The present invention relates to a microfluidic device for extracting and isolating DNA from cells. The device includes a support having an inlet port for receiving a sample containing a cell, an outlet port for dispensing DNA isolated from the cell, and a microfluidic channel disposed within the support and extending from the inlet port to the outlet port. The microfluidic channel includes a micropillar array, an inflow channel disposed between the inlet port and the micropillar array, and an outflow channel disposed between the micropillar array and the outlet port. The micropillar array includes micropillars spatially configured to entrap, by size exclusion, the cell, to immobilize DNA released from the cell, and to maintain the immobilized DNA in elongated or non-elongated form when hydrodynamic force is applied to the microfluidic channel. Systems and methods of making and using the device are also provided herein.