Novel active sweat pores based liveness detection techniques for fingerprint biometrics

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Liveness detection in automatic fingerprint identification systems (AFIS) is an issue which still prevents its use in many unsupervised security applications. In the last decade, various hardware and software solutions for the detection of liveness from fingerprints have been proposed by academic research groups. However, the proposed methods have not yet been practically implemented with existing AFIS. A large amount of research is needed before commercial AFIS can be implemented. In this research, novel active pore based liveness detection methods were proposed for AFIS. These novel methods are based on the detection of active pores on fingertip ridges, and the measurement of ionic activity in the sweat fluid that appears at the openings of active pores. The literature is critically reviewed in terms of liveness detection issues. Existing fingerprint technology, and hardware and software solutions proposed for liveness detection are also examined. A comparative study has been completed on the commercially and specifically collected fingerprint databases, and it was concluded that images in these datasets do not contained any visible evidence of liveness. They were used to test various algorithms developed for liveness detection; however, to implement proper liveness detection in fingerprint systems a new database with fine details of fingertips is needed. Therefore a new high resolution Brunel Fingerprint Biometric Database (B-FBDB) was captured and collected for this novel liveness detection research. The first proposed novel liveness detection method is a High Pass Correlation Filtering Algorithm (HCFA). This image processing algorithm has been developed in Matlab and tested on B-FBDB dataset images. The results of the HCFA algorithm have proved the idea behind the research, as they successfully demonstrated the clear possibility of liveness detection by active pore detection from high resolution images. The second novel liveness detection method is based on the experimental evidence. This method explains liveness detection by measuring the ionic activities above the sample of ionic sweat fluid. A Micro Needle Electrode (MNE) based setup was used in this experiment to measure the ionic activities. In results, 5.9 pC to 6.5 pC charges were detected with ten NME positions (50μm to 360 μm) above the surface of ionic sweat fluid. These measurements are also a proof of liveness from active fingertip pores, and this technique can be used in the future to implement liveness detection solutions. The interaction of NME and ionic fluid was modelled in COMSOL multiphysics, and the effect of electric field variations on NME was recorded at 5μm -360μm positions above the ionic fluid.This study is funded by the University of Sindh, Jamshoro, Pakistan and the Higher Education Commission of Pakistan

Magnetic field and temperature sensing with atomic-scale spin defects in silicon carbide

Quantum systems can provide outstanding performance in various sensing applications, ranging from bioscience to nanotechnology. Atomic-scale defects in silicon carbide are very attractive in this respect because of the technological advantages of this material and favorable optical and radio frequency spectral ranges to control these defects. We identified several, separately addressable spin-3/2 centers in the same silicon carbide crystal, which are immune to nonaxial strain fluctuations. Some of them are characterized by nearly temperature independent axial crystal fields, making these centers very attractive for vector magnetometry. Contrarily, the zero-field splitting of another center exhibits a giant thermal shift of -1.1 MHz/K at room temperature, which can be used for thermometry applications. We also discuss a synchronized composite clock exploiting spin centers with different thermal response.Comment: 8 pages, 7 figure

Measurement of the principal singular point in contact and contactless fingerprint images by using computational intelligence techniques

Biometric systems identify individuals by comparison of the individual biometric traits, such as the fingerprint patterns. In the literature, many relevant methods are based on the localization of a reference \u201cpivot\u201d point of the fingerprint, called principal singular point (PSP). Most of the time, the PSP is selected from the list of the estimated singular points (SPs) that are identified by specific local patterns of the fingerprint ridges, called cores and deltas. The challenge is to provide an automatic method capable to select the same PSP from different images of the same fingertip. In this paper, we propose a technique that estimates the position of all the singular points by processing the global structure of the ridges and extracting a specific set of features. The selection of the reference point from the candidate list is then obtained by processing the extracted features with computational intelligence classification techniques. Experiments show that the method is accurate and it can be applied on contact and contact-less image types

CO2 packing polymorphism under confinement in cylindrical nanopores

We investigate the effect of cylindrical nano-confinement on the phase behaviour of a rigid model of carbon dioxide using both molecular dynamics and well tempered metadynamics. To this aim we study a simplified pore model across a parameter space comprising pore diameter, CO2-pore wall potential and CO2 density. In order to systematically identify ordering events within the pore model we devise a generally applicable approach based on the analysis of the distribution of intermolecular orientations. Our simulations suggest that, while confinement in nano-pores inhibits the formation of known crystal structures, it induces a remarkable variety of ordered packings unrelated to their bulk counterparts, and favours the establishment of short range order in the fluid phase. We summarise our findings by proposing a qualitative phase diagram for this model

Biological applications of multimodal imaging involving Raman and 4Pi Raman microscopy

Raman microscopy is becoming an increasingly important label-free imaging technique. It proved to be a viable tool for life science applications allowing to analyze bacteria, cells, and tissues at the molecular level. Combining Raman microscopy with complementary imaging modalities and techniques is explored here to: (1) analyze mild traumatic brain injury (mTBI) in a combination with magnetic resonance imaging (MRI) for detecting mild, and invisible to medical imaging techniques, brain tissue damage; (2) reveal complementarity of Raman and fluorescence microscopy approaches for investigating and tracking bovine lactoferrin inside calf rectal epithelial cells in the presence of enterohemorrhagic Escherichia coli (EHEC); (3) apply Raman microscopy along-side the molecular analysis approaches (such as scanning transmission electron microscopy-energy dispersive X-ray (STEM-EDX), low energy X-ray fluorescence (LEXRF), nanoscale secondary ion mass spectrometry (Nano-SIMS)) to uncover the origin of the long-range conductance in cable bacteria; (4) develop multifunctional surface enhanced Raman scattering (SERS) platform based on calcium carbonate particles for enhancing a weak Raman scattering signal of biomolecules as well as to apply Raman microscopy for particle detection in vivo in Caenorhabditis elegans (C. elegans) worms; and (5) combine Raman microscopy and atomic force microscopy (AFM) to track Chlamydia psittaci in cells. Analysis of described above samples and phenomena is based on Raman molecular fingerprint images, where, similarly to fluorescence light microscopy, the resolution is limited by diffraction of light. Therefore, efforts are also put to enhance the resolution of Raman microscopy-based imaging by adding a 4Pi configuration to a confocal Raman microscope. As a result, a possibility to enhance the axial (also called longitudinal) resolution is investigated by constructing a 4Pi confocal Raman microscope, which is also applied to study bacteria inside cells. Results presented in this work emphasize the added value of multimodal microscopy approaches, particularly involving Raman microscopy, in a broad range of applications in bioengineering, biomedicine, and biology

Vibrational Imaging at the Nanoscale: Surpassing the Diffraction Limit Using Tip-Enhanced Raman Spectroscopy

A deep understanding of the chemical composition of surfaces, interfaces or nanoscale structure with a high spatial resolution is an important goal in nanoscience and nanotechnology. Structural information can be collected using a variety of high spatial resolution techniques such as atomic force microscopy (AFM), scanning tunneling microscopy (STM), scanning electron microscopy (SEM), or transmission electron microscopy (TEM). Nevertheless, these methods do not offer molecular information such as vibrational spectroscopy techniques that allow one to collect molecular or lattice vibrations yielding to a precise picture of the molecular interactions in bulk materials as well as in surfaces and interfaces. Unfortunately optical spectroscopy techniques are limited in terms of spatial resolution and sensitivity due to the poor signal/noise ratio of the localized measurement. Surface- and tip-enhanced Raman spectroscopy (SERS and TERS) are advanced spectroscopic techniques, which are becoming widely used and show a great potential for the structural characterisation of biological systems. Surface-enhanced spectroscopy (SERS) was developed to improve the sensitivity of the chemical measurements by using rough silver or gold surfaces. The challenge of the simultaneous improvement of the spatial resolution and sensitivity was addressed by combining high resolution optical microscopy with the high sensitivity of surface-enhanced spectroscopy and was termed tip-enhanced Raman spectroscopy (TERS). In this thesis, gap-mode TERS is developed for the study of a variety of materials. TERS is used in conjunction with gold nanoplates to serve as an ultraflat substrate that can possibly be functionalized. TERS investigation of monolayers adsorbed onto gold nanoplates such as alkoxy substituted azobenzene thiol and 4-nitrothiophenol is conducted. The monolayer is probed with a silver coated AFM tip in order to obtain the largest electromagnetic field enhancement and the effect of the excitation (linearly or radially polarized) is conducted. TERS is also used to probe graphene flakes and differentiate the edges of a few-layer graphene flakes with a spatial resolution better than 20 nm. Last, TERS was used to investigate single DNA molecules deposited onto gold nanoplates. The DNA, cDNA and pure plasmid were investigated with TERS probing the distribution of nucleobases at a specific location with a spatial resolution which was, in the best conditions below 10 nm