The objective of my research is to develop new surface optochemical sensors for studying cellular processes by investigating techniques to modify surface properties. The spectral characteristics of the modified surfaces and coatings are designed to show remarkable changes after interaction with analytes from biological fluids and cells. My studies focused on pancreatic cells and addressed the need for improved techniques to measure zinc release from pancreatic cells (chapter 3, 4) and to measure the metastasis potential of cancerous pancreatic cells (chapter 5). Chapter 3 describes the development of zinc sensing glass slides by conjugating a carboxylmodified ZnAF-2 to an amino functionalized glass surface. The sensor was used for the measurement of glucose-stimulated zinc ion release from cultured beta pancreatic cells with impact in diabetes research. In chapter 4 is described conjugation of the carboxyl-modified ZnAF-2 to antibody molecules (A2B5) that specifically recognize pancreatic cells. This enabled for the first time the use of targeted zinc sensors to monitor zinc release events from pancreatic cells. Chapter 5 describes development for the first time of a fluorescence sensor to measure the proteolysis activity of pancreatic cancer cells in microfluidic systems. The sensor was fabricated using a Layer by layer (LbL) deposition of polyelectrolyte. The sensor was based on Fluorescence Resonance Energy Transfer (FRET) between luminescent quantum dots (serve as donors) and rhodamine molecules (serve as acceptors) that are separated by multi-layers of polyelectrolytes. The microfluidic platform enables precise delivery of reactants to assemble the sensor and facilitate unique cellular assays of enzymatic activity and enzymatic expression on pancreatic cancer cells.

Thesis advisor: Willie J. Padilla / The field of metamaterials (MMs) has garnered a great deal of attention ever since the experimental demonstration of negative refractive indexes. Such an exotic response stemmed from the engineering capability of MMs, as they can obtain almost any optical responses at any given frequency by carefully structuring the geometries. There are countless examples where MMs have posed promising results in tailoring free space radiation. However, their usage beyond this common platform is far less explored. For examples, surface electromagnetic waves, which offer great potentials for future device applications, could be an intriguing place for the further development of metamateirals. In this dissertation, we study various MM configurations where the interplay between surface waves and metamaterials has a significant impact on the device performance. Firstly, Chapter 1 introduces some fundamental concepts of metamaterials and surface electromagnetic waves, and outline the fabrication, experiments, and characterization details. In Chapter 2, we investigate whether the effective optical parameters of MMs have the exact physical meaning as those of natural substances. Two types of MM resonators are studied, and we found the thickness of the host matrix plays a crucial role in such a homogenization process. Next, we present a computational and experimental study of MMs in conjunction with a novel gigahertz/terahertz transmission line, in Chapter 3. By optimizing the coupling between the MMs and the signal, information can be encoded. Chapter 4 presents a study of designing an extremely subwavelength magnetic MM. By maximizing the effective inductance and capacitance of the structure, the final geometry obtains a strong magnetic resonance with the size of merely λₒ/2000, where λₒ is the resonant wavelength. A novel time-domain spectroscopic method is also proposed to determine the frequency-dependent permeability of the samples. In Chapter 5, we characterize two hidden channels of MM perfect absorbers : scattering and generation of surface electromagnetic waves. In particular, we unveil lossy surface waves are generated during the process resulting in an enhancement of angular absorbance. The study provides a new insight to the working principle of MMAs. In Chapter 6, we investigate complementary MM structures that exhibit strong extraordinary optical transmission with higher transmission efficiency. We discover the origin of the fundamental mode is irrelevant to the Bloch modes. Lastly, we summarize all achievements and give an outlook in Chapter 7. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

Thesis advisor: Udayan Mohanty / Among the existing strategies to direct solar energy harvesting and storage, solar fuel production by photoelectrocatalysis promises a comparatively simple, low-cost route. The science behind this process is straightforward: stable semiconductors absorb sunlight and use the energy to excite charges, which then drive redox reactions at the surface. Careful studies of the photoelectrode surface provide important considerations in building a high-performance photoelectrode. Specifically, I focused on controlling the surface band alignment of Cu2O photocathode|water for hydrogen evolution reaction. A ZnS buried heterojunction is formed to improve the photovoltage. Then I focused on understanding the influence of chemical species on surface kinetics and energetics for water oxidation reaction. Two hematite photoanodes with preferably exposed {001} and {012} facets were examined. Further, I systematically studied three different types of surfaces, bare hematite, hematite with a heterogenized Ir water oxidation catalyst (WOC), and a heterogeneous IrOx WOC. While both WOCs improve the performance of hematite by a large margin, their working mechanisms are found to be fundamentally different. I also focused on utilizing surface photoexcited species to control product selectivity. Selective CO production by photoelectrochemical methane oxidation is successfully demonstrated. Detailed experimental investigations revealed that a synergistic effect by adjacent Ti3+ sites is the key to CO formation. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

The shape of a liquid's surface is determined by both the body force and surface force of the liquid. In this report, the body force is solely from the gravitational force. The surface force is generated from the movement of an elastic interface between the solid and liquid. To obtain the shape of the surface, both asymptotic analysis and numerical approaches are used in this report. The asymptotic analysis is applied on the potential flow. The initial conditions are chosen to be the function of the shape of the interface between the solid and liquid and the free stream velocity far away from the interface. The time dependent contributions from the fluid system are also considered. The initial condition changes according to the function of the calculated velocity potential. The numerical approach includes two parts: calculation the velocity potential and a formalism of the change of the system as time evolves. For the first part, two idealized vertical boundaries are utilized to give a unique solution of the Laplace equation. The boundary conditions are determined as the flow under linear viscosity. For the second part, the flow is first assumed to be a potential flow, and a boundary layer is considered to make the no-slip condition valid and to give a more precise approximation for the shear stress.

Les propriétés de surface, particulièrement microgéométriques, jouent un rôle essentiel dans tous les systèmes tribologiques. L’analyse de la répartition des efforts de contact dans l’interface entre surfaces rugueuses est indispensable à la prédiction du frottement, de l'usure, de l'adhérence, des résistances de contact électrique et thermique… De nombreux modèles ont été proposés ces dernières décennies pour prédire les efforts entre aspérités de surfaces rugueuses. Parmi ces modèles, les modèles statistiques sont majoritairement développés en considérant le contact ente une surface rugueuse équivalente, la surface somme - qui tient compte des microgéométries des deux surfaces en contact ainsi que de leur matériau - et un plan lisse. Cependant la validité de cette modélisation n’a pas été clairement démontrée. L’objectif de notre étude a été de développer un modèle statistique de contact entre deux surfaces rugueuses isotropes aléatoires puis de comparer les résultats obtenus pour ces deux surfaces avec ceux obtenus en considérant la surface somme définie classiquement à partir des deux surfaces rugueuses et un plan lisse. Les différences entre les résultats nous ont amenés à proposer une nouvelle modélisation de la surface somme. / Surface properties, particularly micro-geometry, play a key role in all tribological systems. The analysis of the distribution of contact forces in the interface between rough surfaces is essential for the prediction of friction, wear, adhesion, electrical and thermal contact resistance... Many models have been proposed during the last decades to predict the forces between asperities of rough surfaces. Among these models, statistical models are mainly based on the contact between an equivalent rough surface, the sum surface - which combines micro-geometry of the two surfaces in contact and their material - and a smooth plane. However, the validity of this model has not been clearly demonstrated. The aim of our study was to develop a statistical model of the contact between two random isotropic rough surfaces and then compare the results with those obtained by considering the classical sum surface. The differences between the results have led us to propose a new definition for the sum surface.

No description available.

Understanding and controlling the nature of interactions at interfaces between various materials and systems has always been of interest, but with the fast development and need of new technologies it has become crucial to employ these interactions for various applications that range from biosensing of analytes in bodily fluids and the environment, to the development of bio-compatibatible and bio-mimicking surfaces that can be used to successfully couple biological systems to artificial materials and also build models for understanding biological systems better. Self-assembled monolayers (SAMs) are organized molecular assemblies that are formed by spontaneous adsorption of a compound in solution to a surface. They can change the surface properties without the need of changing the physical properties of the bulk material. Formation of SAMs on different substrates was investigated and performed in the work described in the thesis to be used in the detection of nucleic acids and enzyme inhibitors, development of surfaces with anti-adhesive and anti-microbial properties, development of surfaces for directed and patterned cell adhesion, and the construction of artificial membranes that can be used for studying the interaction of membrane proteins and the discovery of new pharmaceuticals. The surface of gold substrates was modified with alkanethiol compounds in order to attach biomolecules such as nucleic acids and proteins which allowed the modified surface to be used as a biosensor. Binding interactions were detected by electrochemical impedance spectroscopy and surface plasmon resonance. A surface resonance sensor provided a platform for the detection of DNA and RNA oligonucleotide sequences and also the detection of one-nucleotide mismatches from the hybridization these oligonucleotides. The same sensor platform, but with a different surface modification, was used to covalently attach an enzyme whose inhibitors are used as therapeutic drugs and also as pesticides and nerve agents. The sensor was able to detect two of these inhibitors, which are used in the treatments of Alzheimer's disease, at a range of concentrations. This allowed the determination of binding affinity constants for the two inhibitors. The surface of gold was modified with functional groups in order to obtain inert surfaces with anti-adhesive properties with regard to the attachment of proteins. These surfaces are of interest in generating bio-compatible medical implants that can resist rejection from the host's immune system andor the formation of bacterial biofilms. The inert property was combined with anti bacterial properties by attaching an antibiotic which is known to kill bacteria by binding to the cell membrane. Following characterization of gold surfaces by contact angle measurements, ellipsometry, grazing angle FT-IR, cyclic voltammetry and electrochemical impedance spectroscopy, the surface of glass substrates was modified with similar functional groups, by switching to a different coupling ligand for the substrate. Alkoxysilanes were used to modify the surface of glass, which can also be used to modify other materials, such as polymers and stainless steel. Gold and glass surfaces were also modified with antibodies, other proteins, and other functional groups which favored or prevented cell adhesion. This led to the ability for patterned and directed adhesion, and differentiation of several cell lines. Preparation and chemical modification of magnetic beads and the ability to modify the bead surface created the possibility to grow and trap cells in a flow-through magnetic bioreactor, which will be used for the continuous production of metabolites and growth of tissue in a three-dimensional construct. Modification of gold substrates also led to the construction of artificial phospholipid membranes, whose composition can be controlled and most importantly can be used for the insertion and characterization of membrane proteins on a two-dimensional platform. This will allow for characterization of ligand-protein and protein-protein interactions with surface characterization techniques such as surface plasmon resonance and electrochemical impedance spectroscopy. The various surface modifications and applications described in this work underscore a general theme that the surface of many different materials can be modified by using the correct functional groups for the formation of the self-assembled monolayer on the substrate surface, thus obtaining the same surface properties without the need to change the physical and chemical properties of the bulk material.

聚（N-異丙基丙烯酸醯胺）（PNIPAM）微凝膠是一種内部有化学交联的三維網絡結構的軟膠體。這種微凝膠的物理性質是介於硬球膠體和超軟軟的星形聚合物或者膠束之間的。根據微粒的柔軟程度，微凝膠可以發生網絡互穿或者形變。因此塞滿微凝膠的體系的有效體積分數可以遠遠超過硬球系統裏的緊密堆積體積分數。這樣的系統會出現比硬球系统更加豐富的相行為。然而現在仍然缺乏對軟膠體系統在超過緊密堆積體積分數時變現的機構和性質的研究。特別是有些理論預測出的相行為仍然還沒被實際的實驗觀測的到。 / 本論文採用了一種新穎的方式去研究微凝膠體系的微流變，這種方法結合了粒子追蹤微流變和磁鑷系統。這種方法本質上是通過一種消逝波（產生於全內反射顯微鏡（TIRM）中的固液介面）作為入射光來探測靠近平直表面上事先植入的探針微粒（直徑為幾個微米）的位移。這個儀器通過記錄來自探針微粒的散射光強度來追蹤植入的探針微粒在垂直於固體水平面上的熱運動。對於位移的記錄可以達到十個納米的精度，使得它成為很靈敏的空間位置探測器。再者，通過添加了磁鑷系統，使得我們能夠有效地通過震蕩的力來在三維空間裏操控植入的微粒。通過控制探針微粒的運動，可以測量微凝膠懸浮液裏局部原位的粘彈性質。我們研究了濃度依賴和溫度依賴的PNIPAM微凝膠懸浮液的結構變化和相行為。 通過微流變的研究，讓我們第一次通過分析微凝膠懸浮液的粘彈性，確認觀測到了由有效體積分數導致的可逆轉的流體態-玻璃態-劉體態的相轉變過程。 / Soft colloids such as poly(N-isopropylamide) (PNIPAM)-based microgels are colloidal particles that consist of chemically cross-linked three-dimensional polymer networks. The physical nature of these microgel particles thus lies in between that of hard-sphere colloids, and ultrasoft star polymers as well as micelles. Due to the softness of the particles, microgels can interpenetrate or compress. As a result, microgels can be packed to effective volume fractions far above solid particles close packing, leading to the existence of much richer phase behavior when compared to simple hard colloidal particles. However, there is still a lack of knowledge on the structure and properties of soft colloid suspensions at and above close packing, and in particular some theoretically predicted phase behavior has not yet been reproduced by the experimental studies. / This thesis presents a novel approach to study the rheological properties of soft microgel suspensions using a combination of particle-tracking microrheology and magnetic tweezers. We essentially employ an evanescent wave (generated by a solid/liquid interface in the total internal reflection microscopy (TIRM)) as the incident light source to probe the displacement of an embedded probe particle (of a few micrometers diameter) near a flat surface. By measuring the scattered intensity, this technique allows tracking of the thermal motion of the embedded particle perpendicular to the solid surface to a precision of tens of nanometers, making it a highly sensitive spatial detector. Moreover, the integration of a magnetic driving force into the TIRM enables us to effectively manipulate the embedded particle in three dimensions by an oscillatory force so that the local viscoelastic properties of the microgel suspensions can be measured by resolving the particle motion. We investigated the concentration- and temperature-dependent on the structural ordering and phase behavior of PNIPAM microgel suspensions. Microrheology allows us, at a first time, to identify an effective volume fraction driven re-entrant liquid-glass-liquid phase transition by looking at the viscoelastic properties of the suspensions. We show that this result is related to the softness of the microgel particles under a confined condition, and discuss our findings in view of the existing theoretical predictions for soft particles. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Hua, Li. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references. / Abstracts also in Chinese. / 摘要 --- p.i / Abstract --- p.ii / Acknowledgement --- p.iv / Chapter 1 --- p.1 / Chapter 1.1 --- Introduction to colloids --- p.1 / Chapter 1.1.1 --- Phase transition in hard colloidal system --- p.2 / Chapter 1.1.2 --- Phase transition in soft colloidal system --- p.3 / Chapter 1.2 --- Overview of phase transition in microgels --- p.4 / Chapter 1.3 --- Simulation of soft colloids’ phase diagram --- p.8 / Chapter 1.4 --- Reference and Notes --- p.12 / Chapter 2 --- p.15 / Chapter 2.1 --- Overview of the microrheology methods --- p.15 / Chapter 2.1.1 --- Passive techniques of microrheology --- p.16 / Chapter 2.1.2 --- Active techniques for microrheology --- p.23 / Chapter 2.2 --- Microrheometer based on incorporating Magnetic Tweezers to Total Internal Reflection Microscopy --- p.29 / Chapter 2.2.1 --- Particle tracking system - TIRM --- p.30 / Chapter 2.2.2 --- Magnetic Tweezers as driven force --- p.32 / Chapter 2.2.3 --- Calibration of the magnetic force --- p.35 / Chapter 2.3 --- Reference and Notes --- p.37 / Chapter 3 --- p.44 / Chapter 3.1 --- Overview of the series of experiments --- p.44 / Chapter 3.2 --- PNIPAM microgel synthesis and characterization --- p.44 / Chapter 3.3 --- Microrheology of PNIPAM microgels suspension --- p.47 / Chapter 3.3.1 --- Volume Fraction dependence measurements --- p.49 / Chapter 3.3.2 --- Temperature depended measurements --- p.53 / Chapter 3.4 --- References and Notes --- p.55 / Chapter 4 --- p.56 / Chapter 4.1 --- Discussion and Conclusion --- p.56 / Chapter 4.2 --- Future Perspectives --- p.59 / Chapter 4.3 --- References and Notes --- p.61

No description available.

It is possible to drain slender containers filled with wetting liquids via capillary flows along the interior corners of the container. Usually the well established equations governing such flows demand numerical techniques. In the case of container draining unique boundary conditions resulting from local section geometry allow for a quasi-steady assumption and in turn permit analytical solutions. The quasi-steady assumption may also be employed for certain problems in which the corner flows cause passive capillary migration of the fluid within the container. The analytic solutions are useful because of the ease in which geometric effects may be observed. Container draining and capillary migration by means of corner flows are studied in a variety of container geometries. It is shown that careful selection of cross sectional shape can be used to maximize drain rates and minimize capillary migration times. Three-dimensional effects for these flows are investigated in tapering containers. Some simple micro-scale experiments are reported that provide confidence in the assumptions and application of the important boundary conditions that enable the solutions.