A nanowall array structure was fabricated on a quartz chip as a separation matrix of DNA fragments, and a 30 s separation was realized for a mixture of DNA fragments (48.5 and 1 kbp fragments) by applying the electric voltage. A longer DNA fragment migrates faster than a shorter one in a nanowall array chip, and it is completely different from the separation of DNA based on gel electrophoresis, nanopillar chips, and nanoparticle array chips. Although the result is similar to DNA separation by entropic trapping, it could not be fully explained by entropic trapping phenomena. Direct observation of single-DNA molecular dynamics inside a nanowall array structure indicates that both confined elongation and relaxation recoiling of a DNA molecule occur, and an elongated DNA molecule migrates faster than a recoiled DNA molecule. Numerical fitting of DNA molecular dynamics reveals that the balance between times for the transverse of a DNA molecule in the nanowall array chip and the relaxation-recoiling of a DNA molecule governs the separation of DNA.

We fabricated two different distributions of nanopillars–tilted and square distributions. There are difficulties in fabricating a chip containing these nanopillars, particularly in Ni plating and quartz bonding. We improved the Ni plating by applying stable electric current and the reliability of the quartz bonding. In nanopillars with a square distribution, DNA showed conformational changes, and did not show any reptile motion, but moved in a straight line in contrast with its behavior in nanopillars with a tilted distribution. Nanopillars with a tilted distribution acted effectively as sieves for DNA separation by size.

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Exploiting the nonequilibrium transport of macromolecules makes it possible to increase the separation speed without any loss of separation resolution. Here we report the arrangement of a nanostructure array in microchannels to control equilibrium and nonequilibrium transports of macromolecules. The direct observation and separation of macromolecules in the nanopillar array reported here are the first to reveal the nonequilibrium transport, which has a potential to overcome the intrinsic trade-off between the separation speed and resolution.

A sensing device for the detection of a very small amount of the deoxyribonucleic acid (DNA) with the order of femtoliter is described. Such a sensing device has metal electrodes with a 40nm gap, and is fabricated by low-cost technology with the conventional photolithography and anodic oxidation. Gold (Au) electrodes are used to fix DNA, and the electric currents between two electrodes are measured to detect the existence of DNA. The results indicate that the present device is promising as future very low-cost DNA analyzing chips.