To further investigate the working theory that the assembly process is induced by a PVP-mediated destabilization of the AuNPs, the effect of the polymer molecular weight was studied. Polyvinylpyrrolidone of 10, 55 and 360 kDa (1 mg/mL) was used with a fixed EtOH amount of 20%(v/v) and laser power of 14 mW. An increase of the incubation time was observed as the molecular weight of PVP increased, although the assembly growth rate was not significantly affected (Figure Comparing the results of our previous work , where AuNS in aqueous solution were used, the effect of polymer size on the assembly process was the same, i.e, as the size increased, the incubation time also increased. Since the assembly of AuNRs in pure water has not been achieved so far, experiments using AuNS with 20%(v/v) EtOH were carried out in order to elucidate whether this phenomenon is due to the role of solvent or NP shape anisotropy. A decrease of the incubation time for printing of AuNS with added EtOH was observed, similar to the outcome with AuNRs, suggesting that this is a solvent-driven effect. Similar to AuNRs, the molecular weight of PVP played a significant role on the speed of AuNS assembly. For example, with a laser power 8.6 mW, incubation times of 9.89s±0.93 and 18.54s±2.51 for PVP360K and PVP10K (1 mg/mL) were obtained, respectively. As mentioned above, ethanol directly influences the conformation of the polymer and its Soret coefficient. The magnitude of this effect is molecular weight-dependent . In the case of poly9,9-dioctylfluorene (PFO), the concentration of the condensed conformation increases when reducing the solubility, being this concentration larger upon increase of the molecular weight. Following this logic, in the case of PVP, at 20%(v/v) EtOH there would be more condensed chains in the larger PVP360K than in a smaller one (PVP10K), which would explain a decrease in ST (more thermophilic) and a shorter incubation time. The influence of PVP10K concentration with a fixed EtOH concentration of 20%(v/v) was also studied. With increasing polymer concentration, the incubation time decreased from 4.69s±0.45 at 0.1 mg/mL and 2.4s±0.27 at 1 mg/mL. The increase in polymer concentration likely results in a faster ligand exchange, allowing the polymer to functionalize both gold and glass surface around the hot spot in less time. As the incubation time decreases, the radial growth rate shows a slight increase with increasing polymer concentration (Figure ).