Cancer is the second leading cause of death in the world. It is therefore critically important to detect cancer in its early stage to significantly increase the survival rate of cancer patients. Circulating tumour cells (CTCs) are cancer cells that peel off from primary tumour and enter bloodstream in early stage of a cancer, and thus it has been established that these CTCs are reliable targets for early cancer diagnosis. However, background signal reduction and optimization of CTC capturing mechanisms are still significant challenges in CTC detections with high sensitivities and accuracies. To this end, we have developed an aptamers and dendrimers based ultra non-fouling microfluidic detection system for sensitive detections of circulating tumour cells. More specifically, we demonstrate a simple strategy to bind PDMS and SU-8 surfaces in order to prepare a hybrid microfluidic device and subsequently modify both surfaces simultaneously using poly(amidoamine) (PAMAM), a highly hydrophilic dendrimer to improve non-fouling properties of the hybrid microfluidic channel. The resulting hybrid microfluidic system shows a remarkable non-specific adsorption suppression of 99.7% when tested with hydrophobic microbead suspension, an ultra non-fouling performance that has not been reported before. This is significantly important for detections with high sensitivities. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and water contact angle are used to characterize and confirm surface modifications. In addition, we investigate the combined effects of surface properties on surface non-fouling performance to both live and dead cells. (3-aminopropyl)-trimethoxysilane (APTMS), carboxyl functionalized PAMAM dendrimer (PAMAM-COOH) and amino functionalized PAMAM dendrimer (PAMAM-NH2) are used to provide different surfaces with various surface hydrophilicity, electric charge and roughness. We show that electric charge of a surface is the most important factor influencing non- specific adsorption of live cells to the surface while hydrophilicity/hydrophobicity of a surface is the most important factor for dead cells. Atomic force microscopy, water contact angle and microscopy are used to characterize and confirm surface modifications. To further exploit and improve capturing efficiency of target cancer cells, we investigate the effect of the length of spacers that tether capturing aptamer to the microfluidic surfaces on capturing performance of CCRF-CEM circulating tumour cells. Aptamers with different lengths of thymine base spacers are immobilized onto PAMAM dendrimer modified surfaces in microfluidic channels. We demonstrate that ten thymine bases spacer has the best length for sgc8 aptamer to form its secondary structure for CCRF-CEM cell capture. Water contact angle, and microscopy are used to characterize and confirm surface modifications. Taken together, the results of this study significantly highlight the importance of different considerations on surface modification and its optimizations when designing a microfluidic system for high sensitivity detection and biosensing applications.

Le but de cette thèse et de la recherche associée est une démonstration des avantages d’une combinaison de propriétés inhabituelles de nanostructures plasmoniques avec des aspects parmi les plus intéressants de l’optique non-linéaire. Pour cet effet, la modélisation analytique et numérique a été combiné avec le travail expérimental, qui comprenait la production de nanostructures et les mesures effectuées au moyen de la microscopie confocale non-linéaire résolue en polarisations et de la technique Z-scan modifiée (nommée “f-scan”).Il a été montré que l’anisotropie efficace de génération de seconde-harmonique dans les cristaux plasmoniques (formés par des réseaux rectangulaires de cavités tétraédriques sur une surface d’argent) peut être contrôlée par un choix approprié des paramètres de maille. Il a aussi été montré que cette anisotropie provient principalement d’une structure de bande photonique elle-même anisotrope, présentant une bande interdite plasmonique avec des états plasmoniques en bord de bande, permettant de renforcer le champ électrique local. Les arrangements chiraux bidimensionnels de nanoparticules triangulaires d’or, forment des “meta-molécules” plasmoniques énantiomériques, ont été analysés par microscopie non-linéaire à la lumière polarisée circulairement et par modélisation numérique, révélant un fort effet chiroptique par génération de seconde harmonique en rétro-réflexion. La petite taille des énantiomères uniques permet de créer “des filigranes” (“watermarks”) codés par la chiralité des meta-molécules, qui peuvent être lu par imagerie de la génération de seconde harmonique excitée par un rayon polarisé circulairement. Les caractéristiques quantitatives de la non-linéarité optique du troisième ordre et de l’efficacité d’absorption saturable des solutions aqueuses de fragments de graphène et de graphène dopé par des nanoparticules d’or a été effectuée par une nouvelle technique “f-scan”, qui a été créée et développée par incorporation d’une lentille à distance focale accordable dans une technique de Z-scan traditionnelle. Ces études ont montrées que le graphène présente une absorption saturable ultra-rapide très efficace, qui est parfois convertie en absorption saturable inverse. Il apparaît alors qu’une décoration du graphène par des nanoparticules d’or peut causer une légère amélioration du paramètre d’efficacité d’absorption saturable dans la plage spectrale de leurs résonances plasmoniques. En résumé, cette thèse présente une variété de propriétés optiques non-linéaires apparaissant dans les nanostructures plasmoniques. Différentes possibilités de contrôle de ces propriétés au moyen d’une démarche de nano-ingénierie, soutenue par des modélisations à la fois analytique et numérique ont été démontrées et analysées. Ces travaux ouvrent la voie à la fabrication et à l‘optimisation sur mesure de nouveaux nano-matériaux et nano-dispositifs photoniques reposant sur des effets de nano-plasmonique non-linéaire. / The aim of this thesis and the underlying research work is to demonstrate the benefits emerging from combination of the peculiar properties of plasmonic nanostructures with the most interesting aspects of nonlinear optics. For this purpose, analytical and numerical modeling was combined with experimental work, which included nanofabrication and measurements performed by means of polarization-resolved nonlinear confocal microscopy and by modified Z-scan technique (called "f-scan").It has been shown that the effective anisotropy of the second-harmonic generation in plasmonic crystals (formed by rectangular arrays of tetrahedral recesses in silver surface) can be controlled by proper choice of lattice constants. It also has been shown that this anisotropy arises mainly from the anisotropic photonic band structure, exhibiting plasmonic band gap with plasmonic band edge states, enabling enhancement of the local electric field.Two-dimensional chiral arrangements of triangular gold nanoparticles, forming plasmonic enantiomeric "meta-molecules", have been studied by nonlinear microscopy operating with circularly polarized light and by numerical modeling, revealing strong chiroptical effect in backscattered second-harmonic radiation. Small size of individual enantiomers allows to create "watermarks", encoded by the chirality of meta-molecules, which can be readout by imaging of second-harmonic generation excited by circularly polarized laser beam.Quantitative characterization of the third-order optical nonlinearity and saturable absorption efficiency of aqueous solutions of graphene and gold-nanoparticle decorated graphene has been performed by novel "f-scan" technique, which has been created and developed by incorporation of a focus-tunable lens into traditional Z-scan. These studies have shown that the graphene exhibits very efficient ultrafast saturable absorption, which is occasionally suppressed by reverse saturable absorption. Moreover, it turns out that decoration of graphene by gold nanoparticles may cause a slight improvement of the saturable absorption efficiency parameter within spectral range of their plasmon resonances.In summary, the following thesis presents various nonlinear optical properties of plasmonic nanostructures. Different possibilities of controlling these properties by means of nano-engineering, supported by analytical and numerical modeling, is also analyzed and demonstrated. This work opens up new perspectives for fabrication and rational design of novel photonic nano-materials and nano-devices based on nonlinear nanoplasmonic phenomena.

We propose the use of a small unmanned aerial vehicle (UAV) equipped with temperature, pressure, and relative humidity sensors to estimate sensible and latent heat fluxes over an active agricultural area in east-central Mississippi. The Bowen ratio method is applied to vertical soundings from the surface to 120 meters at 10-meter intervals. A number of flights were conducted at Mississippi State University during the late stages of the growing season with the purpose of obtaining heat flux estimates over different land surface/cover types. Results show that the UAV platform is able to provide reasonable heat and moisture flux estimates, and that the fluxes show substantial variability among different land cover types over a small spatial scale. Future work must be done to quantify the diurnal and seasonal changes in heat flux estimates over various crop types and investigate flight plans and sensor mounting options to maximize sensor precision.

The value of the surface charge density of polypropylene reported in literature has a three order of magnitude discrepancy. Nauruzbayeva et al report a 0.7nCcm−2 as the surface charge density of polypropylene as measured using the charge of electrified droplets[1]. Meagher and Craig reported result 111nCcm−2 as estimated by electric double layer theory from colloidal probe Atomic force microscopy (AFM) force spectroscopy [2]. We show that oxidation of hydrophobic surfaces as a potential mechanism in origin of these surface charges. Using colloidal probe AFM We measured the surface charge densities of Teflon AF, perfluorodecanethiol, Perfluorodecyltrichlorosilane(FDTS), Octadecyltrichlorosilane, polystyrene, and polypropylene. Also, The pH dependence of the surface charge density for FDTS was studied and it shows the behavior expected of a weak acid in response to pH. We suspect that the origin of the surface charges is mostly likely impurities or surface oxidation. We conclude that the electrometer and dispensed droplets approach cannot detect these charges because of the process of de-wetting all the surface be neutralized to maintain charge neutrality. This explanation supports Nauruzbayeva et al claims about surface bound charges[1].

No description available.

No description available.

Zirconia has been established as a promising material for dental implants. Various surface treatment methods have been utilized to promote better osseointegration and improve the success rate of dental implants. However, a better understanding of the influences of topographic characteristics on cell attachment, proliferation, and differentiation is needed. Different surface topographic zirconia specimens, As sintered, Mild rough, Moderate rough, and Rough zirconia groups were fabricated with sandblasting method in various distances and stages. The surface texture, microstructure, and wettability were inspected with the optical profiler, SEM, and contact angle measurement respectfully. Human primary osteoblast cells were cultured on the four groups of zirconia with different surface modifications in 24 well plates and on plates without test material as control. Crystal violet and triton X-100 solution were used to evaluate cell attachment efficiency at 9 hours and proliferation rate at 7, 14, and 21 days after seeding. ALP activity was measured with fluorometric assay. The expression of osteocalcin was measured with an ELISA kit. Alizarin red staining was conducted to evaluate the mineralization. The cell morphologies were inspected under SEM after cell fixation and critical point drying process. The data were analyzed with one-way ANOVA for experiment on each time interval and two-way ANOVA for all time points. Tukey post hoc test was used for pairwise comparison. P value < 0.05 was considered statistically significant. Topographic parameters and contact angle measured in As sintered, Mild rough, Moderate rough, and Rough surface groups were as follow: Sa = 0.23, 0.50, 2.13, 5 µm, Sal = 49.88, 21.20, 30.42, 49.87 µm, Sdq = 64.64, 248.60, 511, 734.66 µm/mm, Sk = 0.7, 1.54, 4.19,16 µm, Spk = 0.31, 0.64, 1.47, 5.13 µm, Svk = 0.35, 0.71, 5.96, 6.18 µm respectively, and contact angle = 64.6°, 55.2°, 43.5°, 38.6° respectively. The result showed that Rough zirconia group induced the highest cell attachment efficiency at 9 hours (p<.001). As sintered zirconia group promoted significant cell proliferation rate at 21 days (p<.001) while Rough zirconia group drastically down-regulated cell proliferation (p<0.001). The most elevated levels of ALP, osteocalcin, and mineralization expressions at 21 days were found in the Moderate rough group with significant differences (p<.001, p<.001, p<.001 accordingly) Within the limitations of this in vitro study, it can be concluded 1) the modified microroughened zirconia surfaces of Sa 5 µm would promote human osteoblast attachment but down-regulate cell proliferation, 2) the As sintered zirconia surface would stimulate cell proliferation, and 3) the microroughened surfaces of Sa 2 µm would up-regulate osteoblast differentiation. These findings could be incorporated into designing and fabricating the dental implant surfaces for optimal osseointegration.

<p dir="ltr">There is a plethora of applications that require chemical patterning on the molecular scale. While the surface science community has made tremendous progress in achieving this level of control on hard, crystalline interfaces, significant challenges are associated with extending this progress to less “perfect” systems such as soft, amorphous interfaces. Applications ranging from soft robotics and wearable electronics to regenerative medicine often utilize polymeric materials such as polydimethylsiloxane (PDMS) and hydrogels. These materials have advantageous properties, including biocompatibility and mechanical tunability. Biological applications, for example, often require the display of functional groups with precise spatial resolution. Cellular behavior is dictated by biochemical and biophysical cues in the extracellular matrix; therefore, substrate properties, including stiffness and ligand density, must be independently tunable. Soft, polymeric materials are highly heterogenous with pore sizes ranging from 10 nm to 1 µm and hence, particularly difficult to pattern below the length scale of substrate heterogeneity. Furthermore, deconvolving mechanical properties such as elastic modulus from the density of surface-active functional groups is especially challenging, with softer materials typically corresponding is lower ligand densities. Additionally, many traditional surface science characterization and patterning methods are incompatible with soft interfaces (e.g. amorphous surface structure, low mechanical strength, hydrated environment). Recently, we have reported a method capable of achieving high-resolution chemical patterning of PDMS and hydrogels. Long studied within the scanning probe community, amphiphiles with long alkyl chains self-assemble into lying down stripe phases on highly ordered pyrolytic graphite (HOPG), generating 1-nm-wide stripes of functional headgroups between 5-nmwide stripes of exposed alkyl chains. Stripe phases of functional diacetylenes (DA) are photopolymerized, producing a polydiacetylene backbone that tethers together adjacent molecules, generating a PDA film on HOPG (sPDA). We have shown that PDA films on HOPG can be transferred to PDMS as well as polyacrylamide hydrogels. When PDMS is cured in contact with sPDAs, the PDA backbones can act as a site for hydrosilylation, the same reaction responsible for PDMS curing, covalently linking sPDAs to the PDMS mesh. Careful exfoliation reveals nm-scale functional patterns on the surface layer of PDMS. 10 Here, we examine the impact of PDMS structural components on the efficiency of interfacial reactions between sPDAs and the PDMS network. We also illustrate the impact of PDAfunctionalized PDMS on the adhesion and spreading behavior of C2C12 murine myoblasts.</p>

In the past several years, the Defense Advanced Research Projects Agency (DARPA) has sponsored two Grand Challenges, races among autonomous ground vehicles in rural environments. These vehicles must follow a course delineated by Global Positioning System waypoints using no human guidance. Airborne LIDAR data and GIS can play a significant role in identifying barriers and least cost paths for such vehicles. Least cost paths minimize the sum of impedance across a surface. Impedance can be measured by steepness of slope, impenetrable barriers such as vegetation and buildings, fence lines and streams, or other factors deemed important to the vehicle's success at navigating the terrain. This research aims to provide accurate least cost paths for those vehicles using airborne LIDAR data. The concepts of barrier identification and least cost path generation are reviewed and forty-five least cost paths created with their performance compared to corresponding Euclidean paths. The least cost paths were found superior to the corresponding Euclidean paths in terms of impedance as they avoid barriers, follow roads and pass across relatively gentler slopes. / Master of Science

Geometrical modeling is a crucial aspect of simulations involving manufactured objects. Apart from the pure construction of curves and surfaces, the analysis of their quality is equally important in the design and manufacturing process. In computer-aided simulation, the original freeorm surfaces need to be tessellated into triangulated surfaces before the simulation procedure. To concurrently and interactively visualize the results from both simulation and surface interrogation in a virtual environment, I propose two novel surface interrogation algorithms for triangulated surfaces instead of the traditional freeorm surfaces. The novel algorithms are interactive and immersive versions of two well-established surface interrogation techniques ? reflection lines and generalized focal surfaces. These two algorithms have been designed to overcome some limitations of the traditional approaches and make them available for interactive and immersive applications. For reflection lines, the new algorithm maps the triangulated surface onto the light plane so that the computation of distance between reflection ray and light line in three dimensions can be reduced to computation of intersections between light lines and triangle edges in two dimensions, simplifying the computation. For generalized focal surfaces, the new algorithm estimates curvature by simple computation of the derivatives of a3rd degree triangular Bézier patch on each triangle and removes the requirement for a minimum number of neighbor points and implicit requirements on how the neighbor points are distributed. Proposed future work on real-time rendering of surface interrogation using a texture mapping technique is discussed.