New York engineers have developed a novel method for assembling nanoparticles into three-dimensional structures that one day may be used to produce new nanoscale tools and machines. The work could be an important step in fulfilling the immense potential of nanotechnology because it gives scientists and engineers improved control and flexibility in the creation of materials for the manufacture of many nanoscale devices. The researchers used non-uniform AC electric fields generated by microfabricated electrodes — which create a motion known as dielectrophoresis — to stack latex, silica or graphite microparticles into two- and three-dimensional structures of prescribed lengths and composition, held together by the electrical field.