An electrofusion chip with a cell delivery system driven by surface tension

We have fabricated an electric cell fusion chip with an embedded cell delivery function driven by surface tension and evaluated its performance with several types of plant cells. The chip consists of a polydimethylsiloxane-based microchannel with a fusion chamber and gold-titanium (Au-Ti) electrodes. The velocity profiles of the microfluid in the channel and fusion chamber were calculated to predict cell movement, and the electric field distribution between the electrodes was also calculated in order to determine the appropriate electrode shape. The range of the fluid velocity in the fusion chamber is 20-50 νm s^-1 and the measured speed of the cells is approximately 45 νm s^-1, which is sufficiently slow for the motion of the cells in the fusion chamber to be monitored and controlled. We measured the variation of the pearl chain ratio with frequency for five kinds of plant cells, and determined that the optimal frequency for pearl chain formation is 1.5 MHz. The electrofusion of cells was successfully carried out under ac field (amplitude: 0.4-0.5 kV cm^-1, frequency: 1.5 MHz) and dc pulse (amplitude: 1.0 kV cm^-1, duration: 20 ms) conditions.