title: "Biodrop" Evaporation and Ring-Stain Deposits: The Significance of DNA Length.
abstract: Small sessile drops of water containing either long or short strands of DNA ("biodrops") were deposited on silicon substrates and allowed to evaporate. Initially, the triple line (TL) of both types of droplet remained pinned but later receded. The TL recession mode continued at constant speed until almost the end of drop lifetime for the biodrops with short DNA strands, whereas those containing long DNA strands entered a regime of significantly lower TL recession. We propose a tentative explanation of our observations based on free energy barriers to unpinning and increases in the viscosity of the base liquid due to the presence of DNA molecules. In addition, the structure of DNA deposits after evaporation was investigated by AFM. DNA self-assembly in a series of perpendicular and parallel orientations was observed near the contact line for the long-strand DNA, while, with the short-stranded DNA, smoother ring-stains with some nanostructuring but no striations were evident. At the interior of the deposits, dendritic and faceted crystals were formed from short and long strands, respectively, due to diffusion and nucleation limited processes, respectively. We suggest that the above results related to the biodrop drying and nanostructuring are indicative of the importance of DNA length, i.e., longer DNA chains consisting of linearly bonded shorter, rod-like DNA strands.
authors.forename: Alexandros
authors.initials: A
authors.lastname: Askounis
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Takata
authors.affiliation: Institute for Materials and Processes, School of Engineering, The University of Edinburgh , King's Buildings, Robert Stevenson Road, Edinburgh, EH9 3FB, United Kingdom.
authors.forename: Khellil
authors.initials: K
authors.lastname: Sefiane
authors.affiliation: Institute for Materials and Processes, School of Engineering, The University of Edinburgh , King's Buildings, Robert Stevenson Road, Edinburgh, EH9 3FB, United Kingdom.
authors.forename: Vasileios
authors.initials: V
authors.lastname: Koutsos
authors.affiliation: Université Bordeaux, I2M, UMR 5295, F-33400 Talence, France.|CNRS, I2M, UMR 5295, F-33400 Talence, France.|Arts et Métiers ParisTech, I2M, UMR 5295, F-33400 Talence, France.
authors.forename: Martin E R
authors.initials: ME
authors.lastname: Shanahan
mesh_terms: D004247:DNA / Q000737:chemistry*; D007700:Kinetics; D012825:Silicon / Q000737:chemistry; D013499:Surface Properties; D014835:Volatilization; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D004247:DNA; D012825:Silicon