Jeremy M. Dawson

Nanotopographical Modulation of Cell Function through Nuclear Deformation

Although nanotopography has been shown to be a potent modulator of cell behavior, it is unclear how the nanotopographical cue, through focal adhesions, affects the nucleus, eventually influencing cell phenotype and function. Thus, current methods to apply nanotopography to regulate cell behavior are basically empirical. We, herein, engineered nanotopographies of various shapes (gratings and pillars) and dimensions (feature size, spacing and height), and thoroughly investigated cell spreading, focal adhesion organization and nuclear deformation of human primary fibroblasts as the model cell grown on the nanotopographies. We examined the correlation between nuclear deformation and cell functions such as cell proliferation, transfection and extracellular matrix protein type I collagen production. It was found that the nanoscale gratings and pillars could facilitate focal adhesion elongation by providing anchoring sites, and the nanogratings could orient focal adhesions and nuclei along the nanograting direction, depending on not only the feature size but also the spacing of the nanogratings. Compared with continuous nanogratings, discrete nanopillars tended to disrupt the formation and growth of focal adhesions and thus had less profound effects on nuclear deformation. Notably, nuclear volume could be effectively modulated by the height of nanotopography. Further, we demonstrated that cell proliferation, transfection, and type I collagen production were strongly associated with the nuclear volume, indicating that the nucleus serves as a critical mechanosensor for cell regulation. Our study delineated the relationships between focal adhesions, nucleus and cell function and highlighted that the nanotopography could regulate cell phenotype and function by modulating nuclear deformation. This study provides insight into the rational design of nanotopography for new biomaterials and the cell-substrate interfaces of implants and medical devices.

Ascertaining Human Identity in Night Environments

Understanding patterns of human activity from the fusion of multimodal sensor surveillance sources is an important capability. Most related research emphasizes improvement in the performance of biometric systems in controlled conditions characterized by suitable lighting and favorable acquisition distances. However, the need for monitoring humans in night environments is of equal if not greater importance. This chapter will present techniques for the extraction, processing and matching of biometrics under adverse night conditions in the presence of either natural or artificial illumination. Our work includes capture, analysis and evaluation of a broad range of electromagnetic bands suitable for night-time image acquisition, including visible light, near infrared (IR), extended near IR and thermal IR. We develop algorithms for human detection and tracking from night-time imagery at ranges between 5 and 200 meters. Identification algorithms include face, iris, and gait recognition, supplemented by soft biometric features. Our preliminary research indicates the challenges in performing human identification in night-time environments.

Through-wafer optical probe characterization for microelectromechanical systems positional state monitoring and feedback control

Implementation of closed-loop microelectromechanical sys- tem (MEMS) control enables mechanical microsystems to adapt to the demands of the environment that they are actuating, opening a broad range of new opportunities for future MEMS applications. Integrated op- tical microsystems have the potential to enable continuous in situ optical interrogation of MEMS microstructure position fully decoupled from the means of mechanical actuation that is necessary for realization of feed- back control. We present the results of initial research evaluating through-wafer optical microprobes for surface micromachined MEMS in- tegrated optical position monitoring. Results from the through-wafer free- space optical probe of a lateral comb resonator fabricated using the multiuser MEMS process service (MUMPS) indicate significant positional information content with an achievable return probe signal dynamic range of up to 80% arising from film transmission contrast. Static and dynamic deflection analysis and experimental results indicate a through- wafer probe positional signal sensitivity of 40 mV/mm for the present setup or 10% signal change per micrometer. A simulation of the applica- tion of nonlinear sliding control is presented illustrating position control of the lateral comb resonator structure given the availability of positional state information.

Investigating gait recognition in the short-wave infrared (SWIR) spectrum: dataset and challenges

In the biometrics community, challenge datasets are often released to determine the robustness of state-of-the- art algorithms to conditions that can confound recognition accuracy. In the context of automated human gait recognition, evaluation has predominantly been conducted on video data acquired in the active visible spectral band, although recent literature has explored recognition in the passive thermal band. The advent of sophisticated sensors has piqued interest in performing gait recognition in other spectral bands such as short-wave infrared (SWIR), due to their use in military-based tactical applications and the possibility of operating in nighttime environments. Further, in many operational scenarios, the environmental variables are not controlled, thereby posing several challenges to traditional recognition schemes. In this work, we discuss the possibility of performing gait recognition in the SWIR spectrum by first assembling a dataset, referred to as the WVU Outdoor SWIR Gait (WOSG) Dataset, and then evaluate the performance of three gait recognition algorithms on the dataset. The dataset consists of 155 subjects and represents gait information acquired under multiple walking paths in an uncontrolled, outdoor environment. Detailed experimental analysis suggests the benefits of distributing this new challenging dataset to the broader research community. In particular, the following observations were made: (a) the importance of SWIR imagery in acquiring data covertly for surveillance applications; (b) the difficulty in extracting human silhouettes in low-contrast SWIR imagery; (c) the impact of silhouette quality on overall recognition accuracy; (d) the possibility of matching gait sequences pertaining to different walking trajectories; and (e) the need for developing sophisticated gait recognition algorithms to handle data acquired in unconstrained environments.

GaN Photonic Crystal-Based, Enhanced Fluorescence Biomolecule Detection System

The need for small form factor, portable biosensing platforms is prevalent across a wide range of medical, environmental, and defense applications. This paper presents the design of a novel, integrated optofluidic photonic crystal biosensor architecture that shows potential for meeting the single molecule detection requirements of these application areas. GaN is being targeted as the photonic crystal slab material due to its transparency in the visible spectral range and also the potential for creating high aspect ratio photonic crystal lattices via polarity inverted MBE growth. Results of optical modeling efforts indicating 10-15x resonant enhancement of fluorescent emission and polarity inversion GaN growth techniques will be discussed.

SWIR Imaging for Facial Image Capture through Tinted Materials

The use of short wave infrared (SWIR) imaging and illumination technology is at the forefront of system development for military and law enforcement in both night and daytime operational scenarios1 2 3 4 . Along with enabling nighttime operations, a secondary benefit of SWIR imaging is that it offers the possibility to capture images through tinted materials, such as tinted architectural or automotive glass and sunglass lenses5. The use of SWIR technology introduces challenges to facial recognition when comparing cross-spectrally from a visible gallery to images captured in the SWIR6. The challenges of SWIR facial recognition are further compounded by the presence of tinted materials in the imaging path due to varying material types, lighting conditions, and viewing angle. The paper discusses material and optical characterization efforts undertaken to understand the effects of temperature, interior and exterior light sources, and viewing angle on the quality of facial images captured through tinted materials. Temperature vs. spectrum curves are shown for tinted architectural, automotive, and sunglass materials over the range of -10 to 55C. The results of imaging under various permutations of interior and exterior lighting, along with viewing angle, are used to evaluate the efficacy of eye detection for cross-spectral facial recognition under these conditions.

Automated classification of mislabeled near-infrared left and right iris images using convolutional neural networks

In this paper, we propose a Convolutional Neural Network (CNN) with unified architecture (no need to re-design it for each unique iris database used) that operates well in a diverse set of iris databases. The CNN is designed to automatically recognize mislabeled left and right iris images by iris recognition system operators, and thus, extend the capabilities of a conventional iris recognition system. Our proposed approach is composed of three steps. First, for each iris database used as input, a CNN is trained using part of the database. Second, an empirical parameter optimization study is conducted so that classification performance is acceptable. Finally, the proposed classifier is tested on the remaining images of the same database used for training. The performance of the proposed network is evaluated on small- and large-scale iris databases, including the NISTs Iris Challenge Evaluation (ICE), LG ICAM 4000 iris, the CASIA Lamp, and the Pupil Light Reflex (PLR) databases. Experimental results show that independent of the databases used or whether the classification performance is tested on either a left-or right-side dataset, our approach results in a classification performance ranging from 97.5 to 100%.

Optofluidic photonic crystals for biomolecular fluorescence enhancement : a bottom-up approach for fabricating GaN-based biosensors

The application of photonic crystals in biosensor applications has lead to the development of highly sensitive and selective sensor elements. The research efforts undertaken by this group have led to the development of a photonic crystal transducer that acts as a waveguide, nanofluidic flow channel, and resonant defect cavity. This sensor architecture shows promise for greatly enhancing the emission of naturally fluorescent or fluorescently-labeled biomolecules. Due to its transparency in the visible regime, GaN is a viable candidate for this photonic crystal biosensor application. This paper provides an overview of the sensor architecture as well as a discussion of one particular bottom-up approach to its fabrication. Molecular Beam Epitaxy (MBE) growth of heavily Mg doped GaN can result in inversion of the surface polarity from Ga-polar to N-polar GaN. This bottom-up approach includes patterning and etching of the Mg inversion layer, followed by re-growth of the opposite polarity to produce periodically poled GaN. Subsequent wet etching of N-polar regions then produces a GaN based photonic crystal structure. This process shows promise for achieving high aspect ratio, highly anisotropic nanostructures.

Integrated otpical monitoring of MEMS for closed-loop control

Robust control and failure assessment of MEMS employed in physically demanding, mission critical applications will allow for higher degrees of quality assurance in MEMS operation. Device fault detection and closed-loop control require detailed knowledge of the operational states of MEMS over the lifetime of the device, obtained by a means decoupled from the system. Preliminary through-wafer optical monitoring research efforts have shown that through-wafer optical probing is suitable for characterizing and monitoring the behavior of MEMS, and can be implemented in an integrated optical monitoring package for continuous in-situ device monitoring. This presentation will discuss research undertaken to establish integrated optical device metrology for closed-loop control of a MUMPS fabricated lateral harmonic oscillator. Successful linear closed-loop control results using a through-wafer optical microprobe position feedback signal will be presented. A theoretical optical output field intensity study of grating structures, fabricated on the shuttle of the resonator, was performed to improve the position resolution of the optical microprobe position signal. Through-wafer microprobe signals providing a positional resolution of 2 μm using grating structures will be shown, along with initial binary Fresnel diffractive optical microelement design layout, process development, and testing results. Progress in the design, fabrication, and test of integrated optical elements for multiple microprobe signal delivery and recovery will be discussed, as well as simulation of device system model parameter changes for failure assessment.

Grating-enhanced through-wafer optical microprobe for microelectromechanical system high-resolution optical position feedback.

We present modeling and experimental results from the use of a 1310-nm-wavelength through-wafer optical microprobe in conjunction with a microstructure grating to monitor the motion of a lateral comb resonator stage. The optical signal that results from shuttle interaction with the microprobe beam exhibits a peak-to-valley dynamic range that corresponds to 2-microm microstructure displacement, facilitating submicrometer positional resolution on digitization. This signal was used to achieve microstructure positional feedback and effective microsystem model parameter extraction, which are essential for structure control and model-based fault detection.