Method of forming a structure upon a substrate

A method of forming a structure upon a substrate, the method comprising:

• providing a substrate upon a surface of which a plurality of electrically conductive pads are disposed;
• depositing fluid containing a dispersion of electrically polarizable nanoparticles onto the substrate such that at least a portion of a first one of the plurality of pads is in contact with the fluid;
• applying an alternating electric field to the fluid using a first electrode and a second electrode, the first electrode being positioned so as to provide an effective first electrode end position from which the electric field is applied, coincident with the deposited fluid, and spaced apart from the first pad by a distance, and the second electrode being in contact with the first pad, such that a plurality of the nanoparticles are assembled by dielectrophoresis to form a first elongate structure extending along at least part of the distance between the effective first electrode end position and the portion of the first pad;
• and
• continuing to apply the electric field to the fluid at least until the first elongate structure connects the first pad and the effective first electrode end position,
• wherein the method further comprises:
• depositing fluid containing a dispersion of electrically polarizable nanoparticles onto the substrate such that at least a portion of a further one of the plurality of pads is in contact with the fluid;
• and
• applying an alternating electric field to the fluid using the first electrode positioned so as to provide a further effective first electrode end position from which the electric field is applied, coincident with the deposited fluid and spaced apart from the further pad by a distance and a second electrode in contact with the further pad, such that a plurality of the nanoparticles are assembled by dielectrophoresis to form a further elongate structure extending along at least part of the distance between the further effective electrode end position and the portion of the further pad,
• wherein the second electrode is movable with respect to the first electrode and the substrate, and the method comprises bringing the second electrode into contact with first pad so as to cause the first pad to act as a continuation of the second electrode, and
• wherein each of the plurality of pads occupies an area of the substrate surface having a shape comprising at least one corner.