Nano handling and measurement of biological cells in culture

A thesis submitted to the University of Bedfordshire in partial fulfillment of the requirements for the degree of Doctor of PhilosophyThis thesis systematically investigates the nano handling and measurement techniques for biological cells in culture and studies the techniques to realize innovative and multi-functional applications in biomedicine. Among them, the technique based on AFM is able to visualize and quantify the dynamics of organic cells in culture on the nano scale. Especially, the cellular shear adhesion force on the various locations of biological cells was firstly accurately measured in the research of the cell-substrate interaction in terms of biophysical perspective. The innovative findings are conductive to study the cell-cell adhesion, the cell-matrix adhesion which is related to the cell morphology structure, function, deformation ability and adhesion of cells and better understand the cellular dynamic behaviors. Herein, a new liquid-AFM probe unit and an increment PID control algorithm were implemented suitable for scanning the cell samples under the air conditions and the liquid environments. The influence between the surface of sample and the probe, and the damage of probe during the sample scanning were reduced. The proposed system is useful for the nano handling and measurement of living cells. Besides, Besides, to overcome the limitations of liquid-AFMs, the multiple optical tweezers were developed to integrate with the liquid-AFM. The technique based on laser interference is able to characterize the optical trap stiffness and the escape velocity, especially to realize the capture and sorting of multiple cells by a polarization-controlled periodic laser interference. It can trap and move hundreds of cells without physical contact, and has broad application prospects in cytology. Herein, a new experimental method integrated with the positioning analysis in the Z direction was used to improve the fluid force method for the calibration and characterize the mechanical forces exerted on optical traps and living cells. Moreover, a sensitive and highly efficient polarization-controlled three-beam interference set-up was developed for the capture and sorting of multiple cells. By controlling the polarization angles of the beams, various intensity distributions and different sizes of dots were obtained. Subsequently, we have experimentally observed multiple optical tweezers and the sorting of cells with different polarization angles, which are in accordance with the theoretical analysis

Development of microcantilever sensors for cell studies

Micro- and nano- electromechanical devices such as microcantilevers have paved the way for a large variety of new possibilities, such as the rapid diagnosis of diseases and a high throughput platform for drug discovery. Conventional cell assay methods rely on the addition of reagents, disrupting the measurement, therefore providing only the endpoint data of the cell growth experiment. In addition, these methods are typically slow to provide results and time and cost consuming. Therefore, microcantilever sensors are a great platform to conduct cell culturing experiments for cell culture, viability, proliferation, and cytotoxicity monitoring, providing advantages such as being able to monitor cell kinetics in real time without requiring external reagents, in addition to being low cost and fast, which conventional cell assay methods are unable to provide. This work aims to develop and test different types of microcantilever biosensors for the detection and monitoring of cell proliferation. This approach will overcome many of the current challenges facing microcantilever biosensors, including but not limited to achieving characteristics such as being low cost, rapid, easy to use, highly sensitive, label-free, multiplexed arrays, etc. Microcantilever sensor platforms utilizing both a single and scanning optical beam detection methods were developed and incorporated aspects such as temperature control, calibration, and readout schemes. Arrays of up to 16 or 32 microcantilever sensors can be simultaneously measured with integrated microfluidic channels. The effectiveness of these cantilever platforms are demonstrated through multiple studies, including examples of growth induced bending of polyimide cantilevers for simple real-time yeast cell measurements and a microcantilever array for rapid, sensitive, and real-time measurement of nanomaterial toxicity on the C3A human liver cell line. In addition, other techniques for microcantilever arrays and microfluidics will be presented along with demonstrations for the ability for stem cell growth monitoring and pathogen detection

Investigation of optical near field using near field scanning optical microscopy

Conventional optical imaging techniques have a fundamental resolution limit due to the diffraction limit of light. The advances of science and technology on the nanoscale demand a new tool for characterization. The Near Field Scanning Optical Microscopy (NSOM) has been developed to tackle certain aspects of this problem. The work presented here applies different types of NSOM to explore the near field distribution of metal plasmonic nanostructures.^ Ridge apertures with shapes like bowtie and C can be used to focus light into sub-diffraction limit spot with enhancement. This localization of the field near the exit of a bowtie aperture is investigated with a home built aperture NSOM. The experiment results confirm the confinement of focused light spot and the fast decay nature of optical near fields. To further increase the transmission efficiency, a concentric grating structure is added to the bowtie aperture. Near field examination of the transmitted energy with NSOM shows a factor of 15 augment in the transmission.^ To achieve a better resolution, an alternative method is also investigated. The scattering (apertureless) NSOM is demonstrated to have optical resolution only limited by the radius of its tip apex. The physics behind scattering NSOM is explained and the difficulty of its implementation investigated. Among the different proposed methods, the pseudo-heterodyne interferometric method is chosen and applied in this work.^ A scattering NSOM has been built based on a commercial AFM. With the home-built s-NSOM setup, the optical responses of several different plasmonic structures have been studied. The examination of a sample with a circular aperture array shows that the interferometric pseudo-heterodyne method is indeed effective in suppressing the background noise. The s-NSOM has also been used to investigate the formation mechanism of interferometric patterns observed during the measurement of a single nanoslit. In the end, a revisit of the 3-D optical field distribution of the bowtie aperture has been conducted, with a focus on the Ez field. For s-NSOM measurements, both the amplitude and phase information are obtained, enabling vector analysis of the optical fields

Optical trapping: optical interferometric metrology and nanophotonics

The two main themes in this thesis are the implementation of interference methods with optically trapped particles for measurements of position and optical phase (optical interferometric metrology) and the optical manipulation of nanoparticles for studies in the assembly of nanostructures, nanoscale heating and nonlinear optics (nanophotonics). The first part of the thesis (chapter 1, 2) provides an introductory overview to optical trapping and describes the basic experimental instrument used in the thesis respectively. The second part of the thesis (chapters 3 to 5) investigates the use of optical interferometric patterns of the diffracting light fields from optically trapped microparticles for three types of measurements: calibrating particle positions in an optical trap, determining the stiffness of an optical trap and measuring the change in phase or coherence of a given light field. The third part of the thesis (chapters 6 to 8) studies the interactions between optical traps and nanoparticles in three separate experiments: the optical manipulation of dielectric enhanced semiconductor nanoparticles, heating of optically trapped gold nanoparticles and collective optical response from an ensemble of optically trapped dielectric nanoparticles

High-quality dense 3D point clouds with active stereo and a miniaturizable interferometric pattern projector

We have built and characterized a compact, simple and flexible 3D camera based on interferometric fringe projection and stereo reconstruction. The camera uses multi-frame active stereo as basis for 3D reconstruction, providing full-field 3D images with 3D measurement standard deviation of 0.09 mm, 12.5 Hz 3D image capture rate and 3D image resolution of 500 × 500 pixels. Interferometric projection enables a compact, low-power projector that consumes < 1 W of electrical power. The key component in the projector, a movable micromirror, has undergone initial vibration, thermal vacuum cycling (TVAC) and radiation testing, with no observed component degradation. The system's low power, small size and component longevity makes it well suitable for space applications.publishedVersio

Development of mirrors made of chemically tempered glass foils for future X-ray telescopes

Thin slumped glass foils are considered good candidates for the realization of future X-ray telescopes with large effective area and high spatial resolution. However, the hot slumping process affects the glass strength, and this can be an issue during the launch of the satellite because of the high kinematical and static loads occurring during that phase. In the present work we have investigated the possible use of Gorilla glass (produced by Corning), a chemical tempered glass that, thanks to its strength characteristics, would be ideal. The un-tempered glass foils were curved by means of an innovative hot slumping technique and subsequently chemically tempered. In this paper we show that the chemical tempering process applied to Gorilla glass foils does not affect the surface micro-roughness of the mirrors. On the other end, the stress introduced by the tempering process causes a reduction in the amplitude of the longitudinal profile errors with a lateral size close to the mirror length. The effect of the overall shape changes in the final resolution performance of the glass mirrors was studied by simulating the glass foils integration with our innovative approach based on glass reinforcing ribs. The preliminary tests performed so far suggest that this approach has the potential to be applied to the X-ray telescopes of the next generation.Comment: Accepted for publication in Experimental Astronomy. Author's accepted manuscript posted to arXiv.org as permitted by Springer's Self-Archiving Polic

Robust optical diffractive technique to read out cantilever defl�ection

Microcantilevers have now been used successfully for over a decade. New assays are being developed and tested continuously but the technique has not arrived in hospitals and surgeries yet. The main obstacle was that a robust and reliable readout system which does not need intricate alignment before each measurement was not available. Therefore cantilever devices have only been used in university laboratories. The aim of the research presented in this thesis is to provide a diffractive optical readout for cantilever bending that is rapid, robust and easy to use. The diffractive readout discovered during my PhD involves a laser illuminating the entire cantilever and additionally parts of the chip base to which it is attached. The laser light diffracted from the cantilever contains information that allows a distinction to be made between tilting and bending of the cantilever. Additionally, measurements of the absolute tilting and bending can be performed and the time needed for aligning the cantilever chip in the laser beam is reduced to a minimum. This thesis describes the tools used to develop the diffractive readout and presents experimental results. First, a simulation was programmed to predict results and optimise experimental conditions. Second, an experimental setup was built from scratch and a new ow cell designed which was needed for transmission mode experiments. Third, test experiments in air were performed using a transmissive and a reflective diffraction approach. Fourth and finally, the applicability of the diffractive readout was shown by demonstrating that the binding of the antibiotic vancomycin to a glycopeptide could be measured successfully. I hope that the invention presented in this thesis will help to commercialise the cantilever setup and make it attractive for the use in hospital and surgeries speeding up diagnostic steps from days down to a few minutes. This thesis lays the cornerstone of the discovered, patented and tested optical diffractive readout technique for cantilever based biosensors. Optimisation of the experiment, being very important and essential, has to be focused on in the future and is not dealt with in detail in here

Tune-out measurement in lukewarm lithium with phase-patterned atom interferometry

Atom interferometry deploys atoms as sensors, delivering precision measurements that span the gamut of physics. Laser-cooled samples simplify uniform detection strategies and allow meticulous control over degrees of freedom and systematic effects. Advanced cooling and interferometry techniques do apply readily to a few atomic species, but they leave behind a large class of species otherwise suited for precision sensing. This thesis describes atom interferometry with a sample of lukewarm $^7$Li, near the Doppler temperature. High thermal speeds demand rapid atom optics and complicate detection. We nevertheless develop interferometer techniques that considerably relax cooling requirements, including a recoil-sensitive scheme capable of measuring the fine-structure constant that takes advantage of $^7$Li's low mass. We also establish a phase-patterning protocol to inscribe and sense spatially-varying phases with matter-wave interferometers whose sample sizes exceed the arm separation. Phase patterning forms the basis of the first precision measurement of $^7$Li's red tune-out wavelength, the wavelength where AC Stark shifts from the $D$-line transitions cancel and the polarizability vanishes. Our measurement registers a 3-$\sigma$ tension with \emph{ab initio} atomic theory regarding the tensor-shifted tune-out wavelength and a 2-$\sigma$ tension regarding the size of the tensor shift, but agrees with theory regarding the scalar tune-out wavelength. These results motivate further work on lithium's polarizability, enable direct measurements of hyperpolarizability, and empower an assortment of future applications of phase patterning in matter-wave interferometry

Construction of a quantum gas microscope for fermionic atoms

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 83-85).This thesis reports the construction of a novel apparatus for experiments with ultracold atoms in optical lattices: the Fermi gas microscope. Improving upon similar designs for bosonic atoms, our Fermi gas microscope has the novel feature of being able to achieve single-site resolved imaging of fermionic atoms in an optical lattice; specifically, we use fermionic potassium-40, sympathetically cooled by bosonic sodium-23. In this thesis, several milestones on the way to achieving single-site resolution are described and documented. First, we have tested and mounted in place the imaging optics necessary for achieving single-site resolution. We set up separate 3D magnetooptical traps for capturing and cooling both ²³Na and ⁴⁰K. These species are then trapped simultaneously in a plugged quadrupole magnetic trap and evaporated to degeneracy; we obtain a sodium Bose-Einstein condensate with about a million atoms and a degenerate potassium cloud cooled to colder than 1 [mu]K. Using magnetic transport over a distance of 1 cm, we move the cold cloud of atoms into place under the high-resolution imaging system and capture it in a hybrid magnetic and optical-dipole trap. Further evaporation in this hybrid trap performed by lowering the optical trap depth, and the cooled atoms are immersed in an optical lattice, the setup and calibration of which is also described here. Finally, we cool the atoms with optical molasses beams while in the lattice, with the imaging optics collecting the fluoresence light for high-resolution imaging. With molasses cooling set up, single-site fluoresence imaging of bosons and fermions in the same experimental apparatus is within reach.by Vinay Venkatesh Ramasesh.M. Eng

Method and Apparatus for a Differential Localized Microscopy System Based on Position Sensitive Detector

A precise measurement of position using a Position Sensitive Detector (PSD) is fundamental in mitigating the geometric error factors that are caused by the pincushion-type distortion of these sensors. These errors can be addressed by implementing a differential localized method to significantly reduce signal to noise ratio (SNR) in PSD and the microscopy system. The differential method based on Time difference of Arrival (TDoA) is proposed and implemented in this research. The simulation and the actual results of the system further confirm the significant improvement in accuracy and precision of the system