Trapping and immobilization of DNA molecules between nanoelectrodes

DNA is one of the most promising molecules for nanoscale bottom-up fabrication. For both scientific studies and fabrication of devices, it is desirable to be able to manipulate DNA molecules, or self--assembled DNA constructions, at the single unit level. Efficient methods are needed for precisely attaching the single unit to the external measurement setup or the device structure. So far, this has often been too cumbersome to achieve, and consequently most of the scientific studies are based on a statistical analysis or measurements done for a sample containing numerous molecules in liquid or in a dry state. Here, we explain a method for trapping and attaching nanoscale double-stranded DNA (dsDNA) molecules between nanoelectrodes. The method is based on dielectrophoresis and gives a high yield of trapping only single or a few molecules, which enables, for example, transport measurements at the single -molecule level. The method has been used to trap different dsDNA fragments, sizes varying from 27 to 8,416 bp, and also DNA origami constructions. We also explain how confocal microscopy can be used to determine and optimize the trapping parameters.