High frequency acoustomicrofluidic platform for controlling morphogenesis, orientation, and dimensionality of crystals

Ahmed, H 2018, High frequency acoustomicrofluidic platform for controlling morphogenesis, orientation, and dimensionality of crystals, Doctor of Philosophy (PhD), Engineering, RMIT University.


Document type: Thesis
Collection: Theses

Title High frequency acoustomicrofluidic platform for controlling morphogenesis, orientation, and dimensionality of crystals
Author(s) Ahmed, H
Year 2018
Abstract Crystal engineering of three (3D) and two (2D) dimensional crystalline materials can be used for a wide range of applications, such as in drug delivery systems, electronics, energy and catalysis. Alteration of the crystal struc- ture, morphology, orientation, and dimensionality is highly desirable given that different crystalline structures of the same molecule has a direct influence on its physicochemical and pharmacokinetic properties. In this study we report the first instance of the use of a high frequency acoustomicrofluidic platform, in the MegaHertz (MHz) scale, for production and tuning an array of crystal properties including crystal morphology, polymorphism, orienta tion, and dimensionality. We first demonstrate a novel acoustically-driven micronization platform, which, due to its unique ability to access intermediate evaporation regimes (on the order of 10^-5 l/h), is capable of producing novel crystal structures and morphologies of 3D crystals in both model in- organic and organic systems that have yet to be reported. Later on, we report a high frequency acoustically-driven microcentrifugation platform that facilitates fast convective solutal transport, allowing freestanding MOF crys- tals to be synthesized in as short as 5 minutes. The crystals were not only highly oriented due to long-range out-of-plane superlattice ordering aided by molecular dipole polarization under the acoustoelectric coupling, but also simultaneously activated during the synthesis process. Furthermore, we move on to illustrate the ability to produce 2D crystals from their layered 3D bulk counterparts using a unique ultrafast solvent-free two-step multiscale exfoliation mechanism that exploits the piezoelectric nature of a number of these materials to trigger electrically-induced mechanical failure across weak grain boundaries associated with the crystal domain planes. In particular, we demonstrate that microfluidic nebulisation using high frequency acoustic waves exposes a bulk 3D crystalline piezoelectric material such as molybdenum disulphide (MoS2) to a combination of extraordinarily large mechanical acceleration ( 10^8 m/s2) and electric fields ( 10^8 V/m) such that they are rapidly cleaved into nanosheets that predominantly comprise single layers, thus constituting a continuous, rapid and high throughput chip-scale method that opens new possibilities for scalable production and spray coating.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Engineering
Subjects Acoustics and Noise Control (excl. Architectural Acoustics)
Energy Generation, Conversion and Storage Engineering
Composite and Hybrid Materials
Powder and Particle Technology
Keyword(s) Acoustics
2D mateials
crystallography
Metal organic frameworks
catalysis and energy storage
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Created: Wed, 28 Nov 2018, 10:46:11 EST by Anna Koh
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