Novel Metal and Silicon Oxide Engineered Substrates to Control Cell Alignment

Engineered biomaterials with micron- and sub-micron-scale topographical features are designed to mimic the in vivo functions of extracellular matrix (ECM) on promoting desirable biological changes by manipulating the behaviors of cells. Three newly developed silicon oxide-based substrates, and their effect on the alignment behavior of biological cells was investigated. All substrates were fabricated using a technologically advanced integrated circuit (ICs) based technique of chemical-mechanical polishing (CMP). These substrates are not intended for biological applications. Chapter 3 investigated the ability of a novel two-dimensional (2D) tungsten (W) and silicon oxide (SiO2) micron and sub-micron scale patterned substrates to influence the alignment behavior of cells under different experimental conditions of (1) symmetry of the substrates comb structures, (2) cell type, (3) incubation time, and (4) serum-content in the culture media. Results from the pattern-dependent cell behavior indicate that adherent cells on 10 μm line widths symmetric comb structures (equal W and SiO2 parallel lines) exhibited the highest alignment performance; on which, ~54±3 % of Vero cells and ~70±4 % of prostate cancer (PC3) cells, respectively, oriented themselves within ±10° parallel to the W lines y-axis. A time-course study to understand the pattern-dependent cell behavior indicated that after ~36 hours of incubation, cells reached a peak alignment rate of ~67±7 %. Additionally, a culture media-dependent Vero cells alignment on 10 μm line widths symmetric comb structures was conducted. Three different culture media were used, the baseline medium with fetal bovine serum (FBS), serum-free medium (SFM), and SFM supplemented with FBS. Results indicate that ~85±1 %, ~40±6 % and ~76±4 % of cells oriented themselves within ±10° parallel to the W lines y-axis, respectively. Results indicate that the alignment behavior of cells on symmetric comb structures is; (1) W line widths dependent, (2) incubation time-dependent, and (3) serum-dependent. Cells on 10 μm W lines width symmetric comb structures exhibited the highest alignment performance within ±10˚ parallel to the W lines y-axes. However, on asymmetric comb structures with unequal width of parallel W and SiO2 lines, results indicate that the alignment of Vero cells is SiO2 line width-dependent, rather than W line widths. A mathematical model was developed to understand and predict the geometry-dependent cell behavior on both symmetric and asymmetric comb structures. Results indicate that experimental and modeled are consistent. Furthermore, the effect of antimycin A, a bacterial toxin in the culture media on the alignment behavior of human dermal fibroblast (GM5565) cells was investigated on the same 2D W/SiO2 substrates. Results revealed that ~68±2 %, and ~37±5 % of GM5565 cells oriented themselves within ±20° parallel to the W lines y-axis, with and without the presence of antimycin A in the culture media, respectively. Findings demonstrate the adverse effect of antimycin A in the culture media on the alignment behavior of cells. Chapter 4 investigated the effect of single-species protein (human and bovine serum albumin (HSA, and BSA), fibronectin (FN), vitronectin (VN), and collagen (Col-IV)) and FBS on the alignment behavior of mammalian Vero cells. Two experimental pathways are conducted in which single species proteins or FBS is used as (a) supplement for SFM, and (b) pre-adsorbed on the substrates prior to seeding the cells. Results indicate that protein as a supplement for the SFM, rather than pre-adsorbed, induced higher cell alignment. Chapter 5 investigated the effect of a novel three-dimensional (3D) substrate of tantalum (Ta) trenches and SiO2 (lines) fabricated to mimic the in vivo effect of ECM in inducing a preferential cell alignment. The results of pattern-dependent cell alignment indicate that ~91±3 % of cells on 10 μm trench’s width comb structure, oriented themselves within ±10° parallel to the Ta trenches’ y-axis. This was hypnotized by higher selective adhesion to Ta (trenches’ sidewalls and bottom included) rather than SiO2. Chapter 6 investigated the effect of a novel 3D monolithic substrate of Ta lines and trenches on the alignment behavior of Vero cells as a function of topography. The substrate was developed to isolate the effect of materials (Ta) from the 3D Ta/SiO2 substrate developed and investigated in Chapter 5. Results indicate that ~72±9 % of cells on the 10 μm trench width Ta comb structure, oriented themselves within ±10° parallel to the Ta trenches’ y-axis. The decrease in cell alignment on the 3D Ta monolithic substrate in comparison to the 3D Ta/SiO2 substrate is regarded to the Ta effect on cell alignment

Design of self-repairable superhydrophobic and switchable surfaces using colloidal particles

The design of functional materials with complex properties is very important for different applications, such as coatings, microelectronics, biotechnologies and medicine. It is also crucial that such kinds of materials have a long service lifetime. Unfortunately, cracks or other types of damages may occur during everyday use and some parts of the material should be changed for the regeneration of the initial properties. One of the approaches to avoid the replacement is utilization of self-healing materials. The aim of this thesis was to design a self-repairable material with superhydrophobic and switchable properties using colloidal particles. Specific goals were the synthesis of colloidal particles and the preparation of functional surfaces incorporated with the obtained particles, which would exhibit a repairable switching behavior and repairable superhydrophobicity. In order to achieve these goals, first, methods of preparation of simple and functional colloidal particles were developed. Second, the behavior of particles at surfaces of easy fusible solid materials, namely, paraffin wax or perfluorodecane, was investigated

Mechano-Electrochemical Interactions and Stochastics in Intercalation Electrodes

Lithium ion battery (LIB) is replacing all the other battery chemistries from the portable electronic and automotive market due to its superior energy and power density. During operation, transport of lithium atoms within the active particles through diffusion process induces large amount of diffusion induced stress (DIS). A computational methodology has been developed that is capable of estimating the concentration gradient, subsequent DIS and formation of microcracks within graphite active particles. Nucleation of these microcracks form large spanning cracks, which not only impedes the transport of lithium within the solid phase but also acts as fresh sites for the formation of solid electrolyte interface (SEI). Active particles of smaller size (<5μm) and operation at lower rates experiences negligible capacity fade due to microcrack formation. Damage evolution in brittle media occurs initially in a random fashion and towards the end localized propagation is observed. Grain/grain-boundary microstructures with smaller grain sizes display higher strength against crack propagation. By solving the dynamic momentum balance equation, the acoustic emission spectra and jump in energy release rate (avalanche), observed in experiments can be predicted. Since only brittle crack propagation is being considered, evolution of mechanical damage happens in the first three cycles, and then saturates. A reduced order model (ROM) has been developed that can predict the amount of mechanical degradation as a function of particle size and rate of operation. A pseudo 2D computational methodology has been demonstrated that can predict the increase in mass transport resistance and performance decay in lithium ion batteries due to mechanical degradation. Under drive cycle operation, it is safe to use anode particles of radius smaller than 10μm from the capacity fade perspective. Transport of lithium inside high capacity anode materials (such as, Si, Sn) occurs through two phase diffusion process. This gives rise to DIS and fracture at the two phase interface and the particle surface due to high volume expansion. Usage of functionally graded Si with reduced elastic modulus close to the surface is capable of minimizing the microcrack formation. Creep deformation can be significant in Sn active particles during operation at low rates

APPLICATIONS OF INNOVATIVE BUILDING MATERIAL AND COMPUTER VISION METHODS IN GEOTECHNICAL ENGINEERING

Ph.D

Tracing back the source of contamination

From the time a contaminant is detected in an observation well, the question of where and when the contaminant was introduced in the aquifer needs an answer. Many techniques have been proposed to answer this question, but virtually all of them assume that the aquifer and its dynamics are perfectly known. This work discusses a new approach for the simultaneous identification of the contaminant source location and the spatial variability of hydraulic conductivity in an aquifer which has been validated on synthetic and laboratory experiments and which is in the process of being validated on a real aquifer

Multimodal Imaging for Characterisation and Testing of Composite Materials

Carbon fibre reinforced polymers (CFRP) are widely used across several industries, including aerospace, as they are lightweight and offer superior mechanical properties. Barely Visible Impact Damage (BVID), including cracks, delaminations, fibre debonding, as well as manufacturing defects such as porosity, are detrimental to CFRP structural integrity and detection of such faults is important. Different non-destructive evaluation (NDE) methods exist, including ultrasound, X-ray computed tomography (X-ray CT), infrared, and liquid penetrant testing. Edge Illumination X-ray Phase Contrast imaging (EI XPCi) was benchmarked as a viable NDE method for damage detection in CFRP, as it offers additional information through multimodal imaging. With the acquisition of at least three images, EI XPCi allows for the retrieval of the attenuation, differential phase, and dark field signals, using a pair of apertured masks. EI XPCi CT was compared with ultrasonic immersion C-scan imaging and high-resolution X-ray CT for the detection of severe impact damage in a composite plate (visible indent damage on surface of plate and protrusion on the back). The full extent and scale of the different defects were observed in the phase-based signals to a better standard than ultrasonic immersion imaging, with observations confirmed using high resolution X-ray CT. Planar EI XPCi was then compared to contrast agent X-ray imaging and ultrasonic immersion C-scan imaging on a different, less damaged specimen (only small crack visible on surface), showing that planar EI XPCi can detect a network of cracks across the specimen and overcame some of the limitations of contrast agent X-ray imaging. However, in the planar imaging, delamination damage was only detected by the ultrasonic measurement, showing the necessity of using both ultrasonic imaging and EI XPCi for a complete understanding of the damage in the plate. EI XPCi was used for the quantification of porosity for woven composite plates with varying porosity (0.7% to 10.7%), compared to ultrasonic through transmission imaging and destructive matrix digestion. The introduction of the standard deviation of the differential phase (STDP) showed excellent correlation with the porosity calculated from matrix digestion. The STDP signal quantifies the variation of the distribution of inhomogeneities for features of a scale equal to or above the system resolution (in this case, 12µm along the direction of phase sensitivity), which was advantageous for the investigated set of specimens with larger porosity

Computational Heat Transfer and Fluid Mechanics

With the advances in high-speed computer technology, complex heat transfer and fluid flow problems can be solved computationally with high accuracy. Computational modeling techniques have found a wide range of applications in diverse fields of mechanical, aerospace, energy, environmental engineering, as well as numerous industrial systems. Computational modeling has also been used extensively for performance optimization of a variety of engineering designs. The purpose of this book is to present recent advances, as well as up-to-date progress in all areas of innovative computational heat transfer and fluid mechanics, including both fundamental and practical applications. The scope of the present book includes single and multiphase flows, laminar and turbulent flows, heat and mass transfer, energy storage, heat exchangers, respiratory flows and heat transfer, biomedical applications, porous media, and optimization. In addition, this book provides guidelines for engineers and researchers in computational modeling and simulations in fluid mechanics and heat transfer

The role of chemistry and strut porosity and the influence of serum proteins in modulating cellular response to bone graft substitutes

The objective of this thesis was to investigate the role of hydroxyapatite and silicate-substituted hydroxyapatite synthetic bone graft substitute (SBG) material properties in modulating the processes of protein adsorption and desorption, and their combined role in the subsequent regulation of cell attachment, proliferation and differentiation on the surfaces of these materials in vitro. As a result of their purported role in promoting osteogenic behaviour in vivo the materials parameters selected for investigation were chemistry (stoichiometric hydroxyapatite (HA) versus 0.8wt% silicate-substituted hydroxyapatite (SA)) and strut porosity (20% versus 30% strut porosity). Cell attachment and response to different SBG was assessed to samples in the ‘as received’ condition as well as after a series of sequentially varied pre-treatments with solutions of phosphate buffered saline or cell culture media either unsupplemented or in combination with mixed serum proteins and/or Fibronectin (Fn). This enabled investigation of the effect of sample chemistry and strut porosity on mixed serum protein interactions and Fn adsorption under both competitive and non-competitive conditions, and the study of subsequent regulation of cell attachment and response as a consequence of pre-treatment. Results showed that serum protein interactions were key to modulation of cell response to chemistry, and there was evidence that for Fn this may be related to conformational changes in the adsorbed protein rather than its level of enrichment in the protein interlayer. In terms of the materials properties investigated strut porosity was found to be the most dominant factor in the regulation of cell response, where SBG with 30% strut porosity promoted human mesenchymal stem cell (hMSC) osteoblastic differentiation. Moreover hMSC response to SBG with 30% strut porosity seemed to be less sensitive to pre-treatment. In conclusion, the results of these experiments indicate that strut porosity more directly influences the cellular response to HA and SA BGS than chemistry in vitro. Moreover, the role that Fn and other serum proteins have in regulating this response is dependent on the physiological environment and BG

Nanoscale Electric Phenomena at Oxide Surfaces and Interfaces by Scanning Probe Microscopy

Scanning Probe Microscopy is used to study and quantify the nanoscale electric phenomena in the two classes of oxide systems, namely transport at electroactive grain boundaries and surface behavior of ferroelectric materials. Scanning Impedance Microscopy is developed to study the capacitance and local C-V characteristic of the interfaces combining the spatial resolution of traditional SPMs with the precision of conventional electrical measurements. SPM of SrTiO3 grain boundaries in conjunction with variable temperature impedance spectroscopy and I-V measurements allowed to find and theoretically justify the effect of field suppression of dielectric constant in the vicinity of the electroactive interfaces in strontium titanate. Similar approaches were used to study ferroelectric properties and ac and dc transport behavior in a number of polycrystalline oxides. In the second part, the effects of local charge density on the chemistry and physics of ferroelectric surfaces are studied. The kinetics and thermodynamics parameters of adsorption are assessed by variable temperature SPM. Piezoresponse force microscopy is used to engineer domain patterns on ferroelectric surfaces. Localized photochemical activity of ferroelectric surfaces is explored as a new tool for metallic nanostructures fabrication.Comment: Ph.D. Thesis, September 2002, 304 pages, 108 figures, 2.4 MB PDF file, Higher quality version available at sergei2.kalininweb.co