As discussed in the methods section, the AuNR dispersion is illuminated with a focused 532 nm laser. Once the laser is on, the absorption of light by the AuNRs creates a thermal gradient pointing towards the hot region. According to their thermophoretic mobility DT, species in the solution will be driven to hotter or colder areas. Polyvinylpyrrolidone coils, in the presence of ethanol, are directed towards the hot spot along with the NPs (Figure ), while other species in the solution, such as the mentioned ethanol and CTA + molecules migrate away from the laser spot. In the hot zone, PVP coils, due to their strong binding affinity for the gold , adsorb onto the exposed areas of the surface (CTA + concentration is kept below the CMC 1.3 mM ), leading to the irreversible assembly and deposition of the AuNRs at the substrate surface.