Coarsening behavior of Au nanoparticles (AuNPs) embedded in a liquid crystalline lipid (1,2-dioleoyl-3-trimethylammonium-propane, DOTAP) membrane was investigated by heat treating the AuNP-embedded DOTAP membrane at 80 degrees C with 15% and 80% relative humidity (RH). The coarsening rate was (D) to approximately t0.6 regardless of the humidity; however, the spatial distribution and the coarsening mechanism differed depending on the humidity. In addition, extended treatment at 15% RH resulted in formation of large polygonized AuNPs from the lipid segregation.