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Full-Text Articles in Engineering

The Profound Photophysical Effects Of Organic Chromophore Connectivity And Coupling, David J. Walwark Jr Nov 2021

The Profound Photophysical Effects Of Organic Chromophore Connectivity And Coupling, David J. Walwark Jr

Nanoscience and Microsystems ETDs

Through-bond and through-space interactions between chromophores are shown to have wide-ranging effects on photophysical outcomes upon light absorption in organic molecules. In collapsed poly(3-hexylthiophene), through-space coupling creates hybrid chromophores that act as energy sinks for nearby excitons and favorable sites for molecular oxygen to dock. Upon excitation with visible light the highly-coupled chromophores react with the docked oxygen and subsequently do not quench nearby excitons as efficiently. In tetramer arrays of perylene diimide chromophores the central moiety through-bond connectivity is synthesized in two variants which exhibit vastly different single-molecule blinking behavior and theoretically-predicted electronic transition character. In the more-connected tetramer …


Silica Sol-Gel Control With High Voltage Contactless Electrodes, Jonathan C. Hebert Nov 2021

Silica Sol-Gel Control With High Voltage Contactless Electrodes, Jonathan C. Hebert

Nanoscience and Microsystems ETDs

High Voltage Contactless Electrodes (HVE) non-evasively modulates silica sol-gel reactions by redistributing charge in solution. HVE induces formation of local neutral band (LNB) strata (pseudo interfacial surfaces) where the gradient of potential is zero ∇𝜓𝜓=0. HVE LNB shape corresponds to solubility and ultimately sol-gel form. HVE silica sol-gel control works by localizing pH and creating conditions where silanol polymerization is biform; condensation by protonation (cathodic), or by deprotonation (anodic). Steric modified Poisson-Boltzmann equation is used to develop a theory on HVE control of silica sol-gel formation and a nucleate potential functional of potential 𝜓𝜓. Technologies developed during this research are …


The Physics Of Slot-Die And Gravure Coating Associated With Precision Thin Films And Coating Defects, Robert E. Malakhov Sep 2021

The Physics Of Slot-Die And Gravure Coating Associated With Precision Thin Films And Coating Defects, Robert E. Malakhov

Nanoscience and Microsystems ETDs

Enabling future printable and flexible electronic (PFE) devices and technologies requires overcoming the technical challenge of manufacturing precision thin films and features at scale. Coating- and print-feature functionality for PFEs is imparted with dispersed active particulate inks that provide electronic properties via slot-die coating, a pre-metered film-deposition process, and gravure printing, a high-throughput, precision process. Both are poised to be ideal manufacturing technologies for PFEs but require further research to understand particulate effects in defect formation and processability. Therefore, overcoming the technical challenges of precision, throughput, and the complexities of particulate inks is the purpose of this work. For slot-die …


Converting Parylene C Into A Thin Film Piezoelectric Material, Murali Manohar Duggina Jul 2021

Converting Parylene C Into A Thin Film Piezoelectric Material, Murali Manohar Duggina

Nanoscience and Microsystems ETDs

Thin-film piezoelectric materials are increasing in demand, but most materials are stiff ceramic materials. Polyvinylidene fluoride (PVDF) is a common polymer piezoelectric material, but it has limitations such as it requires post-processing steps to promote appropriate β-phase and it has a low operating and Curie Temperature, which limits its use in traditional microfabrication processing. The toxicity of PZT makes it incompatible with biomedical applications. Therefore, there is a need to develop a new class of polymer piezoelectric films that are compatible with current microfabrication methods. Parylene C (PA-C) is a chemical vapor deposited semi-crystalline polymer material with a nonsymmetric polymer …