A super-twisting observer for atomic-force reconstruction in a probe microscope

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThis paper presents a new methodology employing a super-twisting sliding mode observer to reconstruct un-measureable atomic-forces at nano-Newton precision in a Vertically Oriented Probe Microscope (VOPM). The VOPM senses the deflection of a vertically oriented cantilever, caused by shear-force interaction with a confined water layer above the sample-substrate. The paper describes the development of a model and the subsequent experimental process for computing its parameters. This forms the basis for the design of a super-twisting observer to estimate the unknown shear-forces. The reconstructed force can be decomposed into elastic and viscous components ,which are important in biological research.Engineering and Physical Sciences Research Council (EPSRC

Trapped between two beams – higher order laser mode manipulation for cell rotation

Laser light is an exceptionally powerful tool which has been utilised across all natural sciences and engineering. The very high intensities of extremely controllable light have allowed for a diverse range of studies to be carried out. When the intensities are large enough, the act of redirecting the light can create a force which can be sufficient to move small transparent objects. In biology one application of this phenomenon forms a tool for trapping and handling microscopic cellular samples in a contactless way using two laser beams. Such a laser-based tool is the Optical Stretcher, it was invented for measuring the mechanical properties of single cellular biological samples. The work presented in this thesis built upon the Optical Stretcher and to gain expertise in the field, several different biological samples were tested using it, gaining insights into the impact of particular proteins to cell mechanics. The Optical Stretcher, along with the vast majority of cell trapping experiments utilises a rotationally symmetric laser beam, which allows the cells to be moved and held in place, but their orientation is random and subject to large fluctuations. Controlled orientation of cellular specimen can lead to improved 3D imaging of the sample and is an important field of study. Previous work has shown that it is possible to orient a cell using a specially shaped laser beam, however the experimental setups were not well suited to use in biological labs. Henceforth, this thesis investigated and engineered a Dual Beam Laser Trapping device called the Higher Order Mode Cell Rotator, in short HOMCR, in order to build a powerful all-in-fibre tool for tomographic cell rotation. The major component giving rise to the HOMCR was a polarisation controlling device that alters the state of light by squeezing on the laser fibre and inducing local changes in the polarisation profile of the laser light. By characterising this device, its capability has been shown for the first time to manipulate the two lobe higher order modes travelling in optical fibres, leading to an all-in-fibre dynamic cell rotator which was used successfully to trap and orient individual cells and larger biological samples

Second All-Union Seminar on Hydromechanics and Heat and Mass Exchange in Weightlessness, summaries of reports

Abstracts of reports are given which were presented at the Second All Union Seminar on Hydromechanics and Heat-Mass Transfer in Weightlessness. Topics include: (1) features of crystallization of semiconductor materials under conditions of microacceleration; (2) experimental results of crystallization of solid solutions of CDTE-HGTE under conditions of weightlessness; (3) impurities in crystals cultivated under conditions of weightlessness; and (4) a numerical investigation of the distribution of impurities during guided crystallization of a melt

Modular Instrumentation for Controlling and Monitoring In-Vitro Cultivation Environment and Image-based Functionality Measurements of Human Stem Cells

Artificial animal cell culture was successfully developed by Ross Harrison in 1907. But it was not until the 1940’s and 1950’s that several developments occurred, which expedited the cell culturing in-vitro (C-Vitro) to be a consistent and reproducible technique to study isolated living-cells in a controlled environment. Currently, CVitro is one of the major tools in cellular and molecular biology both in the academia and industry. They are extensively utilised to study the cellular physiology/biochemistry, to screen drugs/therapeutic compounds, to understand the effects of drugs/toxic compounds and also to identify the pathways of carcinogenesis/mutagenesis. It is also used in large scale manufacturing of vaccines and therapeutic proteins. In any experimental setup, it is important that the C-Vitro model should represent the physiological phenomena of interest with reasonable accuracy so that all experimental results are statistically consistent and reproducible. In this direction, sensors and measurement systems play important roles in in-situ detection and/or control/manipulation of cells/tissues/environment. This thesis aimed to develop new technology for tailored cell culturing and integrated measurements. Firstly, design and assembly of a portable Invert-upright microscope interchangeable modular cell culturing platform (iuCMP) was envisioned. In contrast to conventional methods, micro-scaled systems mimic the cells' natural microenvironment more precisely, facilitating accurate and tractable models. The iuCMP integrates modular measurement schemes with a mini culture chamber using biocompatible cell-friendly materials, automated environment-control (temperature and gas concentrations), oxygen sensing and simultaneous functional measurements (electrophysiological and image-based). Time lapse microscopy is very useful in cell biology, but integration of advanced >i>in-vitro/device based biological systems (e.g. lab/organ/body-on-chips, or mini-bioreactors/microfluidic systems) into conventional microscopes can be challenging in several circumstances due to multiple reasons. But in iuCMP the main advantage is, the microscope can be switched either as an inverted or as an upright system and therefore can accommodate virtually any in-vitro device. It can capture images from regions that are otherwise inaccessible by conventional microscopes, for example, cells cultured on physical or biochemical sensor systems. The modular design also allows accommodating more sensor or measurement systems quite freely. We have demonstrated the system for video-based beating analysis of cardiomyocytes, cell orientation analysis on nanocellulose, and simultaneous long-term in-situ microscopy with oxygen and temperature sensing in hypoxia. In an example application, the system was utilised for long-term temperature stressing and simultaneous mechanobiological analysis of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). For this the iuCMP together with a temperature sensor plate (TSP) and a novel non-invasive beating analysis software (CMaN—cardiomyocyte function analysis tool, scripted as a subpart of this thesis), was applied for automated temperature response studies in hiPSC-CM cultures. In-situ temperature sensing is usually challenging with bulky external sensors, but TSPs solved this issue. In the temperature response study, we showed that the relationship between hiPSC-CM beating frequency and temperature is non-linear and measured the Q10 temperature coefficients. Moreover, we observed the hiPSC-CM contractile networking, including propagation of the action potential signal between dissociated clusters and their non-invasive measurements. It was the first case where these events were reported in hiPSC-CM clusters and their noninvasive measurements by image processing. The software CMaN comes with a user-friendly interface and, is equipped with features for batch processing, movement centre detection and cluster finding. It can extract six different signals of the contractile motion of cardiomyocytes (clusters or single cells) per processing. This ensures a minimum of one useful beating signal even in the cases of complex beating videos. On the processing end, compared to similar tools, CMaN is faster, more sensitive, and computationally less expensive and allows ROI based processing. In the case of healthy cells, the waveform of the signal from the CMaN resembles an ECG signal with positive and negative segments, allowing the computation of contraction and relaxation features separately. In addition to iuCMP, a Modular optical pH measurement system (MO-pH) for 24/7 non-contact cell culture measurements was also developed. The MO-pH incorporates modular sterilisable optical parts and is used in phenol-red medium cell cultures. The modular assembly of MO-pH cassettes is unique and reusable. Measurements are carried out in a closed flow system without wasting any culture medium and requires no special manual attention or recalibrations during culture. Furthermore, a new absorption correction model was put forward that minimised errors caused e.g. by biolayers in spectrometric pH measurement, which improved the pH measurement accuracy. MO-pH has been applied in long-term human adipose stem cells (hASC) expansion cultures in CO2 dependent and independent media. Additionally, the MO-pH was also utilised to comprehend the behaviour of pH, temperature and humidity in water jacked incubators as well as to record the pH response as a function of temperature in the presence and absence of CO2 in the context of stem cell cultures. The resulting plots clearly showed the interplay between measured parameters indicating a few stress sources present all through the culture. Additionally, it provided an overall picture of behaviour of critical control parameters in an incubator and pointed out the need for bioprocess systems with automatic process monitoring and smart control for maximum yield, optimal growth and maintenance of the cells. Besides, we also integrated MO-pH into flasks with reclosable lids (RL-F) and tested its applicability in stem cell cultures. A standalone system around an RL-F flask was built by combining the cell culture, medium perfusion and optical measurements. The developed RL-F system has been successfully tested in ASC-differentiation cultures. Finally, a few trial experiments for image-based pH estimation aimed for iuCMP have also been carried out. This includes tests with LCD illumination, optical projection tomography, and webcam systems. In reality, the pH is not distributed uniformly in tissues, and has shown a gradient of up to 1.0 pH unit within 1 cm distance. Therefore, producing reliable pH maps also in in-vitro can be important in understanding various common pathologies and location of lesions. A reliable and adequately developed long-term pH mapping method will be an important addition into the iuCMP

Thermal protection properties of aerogel-coated Kevlar woven fabrics

This paper investigated the thermal properties of aerogel-coated Kevlar fabrics under both the ambient temperature and high temperature with laser radiation. It is found that the aerogels combined with a Kevlar fabric contribute to a higher thermal insulation value. Under laser radiation with high temperature, the aerogel content plays a vital role on the surface temperature of the fabrics. At laser radiations with pixel time 330 μs, the surface temperatures of the aerogel coated Kevlar fabrics are 400-440°C lower than that of the uncoated fabric. Results also show that the fabric temperature is directly proportional to pixel time. It can be concluded that the Kevlar fabrics coated with silica aerogel provides better thermal protection under high temperature

Computational Microscopy at 5 Meters Using Symmetric Fourier Sampling

Robotic planetary exploration relies upon a suite of scientific instruments to measure and record the environment under study, with the most ubiquitous instrument being some form of imager. This work describes the development of a microscope that can be mounted to the mast of planetary rover and obtain images with 10 μm spatial resolution at an unprecedented 5 meter distance. Rather than using traditional optics to generate images on a 2D focal plane array, this “remote microscope” uses a computation imaging technique to reconstruct images of targets. A set of four electronically programmable, frequency-shifted collimated laser beams that are symmetric about the axis of the optical system are projected to overlap at a distance of 5 meters and generate moving interference fringes which are used to probe the matched spatial Fourier components of the 2D intensity reflectivity function of the target surface. By probing and collecting a large set of these Fourier measurements, an image of the target is reconstructed using Fourier synthesis. This document provides a detailed description of the optical designs, electronic control requirements, opto-mechanical structures, operational conditions and algorithmic techniques used to generate a functioning computational remote microscope.I describe and analyze a novel optical design capable of achieving the operational requirements of the system and derive the optical parameters and relevant aberrations. A novel optical surface testing technique useful for high departure aspheres is derived and demonstrated with experimental measurements. I describe in detail the optical procedures and electronics components of the laboratory implementation of the computational microscope. I report the images obtained using the microscope of scattering and reflective targets. Finally, calculation of the effects of a turbulent atmosphere on the operation of the microscope are derived and demonstrated with experimental data, and a new approach to measuring the turbulent atmosphere was developed