Ultrafast molecule sorting and delivery by atomic force microscopy

An atomic force microscope (AFM) is tailored to perform ultrafast electrophoretic differentiation of molecules on populations of <0.1 zeptomoles (10-22 moles) on the surface of a probe tip. The driving force for differentiation is a large electric field applied over the length of an AFM tip that results in enhanced differential mobilities stemming from the confinement of the water layer on the tip surface. In a demonstration on DNA oligonucleotides, a 5-mer and a 16-mer exhibit migration times of 15 and 5 ms, respectively, approximately five orders of magnitude faster than in conventional capillary electrophoresis. © 2006 American Institute of Physics.