Trapping probability analysis of a DNA trap using electric and hydrodrag force fields in tapered microchannels

This paper describes a quantitative analysis of the trapping probability for the DNA trap, which is a method of trapping and concentrating DNA in a tapered microchannel by electric and hydrodrag force fields. In order to calculate the trapping probability, a series of connections of triangle-shaped taper stages was used. The fluorescent intensity of trapped DNA molecules at each stage was measured. The trapping probability per stage was calculated from the distribution of the fluorescent increase rate along with the stage number. The trapping probabilities were measured as a function of DNA size, electric field, and average hydraulic velocity. The electric field that gives a trap probability of 0.5 was found to be proportional to the average hydraulic velocity for all DNA sizes. For all measured conditions and accuracy, the trapping probability was found to be determined only by the ratio of the electric field to the average hydraulic velocity. These results reveal that the DNA trap is not simply caused by balance between the dielectrophoresis and hydrodrag forces.