Biphasic Nanoparticle Inks for Direct Write Assembly of Three-Dimensional Periodic Structures

Novel nanoparticle inks have been created for the direct-write assembly of 3-D periodic structures with fine scale (∼ 10 mum) features. These nanoparticle inks are composed of two populations of nanoparticles defined by the type of dispersant used to stabilize them, either poly(acrylic acid)(PAA) or a comb polymer comprised of a PAA backbone and poly(ethylene oxide)(PEO) teeth (PAA/PEO). The PAA/PEO-coated nanoparticles remain stable, and hence behave as repulsive species in suspension under high ionic strength conditions or in the presence of oppositely charged polyelectrolytes. By contrast, PAA-coated nanoparticles aggregate under these same conditions, and hence behave as attractive particles. Mixtures of these two nanoparticle populations allow one to broadly tune the elastic properties of the resulting suspension either by varying their total volume fraction or ratio of attractive-to-repulsive species. The rheological properties of these biphasic mixtures were measured through shear viscometry, oscillatory shear rheology, and compressive rheology. Biphasic mixtures have shear elastic properties intermediary between repulsive glasses and attractive gels, yet the scaling of their elastic properties with respect to volume fraction is dominated by the gel phase. By contrast, their compressive yield stress exhibits a volume fraction dependence that varies systematically between that observed for glasses and pure gels. More importantly, the compressive-to-shear yield stress ratio exhibits a pronounced volume fraction dependence, such that biphasic mixtures of intermediate composition exhibit a greater resistance to pressure filtration (or jamming) during direct ink writing. Using these novel inks, 3-D periodic structures are patterned with features approaching 10 mum, which correspond to nearly an order of magnitude reduction in size compared to those produced from pure gel-based inks.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Science and Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Rao, Ranjeet Balakrishna

Contributors dc:contributor

• Jennifer Lewis

• Engineering, Chemical

Language dc:language

eng

Identifier

(MiAaPQ)AAI3337995

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/82833