).