Grating based X-ray phase contrast imaging sets out to overcome the limits of conventional X-ray imaging in the detection of subtle density differences and opens a way to characterize a sample's microstructure without the need for ultrahigh spatial resolution. The technique relies on grating structures with micrometric periods and extreme aspect ratio - their fabrication by X-ray lithography with optimal structure quality is the topic of this work.
Grating based X-ray phase contrast imaging sets out to overcome the limits of conventional X-ray imaging in the detection of subtle density differences and opens a way to characterize a sample's microstructure without the need for ultrahigh spatial resolution. The technique relies on grating structures with micrometric periods and extreme aspect ratio - their fabrication by X-ray lithography with optimal structure quality is the topic of this work. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.
This thesis presents research on novel X-ray imaging methods that improve the study of specimens with small density differences, revealing their inner structure and density distribution. Exploiting the phase shift of X-rays in a material can significantly increase the image contrast compared to conventional absorption imaging. This thesis provides a practical guide to X-ray phase-contrast imaging with a strong focus on X-ray speckle-based imaging, the most recently developed phase-sensitive method. X-ray speckle-based imaging only requires a piece of abrasive paper in addition to the standard X-ray imaging setup. Its simplicity and robustness combined with the compatibility with laboratory X-ray sources, make it an ideal candidate for wide user uptake in a range of fields. An in-depth overview of the state of the art of X-ray speckle-based imaging and its latest developments is given in this thesis. It, furthermore, explores a broad range of applications, from X-ray optics characterisation, to biomedical imaging for 3D virtual histology and geological studies of volcanic rocks, demonstrating is promising potential. Moreover, the speckle-based technique is placed in the context of other phase-sensitive X-ray imaging methods to assist in the choice of a suitable method, hence serving as a guide and reference work for future users.
The advantages offered by the flexible electronics and control systems technologies were utilized for tackling the challenges facing two crucial Magnetic Resonance (MR) applications. The first application is in the field of interventional Magnetic Resonance Imaging (MRI), and the other application is in the field of Nuclear Magnetic Resonance spectroscopy (NMR).
This work deals with the process of photon upconversion in surface-anchored metal-organic frameworks. During the upconversion, two low-energy photons are absorbed and fused into a higher-energy photon, which is emitted. In this work, this process is analyzed in surface-bound metal-organic frameworks by spectroscopic methods. Furthermore, the application for increasing the efficiency of solar cells is discussed.
Elastocaloric cooling is an emerging solid-state cooling technology with the potential to provide environmentally friendly, efficient cooling. The elastocaloric effect in superelastic shape memory alloy films is used to develop advanced cooling devices for small-scale applications. Cascaded and parallelized devices are developed to increase device temperature span and cooling capacity. The concepts are proven experimentally, a maximum temperature span of 27° C is achieved in a cascaded device.
Die Forschung im Bereich der Mikro-Energiegewinnungssysteme wurde durch den Bedarf an autarken, stabilen Energiequellen für vernetzte drahtlose Sensoren vorangetrieben. Abwärme, insbesondere bei Temperaturen unter 200 °C, stellt eine vielversprechende, aber mit den derzeitigen Umwandlungstechnologien schwer zu gewinnende Energiequelle dar. - Research into micro energy harvesting systems has been driven by the need for self-sustaining, stable power sources for interconnected wireless sensors. Waste heat, particularly at temperatures below 200 °C, presents a promising but challenging energy source to recover using current conversion technology.
Hybrid perovskite photovoltaics could play a vital role in future’s renewable energy production. However, there are still severe challenges when scaling the technology. In this work, perovskite solution films drying in laminar and slot-jet air flows are investigated extensively by optical in situ characterization. The main results are a quantitative model of perovskite drying dynamics and a novel in situ imaging technique – yielding valuable predictions for large-scale perovskite fabrication.
This work offers three solutions tailored to specific applications to overcome NMR challenges in the micro-domain. As the first sub-topic of this work, different potential electrode designs, compatible with NMR technique, are suggested and experimentally evaluated. As the second focus point, this work tackles multinuclear detection challenges. In parallel, a low-cost, broadband insert is discussed to enhance the sensitivity of standard NMR coils when a small sample volume is available.
Inspired by superhydrophobic leaves of water plants, a flexible superhydrophobic self-cleaning, transparent thin polymeric nanofur film was fabricated through highly scalable hot embossing and hot pulling techniques. Nanofur can retain an air film underwater, whose stability against external stimuli such as high pressure and movement through fluids is investigated. Additionally, the optical properties of nanofur are investigated and exploited to enhance the efficiency of optoelectronic devices.
