Multicomponent films based on nanoparticle dispersions have a wide range of applications, including antimicrobial coatings for medical instruments, conductive textiles for flexible electronics, anti-reflective coatings for optical devices, paints for humid environments that are resistant to mold growth, and drug-loaded coatings for medical implants. Often, there is a need to spatially control location of certain components in the film. For example, silver nanoparticles can be used to impart antimicrobial activity to paints, but this component is expensive and may only be needed in the top few layers of the coating, not throughout the entire film. In principle, evaporative drying of multicomponent dispersions can be used to create films with a prescribed vertical concentration profile in a one-step process. In this talk, I will present our recent results from atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS) on films prepared from binary colloidal dispersions containing large and small particles of varying size and initial volume fraction. Our results show evidence of different types of stratification behavior, including large-on-top (e.g., large particles migrating to the top surface of the film), small-on-top, and “sandwich”-like layering. I discuss these results in terms of recent theories for stratification during evaporative drying. Additionally, I will present recent collaborative results on evaporative assembly of functionalized nanoparticles can yield striking dual-scale hierarchical structures. Regular microscale stripes of nanoparticle monolayers with hexagonal nanoscale order are obtained on physically and chemically homogeneous substrates through evaporation of a suspension of DNA-functionalized nanoparticles with a charged shell. The stripe width, spacing and nanoparticle ordering can be controlled by varying nanoparticle concentration and can be described by a simple analytical model. Our results indicate that the interplay between “stick-slip” motion of the droplet contact line and Coulombic and steric nanoparticle interactions control the formation of the observed structures.
Surita R. Bhatia received her B.Ch.E. in Chemical Engineering from the University of Delaware and her Ph.D. in Chemical Engineering from Princeton University, and she completed her postdoctoral training at the Centre National de la Recherche Scientifique (CNRS)/Rhodia Complex Fluids research laboratory. She is a faculty member in the Department of Chemistry at Stony Brook University. She began her independent research career at the University of Massachusetts Amherst, where she was a Professor of Chemical Engineering, Adjunct Professor of Polymer Science and Engineering, and Associate Director of the Institute for Cellular Engineering. She is a recipient of an NSF CAREER Award, a Dupont Young Professor Award, and a 3M Non-tenured Faculty Award, and a 2018 American Institute of Chemical Engineers (AIChE) Women’s Initiatives Committee Award for Outstanding Contributions to Chemical Engineering. Prof. Bhatia also has strong interests in mentoring, education, undergraduate research, and diversity in STEM fields. She has served as PI on three NSF Research Experiences for Undergraduates (REU) sites, is a recipient of the AIChE WIC Mentorship Excellence Award, was an invited participant in the 2009 National Academy of Engineering “Frontiers of Engineering Education” Symposium, and was an invited participant to the 2011 NSF/AAAS Workshop on Gender Diversity in Nanoscience Fields.
Attend via Zoom: https://stevens.zoom.us/j/96875673368.