Method for repairing conductor tracks

A method of modifying an elongate structure, the method comprising:

• providing on a substrate an elongate structure formed of assembled electrically polarizable nanoparticles, the elongate structure including a narrow section to be modified;
• providing a fluid deposited onto the substrate, the fluid containing a dispersion of electrically polarizable nanoparticles and being positioned so that at least the narrow section of the elongate structure is immersed therein;
• and
• applying an AC voltage across a portion of the elongate structure that includes the narrow section using a first electrode in contact with the elongate structure at a first end of the portion and a second electrode in contact with the elongate structure at a second end of the portion, so as to:
• cause an alternating electric current to pass through the narrow section such that a break in the elongate structure is formed at the narrow section, the break being defined between a first broken end and a second broken end of the elongate structure, and then
• cause, when the break is formed, an alternating electric field to be applied to the fluid such that a plurality of the nanoparticles contained in the fluid are assembled to form a continuation of the elongate structure extending from the first broken end towards the second broken end so as to join the first and second broken ends;
• monitoring the current passing through the continuation of the elongate structure and continuing to apply the AC voltage across the portion of the elongate structure at least until the monitored current is equal to or greater than a target current;
• wherein the steps of:
• applying an AC voltage across a portion of the elongate structure that includes a narrow section,
• monitoring the AC amplitude of the current passing through the continuation of the elongate structure, and
• continuing to apply the AC voltage across a portion of the elongate structure at least until the monitored current amplitude is equal to or greater than a target current amplitude
• define one modifying cycle, and wherein the method further comprises:
• performing one or more further modifying cycles, for each of which each of the amplitude of the applied AC voltage and the target current amplitude is increased with respect to the previously performed modifying cycle.