Advancing Particle-Based Magneto-Polymer Composites: Processing, Structure, and Performance Optimisation for Actuation, EMI Suppression, and Energy Transduction

Magneto-polymer composites (MPCs) combine the unique properties of magnetic phases with the versatility of a polymer matrix, bestowing improved structural characteristics over bulk magnetic materials, and expanding applicability to multi-functional applications. Full utilisation of MPCs in multi-functional systems is however limited by the high densities of the magnetic phase, MPC processing induced degradations in the magnetic phase and mechanical property degradations associated with the introduction of the magnetic phase into the polymer. This research endeavours to overcome these limitations by pioneering particle-based MPC solutions in the realms of actuation, electromagnetic interference (EMI) suppression, and energy transduction. The research explores processing-property relationships of MPCs at the atomic, nano, micro and meso levels using a combination of experimental, theoretical and computational approaches. High energy X-ray synchrotron techniques are used to explore the effect of ball mill processing on the crystal structure and magnetic properties of magnetostrictive alloy particulates applicable to sensing and energy transduction. Leveraging these milling techniques, the shape and alignment of magnetostrictive micro-particles within a polymer is controlled, inducing anisotropy and allowing for improved magnetostrictive strains at reduced magnetic phase volumes and overall composite mass. Moreover, the integration of a piezoelectric polymer facilitates magnetoelectric coupling, with particle shaping and alignment demonstrated to enhance sensing and energy harvesting efficiencies. In addition to these structural and morphological investigations, an innovative epoxy-silane functionalisation regime to enhance particle-polymer coupling is developed and validated. Additionally, a novel actuated dielectric lossy sheet structure is proposed as a light-weight EMI mitigation solution, surpassing conventional absorber methods in achieving a superior balance between bandwidth and EMI suppression performance. The integration of advanced shaping, alignment, and functionalisation strategies in conjunction with actuated structures underscores a transformational opportunity to improve the performance of MPCs. Coupled with foundational insights garnered by exploring the effects of magnetic particle processing on material properties, this research paves an exciting trajectory toward unlocking the future potential of multi-functional MPC applications

Electrically tunable optical metasurfaces

Optical metasurfaces have emerged as a groundbreaking technology in photonics, offering unparalleled control over light–matter interactions at the subwavelength scale with ultrathin surface nanostructures and thereby giving birth to flat optics. While most reported optical metasurfaces are static, featuring well-defined optical responses determined by their compositions and configurations set during fabrication, dynamic optical metasurfaces with reconfigurable functionalities by applying thermal, electrical, or optical stimuli have become increasingly more in demand and moved to the forefront of research and development. Among various types of dynamically controlled metasurfaces, electrically tunable optical metasurfaces have shown great promise due to their fast response time, low power consumption, and compatibility with existing electronic control systems, offering unique possibilities for dynamic tunability of light–matter interactions via electrical modulation. Here we provide a comprehensive overview of the state-of-the-art design methodologies and technologies explored in this rapidly evolving field. Our work delves into the fundamental principles of electrical modulation, various materials and mechanisms enabling tunability, and representative applications for active light-field manipulation, including optical amplitude and phase modulators, tunable polarization optics and wavelength filters, and dynamic wave-shaping optics, including holograms and displays. The review terminates with our perspectives on the future development of electrically triggered optical metasurfaces

NASA Tech Briefs, September 2001

Topics include: special coverage section on sensors, and sections on electronic components systems, software, materials, machinery/automation, manufacturing/fabrication, bio-medical, book and reports, and a special section of Photonics Tech Briefs

Doctor of Philosophy

dissertationThis dissertation describes the advancements made towards the implementation of Tip-Enhanced Fluorescence Microscopy (TEFM) in imaging biological specimens. This specialized type of microscopy combines the chemical specifi city of optical microscopy techniques with the resolution of atomic force microscopy (AFM). When an AFM probe is centered in the focal spot of an excitation laser with axial polarization, the probe concentrates the optical field such that it can be used to induce nanometer scale fluorescence. The physical mechanisms of this optical field enhancement are set forth in detail. The feasibility of this technique for imaging bimolecular networks is discussed in regard to the requirements for adequate image contrast, as well as for obtaining fi eld enhancement in aqueous environments. A semianalytical model for image contrast for TEFM has been developed. This model shows that using demodulation techniques greatly increases the image contrast attainable with this technique, and is capable of predicting the requisite enhancement factors to achieve imaging of biomolecular networks at good contrast levels. This model predicts that signal enhancement factors on the order of 20 are needed to image densely packed samples. This dissertation also highlights a novel tomographical imaging approach. By timestamping the fluorescence photon arrival times, and subsequently correlating them to the timestamped motion of a vertically oscillating probe, a three-dimensional map of tip-sample interactions can be constructed. The culmination of these advancements has led to the ability to map the interactions between single carbon nanotubes and single fluorescent nanocrystals (quantum dots). Various attempts at using TEFM in water have been thus far unsuccessful. Several explanations for this shortfall have been identi ed|understanding these shortcomings has helped to identify the optimal excitation conditions for field enhancement

Antenna Design for 5G and Beyond

With the rapid evolution of the wireless communications, fifth-generation (5G) communication has received much attention from both academia and industry, with many reported efforts and research outputs and significant improvements in different aspects, such as data rate speed and resolution, mobility, latency, etc. In some countries, the commercialization of 5G communication has already started as well as initial research of beyond technologies such as 6G.MIMO technology with multiple antennas is a promising technology to obtain the requirements of 5G/6G communications. It can significantly enhance the system capacity and resist multipath fading, and has become a hot spot in the field of wireless communications. This technology is a key component and probably the most established to truly reach the promised transfer data rates of future communication systems. In MIMO systems, multiple antennas are deployed at both the transmitter and receiver sides. The greater number of antennas can make the system more resistant to intentional jamming and interference. Massive MIMO with an especially high number of antennas can reduce energy consumption by targeting signals to individual users utilizing beamforming.Apart from sub-6 GHz frequency bands, 5G/6G devices are also expected to cover millimeter-wave (mmWave) and terahertz (THz) spectra. However, moving to higher bands will bring new challenges and will certainly require careful consideration of the antenna design for smart devices. Compact antennas arranged as conformal, planar, and linear arrays can be employed at different portions of base stations and user equipment to form phased arrays with high gain and directional radiation beams. The objective of this Special Issue is to cover all aspects of antenna designs used in existing or future wireless communication systems. The aim is to highlight recent advances, current trends, and possible future developments of 5G/6G antennas

Microelectromechanical Systems and Devices

The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators

Antenna Design for 5G and Beyond

This book is a reprint of the Special Issue Antenna Design for 5G and Beyond that was published in Sensors

Advanced theory of optical wave propagation and interferometric sensors for topography measurement

Zugleich: Dissertation, Universität Kassel, 201

Investigating the motility of Dictyostelium discodeum using high frequency ultrasound as a method of manipulation

Cell motility is an essential process in the development of all organisms. The earliest stages of embryonic development involve massive reconfigurations of groups of cells to form the early body structures. Embryos are very complex systems, and therefore to investigate the molecular and cellular basis of development a simpler genetically tractable model system is used. The social amoeba Dictyostelium Discoideum is known to chemotax up a chemical gradient. From previous work, it is clear that cells generate forces in the nN range. This is above the limit of optical tweezers and therefore we are investigating the use of acoustic tweezers instead. In this paper, we present recent progress of the investigation in to the use of acoustic tweezers for the characterisation of cell motility and forces. We will describe the design, modelling and fabrication of several devices. All devices use high frequency (>15MHz) ultrasound to exert a force on the cells to position and/or stall them. Also, each device is designed to be suitable for the life-sciences laboratory where form-factor and sterility is concerned. A transducer (LiNo) operating at 24 MHz excites resonant acoustic modes in a rectangular glass capillary (100um by 2mm). This device is used to alter the directionality of the motile cells inside the fluid filled capillary. A quarter-ring PZT26 transducer operating at 20.5MHz is shown to be useful for manipulating cells using axial acoustic radiation forces. This device is used to exert a force on cells and shown to pull them away from a coverslip. The presented devices show promise for the manipulation of cells in suspension. Currently the forces produced are below that required for adherent cells; the reasons for this are discussed. We also report on other issues that arise when using acoustic waves for manipulating biological samples such as streaming and heating

Active and passive reduction of high order modes in the gravitational wave detector GEO 600

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