between assemblies printed at 10% EtOH and those at 15 and 20% is influenced by both the difference in growth rate, which leads to more particles by 10 seconds, and the influence of solvent on interfacial interactions between nanoparticles. EtOH, as a less polar solvent than water, would screen the charges of the CTA + modified AuNR surface less effectively. Furthermore, it was previously shown that the addition of ethanol to a concentrated aqueous dispersion of AuNRs could trigger their aggregation and assembly due to the stripping away of CTAC micelles from the nanoparticle interface and decreased screening of electrostatic repulsion due to reduced solvent polarity. This can not only accelerate the process of aggregation with PVP, but also lead to increased AuNR assembly. This could be further affected by the change in conformation of the polymer coils. From 10 to 20%(v/v) EtOH, the polymer radius decreases and the conformation takes on a more globule-like structure . There is no evidence of AuNR aggregation prior to printing, as non-specifically adsorbed AuNRs away from the printed assembly appear non-aggregated (Figure ), supporting a printing mechanism driven by PVP-mediated interactions between AuNRs and the glass substrate.