Matching Items (2)
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Description
The advancements in additive manufacturing have made it possible to bring life to designs

that would otherwise exist only on paper. An excellent example of such designs

are the Triply Periodic Minimal Surface (TPMS) structures like Schwarz D, Schwarz

P, Gyroid, etc. These structures are self-sustaining, i.e. they require minimal supports

or no supports

The advancements in additive manufacturing have made it possible to bring life to designs

that would otherwise exist only on paper. An excellent example of such designs

are the Triply Periodic Minimal Surface (TPMS) structures like Schwarz D, Schwarz

P, Gyroid, etc. These structures are self-sustaining, i.e. they require minimal supports

or no supports at all when 3D printed. These structures exist in stable form in

nature, like butterfly wings are made of Gyroids. Automotive and aerospace industry

have a growing demand for strong and light structures, which can be solved using

TPMS models. In this research we will try and understand some of the properties of

these Triply Periodic Minimal Surface (TPMS) structures and see how they perform

in comparison to the conventional models. The research was concentrated on the

mechanical, thermal and fluid flow properties of the Schwarz D, Gyroid and Spherical

Gyroid Triply Periodic Minimal Surface (TPMS) models in particular, other Triply

Periodic Minimal Surface (TPMS) models were not considered. A detailed finite

element analysis was performed on the mechanical and thermal properties using ANSYS

19.2 and the flow properties were analyzed using ANSYS Fluent under different

conditions.
ContributorsRaja, Faisal (Author) / Phelan, Patrick (Thesis advisor) / Bhate, Dhruv (Committee member) / Rykaczewski, Konrad (Committee member) / Arizona State University (Publisher)
Created2019
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Description
Environmentally responsive hydrogels are one interesting class of soft materials. Due to their remarkable responsiveness to stimuli such as temperature, pH, or light, they have attracted widespread attention in many fields. However, certain functionality of these materials alone is often limited in comparison to other materials such as silicon; thus,

Environmentally responsive hydrogels are one interesting class of soft materials. Due to their remarkable responsiveness to stimuli such as temperature, pH, or light, they have attracted widespread attention in many fields. However, certain functionality of these materials alone is often limited in comparison to other materials such as silicon; thus, there is a need to integrate soft and hard materials for the advancement of environmental-ly responsive materials.

Conventional hydrogels lack good mechanical properties and have inherently slow response time, important characteristics which must be improved before the hydrogels can be integrated with silicon. In the present dissertation work, both these important attrib-utes of a temperature responsive hydrogel, poly(N-isopropylacrylamide) (PNIPAAm), were improved by adopting a low temperature polymerization process and adding a sili-cate compound, tetramethyl orthosilicate. Furthermore, the transition temperature was modulated by adjusting the media quality in which the hydrogels were equilibrated, e.g. by adding a co-solvent (methanol) or an anionic surfactant (sodium dodecyl sulfate). In-terestingly, the results revealed that, based on the hydrogels’ porosity, there were appre-ciable differences when the PNIPAAm hydrogels interacted with the media molecules.

Next, an adhesion mechanism was developed in order to transfer silicon thin film onto the hydrogel surface. This integration provided a means of mechanical buckling of the thin silicon film due to changes in environmental stimuli (e.g., temperature, pH). We also investigated how novel transfer printing techniques could be used to generate pat-terned deformation of silicon thin film when integrated on a planar hydrogel substrate. Furthermore, we explore multilayer hybrid hydrogel structures formed by the integration of different types of hydrogels that have tunable curvatures under the influence of differ-ent stimuli. Silicon thin film integration on such tunable curvature substrates reveal char-acteristic reversible buckling of the thin film in the presence of multiple stimuli.

Finally, different approaches of incorporating visible light response in PNIPAAm are discussed. Specifically, a chemical chromophore- spirobenzopyran was synthesized and integrated through chemical cross-linking into the PNIPAAm hydrogels. Further, methods of improving the light response and mechanical properties were also demonstrat-ed. Interestingly, such a system was shown to have potential application as light modulated topography altering system
ContributorsChatterjee, Prithwish (Author) / Dai, Lenore L. (Thesis advisor) / Jiang, Hanqing (Thesis advisor) / Lind, Mary Laura (Committee member) / Yu, Hongyu (Committee member) / Yu, Hongbin (Committee member) / Arizona State University (Publisher)
Created2015