Dielectrophoresis refers to the force exerted on the induced dipole
moment of nanoparticles by an a.c. field. The induced dipoles interact
with the gradient of the non-uniform electric field and with each
other. Dielectrophoresis can be used for the assembly of different
types of nanoparticles in a variety of liquids without the undesired
effects caused by electro-osmosis and electrolysis59,60. Figure 4e shows
chains of gold nanoparticles, which were assembled from an aqueous
solution under an a.c. field of 95–96 V cm−1 (ref. 60). At higher voltage
the chains grew on the electrode in the regions of high field-intensity.
Owing to the strong attraction forces, the assembled structures
remained stable when the electric field was removed