Disclosed is a method and apparatus for the isolation of DNA or cell nuclei or a mixture thereof from cell samples in a CD device. The method includes treating a suspension of whole cells with a lysis reagent so as to lyse the cytoplasmic membrane and at least some of the nuclear membranes, and introducing the lysate into micro-channels of a microfabricated apparatus in which each of the micro-channels is provided with a barrier disposed in the channel to impede the passage or flow of DNA and cell nuclei while allowing the passage of liquid through the micro-channel so that a mesh comprising DNA is formed in the channel.