Acoustic filters for signal filtering are used in wireless technologies operating at gigahertz frequencies for communication systems such as next generation cell phones. Multilayered porous silicon structures have been fabricated from silicon wafers to create the Bragg mirror section of a bulk acoustic wave filter. These porous silicon multilayers have been designed for use from 500 MHz – 20 GHz with primary focus on frequencies at 1 GHz. The porous silicon multilayers consist of alternating layers of high and low acoustic impedance layers on a bulk silicon substrate. They are fabricated using electrochemical etching where the current density during the etch determines the porosity and hence acoustic impedance of each layer. Bragg mirrors, FabryPerot filters, microcavities and rugate filters can be produced in this way due to the control of the tuneable porosity profile throughout the structure. The porosity of the layer modifies the elastic constants of the layer such as the Young’s modulus and hence the velocity of the bulk acoustic waves travelling through it. The behaviour of bulk acoustic waves through silicon is known but in order to fabricate porous silicon acoustic filters, the dependence of the longitudinal wave velocity as a function of porosity must also be known. This has been studied using acoustic transmission measurements on single porous silicon layers and then extended to multilayered structures. Rugate filters are single frequency filters that have not previously been studied for acoustic applications. In this study the first acoustic rugate filters have been fabricated using porous silicon material that exhibit only one stopband near 1 GHz. Bragg mirrors have been made with acoustic transmission measurements showing the locations of the stopbands. Porous silicon microcavities have also been fabricated along with filters that have apodisation functions. This work could form the basis of future efforts to produce and incorporate allSi multilayers into acoustic filters that are easily fabricated at a high level of quality and reliability that will serve to be efficient and cost effective.

Usability of many chemical substances with significant potential for biomedical applications is limited by their poor solubility in water or limited stability in the physiological environment. One of promising strategies for therapeutic targeted delivery of these types of substances into cells and tissues is their encapsulation inside polyelectrolyte microcapsules (Volodkin et al., 2004b, Sukhorukov et al., 1998b). Successful internalisation of microcapsules loaded with various macromolecules have been observed in several types of living cells (Javier et al., 2008, Kastl et al., 2013), however the mechanisms of the uptake of capsules by living cells are not yet fully understood. Detailed understanding of physico-chemical and mechanical interactions between capsules and living cells is required for specific targeting, effective delivery, and elimination of any potential toxic side effects. This has been largely limited by capabilities of available imaging techniques and lack of specific fluorescent markers for certain types of cellular uptake. The rate of internalisation of microcapsules was primarily studied at the level of cell population using conventional optical/fluorescence microscopy, confocal microscopy, and flow cytometry (Gao et al., 2016, Ai et al., 2005, Sun et al., 2015). These conventional fluorescence methods are known to be prone to overestimating the number of internalised capsules due to their limited capability to exclude capsules which were not fully internalised and remained attached to the cell surface (Javier et al., 2006). Experimental evidence with resolution high enough to resolve the fine membrane processes interacting with microcapsules has been limited to fixed samples imaged by scanning electron microscopy and transmission electron microscopy (Kastl et al., 2013) capturing randomly timed "snapshots" of what is likely to be highly dynamic and complex interaction. Physical force interactions between cellular membrane and capsules during the internalisation were suggested to cause buckling of capsules based on indirect evidence obtained using fluorescence microscopy in live cells 15 (Palankar et al., 2013) and separate measurements of capsule deformation under colloidal probe atomic force microscopy (AFM) outside of the cellular environment (Delcea et al., 2010, Dubreuil et al., 2003). However, our knowledge of the mechanical properties of the fine membrane structures directly involved in the internalisation process or how these structures form during the internalisation is very limited, if non-existent. Here we employ a different approach based on a high-resolution scanning probe technique called scanning ion conductance microscopy (SICM). SICM uses reduction in ionic current through the probe represented by an electrolyte-filled glass nanopipette immersed in saline solution to detect proximity of sample surface (Hansma et al., 1989, Korchev et al., 1997a). The technique has been previously used for high-resolution scanning of biological samples of complexity similar to what can be expected in case of microcapsules interacting with cells (Novak et al., 2014, Novak et al., 2009), and also for mapping mechanical properties at high resolution (Ossola et al., 2015, Rheinlaender and Schaffer, 2013). It has been proved to be able to visualise internalisation process of 200 nm carboxy-modified latex nanoparticles (Novak et al., 2014), however it is not clear whether it would be suitable for visualising internalisation of substantially larger, microscale-sized particles. The aim of this research was to visualize the live internalisation process of microcapsules entering cells by using SICM. The first two chapters of this thesis are introduction and literature review, which summarise the current state of the art. Chapter 3 states the aim and objectives of this study. Chapter 4 introduces the materials and methods we used in our research. Chapter 5, 6, 7 present the main findings of our research. Chapter 5 states the challenges we met in visualising the live internalisation of microcapsule as well as our solution for overcoming those challenges. At the end of that chapter, we describe the detailed procedure we used for recording the live internalisation of microcapsules. The results we got using this procedure are presented in chapter 6 and 7. In chapter 8, we discuss the results we found by comparing them to the results of previous research. In chapter 9, we summarise our study and give some suggestions on future work.

<p>This thesis concerns the growth and magnetic properties of thin films and multilayers. The samples were grown by magnetron sputtering, and characterized structurally mainly by x-ray diffraction and reflectivity. The magnetic characterization of the multilayers was done by magneto-optical Kerr technique, SQUID magnetometry and, in two samples, by neutron reflectometry.</p><p>Arrays of small elements of polycrystalline permalloy (FeNi alloy with 19 wt% Fe) are of interest as a component in non-volatile magnetic random access memories (MRAM). Here the shape dependence of the domain structure in such elements was studied by magnetic force microscopy (MFM) and in thin ring magnets the 'onion' state could be seen for the first time. Also, by post-annealing in hydrogen atmosphere the number of domains decreased in each element due to enhanced relaxation and defect reduction.</p><p>Furthermore, permalloy-based anisotropic magnetoresistance (AMR) in read heads are nowadays replaced by material combinations that have a giant magnetoresistance (GMR) effect. In this work Fe/V(001) and Fe_0.82Ni_0.18/V(001) superlattices, i.e. single-crystal-like multilayers, were investigated. These systems showed much smaller GMR effect compared to the Fe/Cr system. However, by introducing Ni into the Fe layers the magnetic anisotropy and the interlayer exchange coupling (IEC) decreased, thereby increasing the sensitivity, which is a key property for a magnetic sensor. The interface region showed a reduced magnetic moment, and the influence of the structural quality was modelled and investigated theoretically in the Fe_0.82Ni_0.18/V case. Also, in the Fe(2-3 ML)/V(x ML) superlattices (ML=monolayers) the transition temperature from long-range magnetic order to paramagnetic order oscillated with the V layer thickness (x) as a result of the oscillatory behaviour of the IEC.</p><p>The introduction of hydrogen in the non-magnetic layers of, for example, Fe/V(001) superlattices is a way to tune the IEC strength. Here the tuning was used as a tool to study the magnetic order in a low-dimensional magnet. At the critical hydrogen concentration <H/V>=0.022 the Fe layers in an Fe(2 ML)/V(13 ML) superlattice became decoupled. Then the system behaved as a two-dimensional Ising magnet with a finite ordering temperature of about 60 K.</p>

We had previously shown that regularization principles lead to approximation schemes, as Radial Basis Functions, which are equivalent to networks with one layer of hidden units, called Regularization Networks. In this paper we show that regularization networks encompass a much broader range of approximation schemes, including many of the popular general additive models, Breiman's hinge functions and some forms of Projection Pursuit Regression. In the probabilistic interpretation of regularization, the different classes of basis functions correspond to different classes of prior probabilities on the approximating function spaces, and therefore to different types of smoothness assumptions. In the final part of the paper, we also show a relation between activation functions of the Gaussian and sigmoidal type.

This thesis concerns the growth and magnetic properties of thin films and multilayers. The samples were grown by magnetron sputtering, and characterized structurally mainly by x-ray diffraction and reflectivity. The magnetic characterization of the multilayers was done by magneto-optical Kerr technique, SQUID magnetometry and, in two samples, by neutron reflectometry. Arrays of small elements of polycrystalline permalloy (FeNi alloy with 19 wt% Fe) are of interest as a component in non-volatile magnetic random access memories (MRAM). Here the shape dependence of the domain structure in such elements was studied by magnetic force microscopy (MFM) and in thin ring magnets the 'onion' state could be seen for the first time. Also, by post-annealing in hydrogen atmosphere the number of domains decreased in each element due to enhanced relaxation and defect reduction. Furthermore, permalloy-based anisotropic magnetoresistance (AMR) in read heads are nowadays replaced by material combinations that have a giant magnetoresistance (GMR) effect. In this work Fe/V(001) and Fe0.82Ni0.18/V(001) superlattices, i.e. single-crystal-like multilayers, were investigated. These systems showed much smaller GMR effect compared to the Fe/Cr system. However, by introducing Ni into the Fe layers the magnetic anisotropy and the interlayer exchange coupling (IEC) decreased, thereby increasing the sensitivity, which is a key property for a magnetic sensor. The interface region showed a reduced magnetic moment, and the influence of the structural quality was modelled and investigated theoretically in the Fe0.82Ni0.18/V case. Also, in the Fe(2-3 ML)/V(x ML) superlattices (ML=monolayers) the transition temperature from long-range magnetic order to paramagnetic order oscillated with the V layer thickness (x) as a result of the oscillatory behaviour of the IEC. The introduction of hydrogen in the non-magnetic layers of, for example, Fe/V(001) superlattices is a way to tune the IEC strength. Here the tuning was used as a tool to study the magnetic order in a low-dimensional magnet. At the critical hydrogen concentration &lt;H/V&gt;=0.022 the Fe layers in an Fe(2 ML)/V(13 ML) superlattice became decoupled. Then the system behaved as a two-dimensional Ising magnet with a finite ordering temperature of about 60 K.

BMGs (bulk metallic glasses) exhibit many exceptional advantages for engineering applications, such as high strength, good corrosion resistance, etc. Despite of having these excellent properties, the brittle nature of metallic glasses in the bulk and thin film forms inevitably imposes limitation and restricts the wide application of BMGs and TFMGs. Composite concept might be another idea to solve this dilemma. In order to manufacture the bulk metallic glass composites (BMGCs), the approaches are classified into two categories: the intrinsic and extrinsic methods. For the intrinsic method, the in situ process and heat treatment process are two kinds of ways in common uses. Adding reinforcements into the BMGs or TFMGs is extensively used to manufacture composites in the extrinsic method. In this study, the deformation behaviors of multilayer (amorphous/nanocrystalline) micropillars are studied by uniaxial microcompression tests at room temperature. The nanocrystalline layer to be coupled with the amorphous layer can be of either face-centered cubic (FCC), hexagonal close-packed (HCP) or body-centered cubic (BCC) in crystal structure. The current study demonstrates that brittle problem of a metallic glass coating can be alleviated by percolating with a nanocrystalline metallic underlayer. The brittle thin film metallic glass can become highly ductile and exhibit a plastic strain over 50% at room temperature. The present study has an important implication for MEMS applications, namely, the life span of a brittle amorphous layer can be significantly improved by using an appropriate metallic underlayer. The brittle problem of thin film ZrCu metallic glasses was also treated by invoking soft Cu layers with optimum film layer thickness. Such multilayered amorphous/crystalline samples exhibit superplastic-like homogeneous deformation at room temperature. It is found that the deformability of the resultant micropillars depends on the thickness of Cu layers. Microstructural observations and theoretical analysis suggest that the superplastic-like deformation mode is attributed to homogeneous co-deformation of amorphous ZrCu and nanocrystalline Cu layers because the 100 nm-thick Cu layers can provide compatible flow stress and ¡§plastic zone¡¨ size well matched with those of ZrCu amorphous layers. Besides, we also made attempts to investigate the critical sample size below which shear band localization would disappear and the sample can deform homogeneously. In situ TEM compression was conducted on amorphous ZrCu nanopillars to study shear band formation behavior. The nanopillar is 140 nm in diameter and with a taper angle of 3¢X. Experimental observations and simulations based on a free-volume model both demonstrate that the deformation was localized near the top of the tapered metallic glass pillar. Eventually, the interface nature of metallic glass amorphous/crystalline was characterized through evaluating its energy and validated by the mechanical response of micropillar with ~45o inclined interface under compression. The calculated results showed that the ZrCu/Zr interface energy resides several joules per meter square, meaning that the Zr/ZrCu interface is inherently strong. The high strong adhesion ability of ZrCu/Zr interface was further confirmed by shear fracture happening rightly within the Zr layers rather than along the interface when compressing the ZrCu/Zr micropillars with 45o inclined interface.

In this thesis, we proposed general forms of eigen-mode analysis for multilayer optical waveguides. This study discussed the periodic structure in transverse direction and used the slowly varying envelope approximation to approximate the wave function. Firstly, we presented a general method for analyzing the multilayer nonlinear optical waveguide structure by using modal theory. The nonlinear optical waveguide is a medium whose refractive index changes with the electric field intensity. The general method can also be degenerated into some other special cases for analyzing multilayer nonlinear optical waveguide. Secondly, a general method for analyzing the multilayer optical waveguides with photonic metamaterials characterized by simultaneously negative dielectric permittivity and magnetic permeability was studied. The research pointed out explicitly that the three-layer planar waveguide with photonic metamaterials could support forbidden regions. The complete set of modes of all possible solutions for the TE wave in photonic metamaterials optical waveguide was found. The transverse electric field distributions and dispersion relations in multilayer optical waveguides can be obtained by using these general forms. Finally, we used the general forms to design an all-optical mode converter which composed of a pair of multibranch optical waveguides. The analytical and numerical results show excellent agreement.

This study focuses on the design, fabrication, test and application of in-plane rotary electromagnetic micro-generator to obtain a high power output. The micro-generator comprises multilayer planar low temperature co-fired ceramics (LTCC) Ag micro-coil and multipole hard magnet of Nd/Fe/B. Finite element simulations have been carried out to observe electromagnetic information. The study also establishes analytical solutions for the micro-generator to predict the induced voltage. Three different configurations of planar micro-coils investigated, which are sector-shaped, circle-shaped, and square-shaped micro-coils. A prototype of the micro-generator is as small as 9¡Ñ9¡Ñ1 mm3 in volume size. The experimental results show that the micro-generator with sector-shaped micro-coil has the highest power output of 1.89 mW, and the effective value of the induced voltage of 205.7 mV at 13,325 rpm is achieved. In application, this study designed and fabricated a planar rotary electromagnetic energy harvester with a low rotary speed for use in bicycle dynamos. Finite element analysis and the Taguchi method were used to design this dynamo system. LTCC technology was applied to fabricate Ag planar multilayer coils with 20 layers. A 28-pole magnet Nd/Fe/B with an outer diameter of 50 mm and a thickness of 2 mm was also sintered and magnetized. This harvester system was approximately 50¡Ñ50¡Ñ3 mm3 in volume. The experimentally induced voltages for 20-layer coils were 1.539 V at the rotary speeds of 300 rpm. The power output was 0.788 mW with an external resistance load of 740 £[, and the efficiency was 26.62%. This harvester is capable of powering a minimum of 200 light emitted diodes (LEDs) (forward voltage (VF) <2.2 V and 20 mA) using a rotary speed of 250 rpm, and can be used for bicycle dynamo lighting.

In this thesis, a standard flow path is proposed to establish the model library for inductors and capacitors in multilayer substrate structure. By the way of excellent agreement between simulation and measurement within self resonant frequency ¡]SRF¡^, we aimed at the demanded performance of passives in modules and adopted Pi-section equivalent circuits as basic model. Meanwhile, an automatic program on CAD-based platform is used for extraction of Pi-model circuit elements and calculation of SRF, quality ¡]Q¡^factor and modeling errors. In the end, we contributed the methodology to have the best performance of embedded passives design in multilayer substrate structure and established a completed model library for inductors and capacitors embedded in low temperature co-fired ceramic¡]LTCC¡^substrate for the design need in implementation of RF modules.

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