Doctor of Philosophy (PhD)
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photonic crystal, hydrogel, computational model, fabrication, fluorescence microscopy, ultrasound
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Photonic crystal (PhC) hydrogels are a unique class of material that has tremendous promise as biomedical sensors. The underlying crystal structure allows for simple analysis of microstructural properties by assessing the diffraction pattern generated following laser illumination. The hydrogel medium provides elasticity, regenerability, and potential functionalization. Combining these two properties, photonic crystal hydrogels have the potential for sensing physical forces and chemical reagents using a low-cost, reusable platform.
The development of biomedical sensors using this material is limited due to the lack of a method to accurately predict the diffraction pattern generated. To overcome this, a computational model was developed specifically for PhCs and validated against existing analytical models and an existing electromagnetic scattering model in the literature. Assessment of its accuracy in comparison to existing analytical equations and a more generalized multiparticle scattering model in the literature, CELES, found clear alignment. Another challenge is the lack of a technique to assess the specific positions of each particle in the crystal structure non-destructively. To overcome this, a novel fabrication approach was created using fluorescent particles, allowing subsequent confocal fluorescence microscopy and analyses to extract per-particle position information. This technique was used to directly compare experimental, computational, and analytical results within a single sample.
To demonstrate a novel biomedical application of this material, ultrasound detection was chosen since it would be able to leverage the elastomeric structure of the PhC hydrogel as well as the ability to optically measure small changes in crystal microstructure. The sensitivity, frequency bandwidth, and limit of detection of fabricated PhC hydrogels were assessed using three ultrasound transducers. All transducers created a measurable optical response, with the limit of detection growing steadily with transducer frequency.
These results provide evidence that the platform can be utilized across a variety of biomedical disciplines. For biomedical imaging, this platform can be used for all-optical non-contact ultrasound sensing. For cell and tissue engineering, this platform can provide a novel approach for characterizing and monitoring contractile cells, such as cardiomyocytes. Finally, for environmental engineering, this platform can be used as a continuous monitoring solution for dangerous toxins in environmental waterways.
Sarwar, Mehenur, "Photonic Crystal Hydrogels: Simulation, Fabrication & Biomedical Application" (2022). FIU Electronic Theses and Dissertations. 5031.
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