Optical-based Techniques Research Articles

Pressure distributions on swept/unswept wings using pressure sensitive paint

Pressure sensitive paint (PSP) is an optical-based technique for full-field pressure measurements. A polymer-ceramic PSP, Ru(dpp), with a porous material is used and is applied onto a Mylar tape which affixed to the model surface of NACA 0012 and ONERA M6 wings. The PSP results agree with the data using conventional pressure measurements reasonably well.

A non-contact approach for surface roughness prediction in CNC turning using a linear regression model

At present, the combination of non-contact type optical techniques and machine vision systems has a huge significance in the assessment of surface roughness. The non-contact measurement methods seem to have greater advantages over the conventional stylus method. Traditionally used contact-type surface roughness measurement technique assesses the roughness of machined component in a single line which is overcome by optical-based techniques and machine vision techniques with the capability to assess the whole machined surface. This paper deals with selected contact type stylus method and non-contact type machine vision methods for components prepared by turning of AISI 1040 steel at a variety of feed rates. The correlations have been developed between two dimensional (2D) surface roughness parameter and texture features for the components. The 2D surface roughness parameters have been recorded using a contact-type surface profilometer. On the other hand, the texture features have been extracted using a Gray level co-occurrence matrix algorithm (GLCM) and machine vision system. The correlation has been developed between extracted texture features of machined surfaces and measured 2D surface roughness parameters. The linear regression analysis has been performed in order to predict the surface roughness of machined components. The comparative results reveal a maximum measurement difference of 15% between contact types and presented a non-contact type assessment.

Going beyond conventional parameters to unveil sperm quality in fish: the use of fibre optic technology to assess mitochondrial respiratory performance.

ABSTRACTSperm fertilisation success depends on both intrinsic quality and the interactions with the surrounding reproductive fluids. In several fish species, these interactions have a variable effect on sperm performance. Although specific responses to reproductive fluids may depend on intrinsic differences in sperm quality, variations in the traditionally recorded sperm functional traits do not fully account for the observed patterns. New methods to enhance the evaluation of sperm quality may prove to be valuable at both applied and theoretical levels, by improving the breeding protocol of reared species and the understanding of mating success in sperm competition contexts. Here we develop a fibre optic-based technique, also adequate for small ejaculate samples, to test the role of mitochondrial respiratory efficiency in deciphering sperm performance variability. We purposely used as model the grass goby, Zosterisessor ophiocephalus, a fish with guard-sneaker mating tactics where the sperm in each male tactic have similar intrinsic qualities (velocity, viability, ATP content), but sneakers' sperm exploit territorial males' seminal fuid, overall displaying better fertilization ability. We found that sperm differed in their mitochondrial respiratory efficiency, which was higher in sneakers’ sperm compared to territorial ones. This result draws the attention to an indicator of sperm quality that might be helpful in disentangling the mechanisms driving sperm-reproductive fluid interactions.

Brownian Disks Lab: Simulating time-lapse microscopy experiments for exploring microrheology techniques and colloidal interactions

Brownian Disks Lab (BDL) is a Java-based application for the real-time generation and visualization of the motion of two-dimensional Brownian disks using Brownian Dynamics (BD) simulations. This software is designed to emulate time-lapse microscopy experiments of colloidal fluids in quasi-2D situations, such as sedimented layers of particles, optical trap confinement, or fluid interfaces. Microrheology of bio-inspired fluids through optical-based techniques such as videomicroscopy is a classic tool for obtaining the mechanical properties and molecular behavior of these materials. The results obtained by microrheology notably depend of the time-lapse value of the videomicroscopy setup, therefore, a tool to test the influence of the lack of statistics by simulating Brownian objects in experimental-like situations is needed. We simulate a colloidal fluid by using Brownian Dynamics (BD) simulations, where the particles are subjected to different external applied forces and inter-particle interactions. This software has been tested for the analysis of the microrheological consequences of attractive forces between particles [1], the influence of image analysis on experimental microrheological results [2], and to explore experimental diffusion with optical tweezers [3]. The output results of BDL are directly compatible with the format used by standard microrheological algorithms [4]. In a context of microrheology of complex bio-inspired fluids, we use this tool here to study if the lack of statistics may influence the observed potential of a bead trapped by optical tweezers. Program summaryProgram Title: Brownian Disks Lab (BDL)Program Files doi:http://dx.doi.org/10.17632/dbwzdkttkb.1Licensing provisions: GPLv3Programming language: Java (JDK 7 and above)Supplementary material: We provide a detailed user manual which describes how to use BDL, the theoretical basis of Brownian dynamics simulations, the particle–particle interactions implemented in this software, and additional details and explanations regarding the developed code.Nature of problem: By using time-lapse microscopy experiments (video-microscopy), we can observe the Brownian motion of colloidal particles under different particle–particle interactions and external forces. Sedimented quasi-two-dimensional layers, fluid interfaces, or optically trapped particles can be considered as two-dimensional colloidal systems. The centers of mass of the colloidal objects are subsequently obtained by the image analysis of the time-lapsed images stored. We need an application to generate an ideal real-time motion of colloidal objects in a simple fluid, providing the position of the particles without the need of image analysis. This software should allow to inspect, before the experiments, the general behavior of a colloidal fluid, including visual inspection of the particles’ movement. Using this application, we should be able to analyze the collective motion of the Brownian objects, the influence of different inter-particle forces, and the limitations of the experimental setup, e.g., the effect of image analysis in the results obtained.Solution method: BDL performs the simulation of Brownian 2D disks contained in a transparent medium with a constant viscosity value. The theoretical scheme allows us to introduce external forces in the disks for testing different experimental conditions, and the interactions observed in experiments on colloidal physics (Einstein, 1905; Xin et al., 2016). We use a computational multi-platform environment without high computing requirements since a small number of particles (n≤500) and small concentrations are typical of time-lapse microscopy experiments. The output data is analogous to a video-microscopy setup: the required statistical quantities can be later calculated from the particles’ positions using microrheology standard algorithms (Bevan and Eichmann, 2011). BDL has been developed using Easy Java/JavaScript Simulations (EjsS) (Dinsmore et al., 2002), a software which allows to simplify the code generation and the visualization of simulated objects. Java allows to run the software in any SO without compilation or installation as long as Java Runtime Environment (JRE) is previously installed in the computer.Additional comments including restrictions and unusual features: Requires SO with Java Runtime Environment (JRE) installed.[1] P. Domínguez-García, Europhys. J. E. Soft. Matter. 35, p. 73, 2012.[2] P. Domínguez-García and M. A. Rubio, Appl. Phys. Lett. 102, p. 074101, 2013.[3] M. Pancorbo, M. A. Rubio, P. Domínguez-García, Procedia Comp. Sci.. 108, p. 166–174, 2017.[4] J. C. Crocker and D. G. Grier, J. Colloid Interface Sci. 179, p. 298–310, 1996.

An Optical-Based Technique to Obtain Vibration Characteristics of Rotating Tires

An Optical-Based Technique to Obtain Vibration Characteristics of Rotating Tires

An optical-based technique to obtain operating deflection shapes of structures with complex geometries

Abstract The dynamic characteristics of structures are conventionally obtained by exciting the structure using an impulse hammer or a mechanical shaker and measuring the response using uniaxial or multi-axial accelerometers. However, contact-based sensors can mass-load the structure and do not provide full-field data. Hence, obtaining the true dynamics of the structure using conventional sensors can be challenging. That makes test engineers seek different non-contact techniques that can provide full-field data without mass-loading the structure. Recently, stereo-photogrammetry and three-dimensional digital image correlation (3D DIC) have been adopted to collect operating data for structural analysis. These non-contact optical techniques provide a wealth of distributed data over the entire structure. However, the stereo-camera system is limited by the field-of-view of the cameras; a single pair of DIC cameras may not be able to provide deformation data for the entire structure. Hence, it is challenging to obtain the vibration characteristics of the entire structure. In the current work, a multi-view 3D DIC approach is used and validated to predict the vibrational characteristics of an automotive muffler with a complex structure. A pair of DIC cameras travels over the entire structure to capture the deformation of each field of view. The measured data includes the geometry and displacement data, which is later mapped into a global coordinate system. The measured data in the time domain for each field-of-view is transformed to the frequency domain to extract the operational deflection shapes and resonant frequencies for each field of view. The obtained deflection shapes are stitched together in the frequency domain to extract the operating deflection shapes and resonant frequencies of the automotive body panel with a complex structure.

Perovskite Solar Cells: Imaging Spatial Variations of Optical Bandgaps in Perovskite Solar Cells (Adv. Energy Mater. 7/2019)

In article number 1802790, Daniel Macdonald, Hieu T. Nguyen, and co-workers develop a fast, non-destructive, camera-based method to capture optical bandgap images of perovskite solar cells with micron-scale spatial resolution. This technique allows them to probe relative variations in optical bandgaps across various solar cells, and to resolve optical bandgap inhomogeneity within the same device due to material degradation and impurities. The results are independently confirmed with other optical-based techniques.

Quantum-based vacuum metrology at NIST.

The measurement science in realizing and disseminating the unit for pressure in the International System of Units (SI), the pascal (Pa), has been the subject of much interest at NIST. Modern optical-based techniques for pascal metrology have been investigated, including multi-photon ionization and cavity ringdown spectroscopy. Work is ongoing to recast the pascal in terms of quantum properties and fundamental constants and in so doing, make vacuum metrology consistent with the global trend toward quantum-based metrology. NIST has ongoing projects that interrogate the index of refraction of a gas using an optical cavity for low vacuum, and count background particles in high vacuum to extreme high vacuum using trapped laser-cooled atoms.

Channel temperature measurement in hermetic packaged GaN HEMTs power switch using fast static and transient thermal methods

A GaN-based power device is a superior component for high-frequency and high-efficiency applications and especially for applications that involve megahertz power conversion. In this work, a fast process of static thermal resistance (R th) and transient thermal impedance (Z th) measurements are made and analyzed to determine the thermal characteristics of the channel temperature of a hermetically packaged GaN power device. Five temperature-sensitive parameters (TSPs) are measured at temperatures from 20 to 160 °C. Measurements and statistical analyses included variations with temperature of on-resistance (R on), saturation drain current (I Dsat), drain conductance (g d), threshold voltage (V th), and knee voltage (V knee). The statistical analyses revealed the relationships between the heating curve parameter (R on) and the cooling curve parameters (V knee, I Dsat, g d, and V th). The average thermal resistance values are extracted as follows: Maximum R th is 2.99 °C W−1, minimum R th is 2.92 °C W−1, and the variation among the five TSPs is <3%. Conventional optical-based techniques such as infrared (IR) and micro-Raman thermography are destructive to packaged devices. Therefore, this study developed the two reliable and fast non-destructive methods for estimating channel temperature with the following features: (1) They elucidate static and transient characteristics; (2) they involve heating and cooling; and (3) they evaluate transient thermal impedance (TTI) and safe operating area (SOA). The heating curve method has advantages over cooling curve method in terms of capturing time (40 vs. 400 s, respectively), and a lower power excitation is required to obtain the transient channel temperature response.

The effect of thickness measurement on numerical arterial models

Several optical-based techniques for measuring the sample thickness (ST) of soft tissues have been proposed in the literature to overcome the limits of hand-operated procedures. However, ST measurement still remains arbitrary. The stress calculated during an experimental procedure, usually based on a constant thickness value for all samples, cannot be considered representative of the actual stress experienced by the tissue. Therefore, a new optical methodology to measure ST is proposed and compared to four different thickness estimations. A simplified aortic geometry, under physiologic pulsatile conditions, is used to assess the impact of ST measurement on stress predictions. An additional computational model investigates the effect of such thickness values on critical pressure levels that may instigate aneurysm formation in a homogeneous or artificially modified geometry. Comparing the results obtained for the application of a pulsatile load, wall stress values associated to minimum ST are at least 24kPa inferior to maximum ST. Critical pressure values appear to be inversely proportional to ST estimation: simulations, associated to maximum ST, predict aneurysm formation for pressure levels at least 7kPa inferior to minimum ST outcomes. Finally, the role of the strain-energy function used to fit the experimental data is demonstrated to be fundamental for predictions of aneurysm formation.

High-resolution fast ion microscopy of single whole biological cells

High-resolution microscopy techniques have become an essential tool in both biological and biomedical sciences, enabling the visualization of biological processes at cellular and subcellular levels. For many years, these imaging techniques utilized conventional optical microscopes including those with confocal facilities. However, the spatial resolutions achieved were largely limited to around 200 nm, as determined by the diffraction of light. To overcome this diffraction barrier, considerable scientific and technological effort has resulted in the development of super-resolution optical-based techniques, scanning probe microscopies, and also techniques utilizing charged particles (e.g., energetic electrons and ions) or high-energy photons (e.g., X-ray), which exhibit much shorter de Broglie wavelengths. Among the charged particle techniques, those utilizing mega-electron-volt (MeV) ion beams appear to have unique advantages primarily because MeV ions can penetrate through several microns of biological tissue (e.g., whole cells) with little deflection in their trajectories, and hence spatial resolutions are maintained while traversing the sample. Recently, we have witnessed the significant development of MeV ion beam focusing systems in reducing beam dimensions well below 100 nm, such that single whole cell imaging at 20 nm spatial resolutions is now possible. In this review, two super resolution imaging modalities that utilize MeV highly focused ion beams are discussed: Scanning Transmission Ion Microscopy (STIM), which images the areal density of cells and gives an insight into the cellular structure, and Proton/Helium-ion Induced Fluorescence Microcopy (P/HeIFM), which images the fluorescence emission of fluorescent markers and probes used as labels within the cells. This review hopes to demonstrate the potential of MeV ion microscopy, which is still in its infancy, and describe the simultaneous use of STIM and P/HeIFM as a new and powerful multifaceted technology.

Label-free detection and manipulation of single biological nanoparticles.

In the past several years, there have been significant advances in the field of nanoparticle detection for various biological applications. Of considerable interest are synthetic nanoparticles being designed as potential drug delivery systems as well as naturally occurring or biological nanoparticles, including viruses and extracellular vesicles. Many infectious diseases and several human cancers are attributed to individual virions. Because these particles likely display different degrees of heterogeneity under normal physiological conditions, characterization of these natural nanoparticles with single-particle sensitivity is necessary for elucidating information on their basic structure and function as well as revealing novel targets for therapeutic intervention. Additionally, biodefense and point-of-care clinical testing demand ultrasensitive detection of viral pathogens particularly with high specificity. Consequently, the ability to perform label-free virus sensing has motivated the development of multiple electrical-, mechanical-, and optical-based detection techniques, some of which may even have the potential for nanoparticle sorting and multi-parametric analysis. For each technique, the challenges associated with label-free detection and measurement sensitivity are discussed as are their potential contributions for future real-world applications. WIREs Nanomed Nanobiotechnol 2016, 8:717-729. doi: 10.1002/wnan.1392 For further resources related to this article, please visit the WIREs website.

General multilayer heat transfer model for optical-based thermal characterization techniques

Optical-based techniques have been used to characterize thermal energy transport in materials for a few decades. To implement these techniques, a modulated heat source (either pulse or continuous wave) is always employed to excite a periodic temperature variation, which subsequently causes variation of temperature within the material and various other parameters that are a function of temperature. Ambient pressure, surface infrared properties, and radiation are all affected by the temperature variation and serve as indicators to indirectly detect the temperature change. To extract the properties of interest, theoretical models and solutions are necessary. In this work, we propose a general heat transfer model in multilayer structures. We also derived general solutions in the frequency domain using recursive matrix relationships. The recursive matrix simplifies the heat transfer analysis by only considering key parameters within the adjacent layers. In addition, the general analytical solution is only composed of a group of equivalent resistances that yield the contribution to the overall phase shift from each interface and can be used to directly calculate the phase difference within similar configurations. We applied this model and the associated solutions to analyze the data from the phase-sensitive transient thermoreflectance (PSTTR) technique. In contrast with typical thermoreflectance techniques, in the PSTTR technique, the pump and probe beams are applied on the opposite surfaces of the sample. We conducted PSTTR measurements on different multilayer structures, and then determined the thermal/physical properties of interest by fitting the theoretical solutions to the experimental data. The thermal conductivity of thermal grease (TC-5022) was determined to be 3.5W/(mK). Where appropriate, the fitted results were in excellent agreement with results from the literature, which validates this general model and the solution methodology. As another example of a multilayer structure, a novel direct-bonded interface that contains four layers, was studied. Its overall thermal resistance was 0.46mm2K/W, including the Al–Al contact resistance of 0.33mm2K/W and Al–Si contact resistance of 0.06mm2K/W. Using this general model along with the PSTTR technique, an in-depth understanding of the interfacial resistance was achieved by investigating the contributions from each component in the interface.

Differentiation of healthy and malignant tissue in colon cancer patients using optical spectroscopy: A tool for image-guided surgery.

Surgery for colorectal cancer aims for complete tumor resection. Optical-based techniques can identify tumor and surrounding tissue through the tissue specific optical properties, absorption and scattering, which are both influenced by the biochemical and morphological composition of the tissue. To evaluate the feasibility of dual-modality Diffuse Reflectance Spectroscopy-Fluorescence Spectroscopy (DRS-FS) for discrimination between healthy and malignant tissue in colorectal surgery. Surgical specimens from colorectal cancer patients were measured immediately after resection using a fiber-optic needle capable of dual-modality DRS-FS. Model-based analyses were used to derive scattering and absorption coefficients and intrinsic fluorescence. Volume fractions of chromophores were estimated. Furthermore, optical data were recorded along a trajectory from healthy tissue towards tumor. Spectral characteristics were identified in 1,273 measured spectra from 21 specimens. Combined DRS and FS discriminated tumor from surrounding tissue with a sensitivity of 95% and a specificity of 88%. Significant spectral changes were seen along the trajectory from healthy tissue to tumor. This study demonstrates that dual-modality DRS-FS can identify colorectal cancer from surrounding healthy tissue. The quantification of comprehensible parameters allows robust classification and facilitates extrapolation towards the clinical setting. The technique, here demonstrated in a needle like probe, can be incorporated into surgical tools for optically guided surgery in the near future. Lasers Surg. Med. 47:559-565, 2015. © 2015 Wiley Periodicals, Inc.

An electrochemical-sensor system for real-time flow measurements in porous materials.

Flow monitoring in porous materials is critical for the engineering of paper-based microfluidic bioassays. Here, we present an electrochemical-sensor system that monitors the liquid flow in porous materials without affecting the real flow in paper-strip samples. The developed microfluidic sensor records an amperometric signal created by the solution movement mediated by paper wicking. This approach allows the in situ monitoring of the different hydrodynamic conditions of a specific paper geometry or composition. In addition, the method proposed in this work was employed to characterise the fluid flow of different nitrocellulose paper strips after oxygen-plasma treatment or dextran coating. The dextran fluid-flow modifiers were further used on the paper strip-based assays as means of signal enhancement. The proposed electrochemical-sensing method offers a valuable alternative to existing optical-based monitoring techniques for flow measurement in paper-based microfluidic systems.

Experimental apparatus with full optical access for combustion experiments with laminar flames from a single circular nozzle at elevated pressures.

The design and features of a high pressure chamber and burner that is suitable for combustion experiments at elevated pressures are presented. The high pressure combustion apparatus utilizes a high pressure burner that is comprised of a chamber burner module and an easily accessible interchangeable burner module to add to its flexibility. The burner is well suited to study both premixed and non-premixed flames. The optical access to the chamber is provided through four viewports for direct visual observations and optical-based diagnostic techniques. Auxiliary features include numerous access ports and electrical connections and as a result, the combustion apparatus is also suitable to work with plasmas and liquid fuels. Images of methane flames at elevated pressures up to 25 atm and preliminary results of optical-based measurements demonstrate the suitability of the high pressure experimental apparatus for combustion experiments.

Upper limb motion tracking with the integration of IMU and Kinect

Upper limb motion tracking attracts attentions from both academia and industry due to its value in a wide range of applications. Although existing optical-based tracking techniques can provide accurate tracking results, the product cost and complexity keep them away from most daily life applications. Recently, low-cost inertial measurement unit (IMU) and Kinect techniques provide a feasible/economical solution for such trajectory tracking problems while either of them still has its own limitations. In this paper, we investigated how to fuse data from internal sensors of IMU, and fuse IMU data with Kinect in order to provide robust hand position information compensated for the limitations of those sensors. The calculation of position is sequentially achieved by three fusion strategies: double integration of IMU internal sensors, IMU internal sensor fusion with geometrical constraints and unscented Kalman filter (UKF) based fusion of IMU and Kinect. Experimental results show that the first two approaches suffer from drifting effects, while the proposed IMU and Kinect fusion method can provide drift-free and smooth results. Comparing with using Kinect alone, this approach is able to achieve better results in terms of both accuracy as well as robustness.

Multiscale Compression Entropy of Microvascular Blood FlowSignals: Comparison of Results from Laser Speckle Contrastand Laser Doppler Flowmetry Data in Healthy Subjects

Microvascular perfusion is commonly used to study the peripheral cardiovascular system. Microvascular blood flow can be continuously and non-invasively monitored with laser speckle contrast imaging (LSCI) or with laser Doppler flowmetry (LDF). These two optical-based techniques give perfusion values in arbitrary units. Our goal is to better understand the perfusion time series given by each technique. For this purpose, we propose a nonlinear complexity analysis of LSCI and LDF time series recorded simultaneously in nine healthy subjects. This is performed through the computation of their multiscale compression entropy. The results obtained with LSCI time series computed from different regions of interest (ROI) sizes are examined. Our findings show that, for LSCI and LDF time series, compression entropy values are less than one for all of the scales analyzed. This suggests that, for all scales, there are repetitive structures within the data fluctuations. Moreover, at the largest scales studied, LDF signals seem to have structures that are different from those Entropy 2014, 16 5778 of Gaussian white noise. By opposition, this is not observed for LSCI time series computed from small ROI sizes

Time to surgery and preoperative cerebral hemodynamics predict postoperative white matter injury in neonates with hypoplastic left heart syndrome

Hypoxic-ischemic white mater brain injury commonly occurs in neonates with hypoplastic left heart syndrome (HLHS). Approximately one half of HLHS survivors will exhibit neurobehavioral symptoms believed to be associated with this injury, although the exact timing of the injury is unknown. Neonates with HLHS were recruited for pre- and postoperative monitoring of cerebral oxygen saturation, cerebral oxygen extraction fraction, and cerebral blood flow using 2 noninvasive optical-based techniques: diffuse optical spectroscopy and diffuse correlation spectroscopy. Anatomic magnetic resonance imaging was performed before and approximately 1 week after surgery to quantify the extent and timing of the acquired white matter injury. The risk factors for developing new or worsened white matter injury were assessed using uni- and multivariate logistic regression. A total of 37 neonates with HLHS were studied. On univariate analysis, neonates who developed a large volume of new, or worsened, postoperative white matter injury had a significantly longer time to surgery (P=.0003). In a multivariate model, a longer time between birth and surgery, delayed sternal closure, and greater preoperative cerebral blood flow were predictors of postoperative white matter injury. Additionally, a longer time to surgery and greater preoperative cerebral blood flow on the morning of surgery correlated with lower cerebral oxygen saturation (P=.03 and P=.05, respectively) and greater oxygen extraction fraction (P=.05 for both). A longer time to surgery was associated with new postoperative white matter injury in otherwise healthy neonates with HLHS. The results suggest that earlier Norwood palliation might decrease the likelihood of acquiring postoperative white matter injury.

Optimization of circular composite patch reinforcement on damaged carbon fiber reinforced polymer laminate involving both mechanics-based and genetic algorithm in conjunction with 3D finite element analysis

Composites are significantly used in aerospace, automotive and civil structures due to their high specific strength, high stiffness, corrosion resistant and longer fatigue life. During service life, composite structures are susceptible to damage, which reduces their structural integrity. For extending its service life, the damage needs to be repaired. In case of low velocity impact damage adhesively bonded patch repair is found to be effective in extending the service life of damaged parts. The repair performance is mainly influenced by patch stacking sequence, patch shape, patch thickness, overlap length and adhesive thickness and its shear strength. In the present work, both numerical and experimental works are carried out to study the mechanics of composite patch repair on damaged carbon fiber reinforced polymer panel of configuration [45/−45/0/90]s subjected to tensile load. The influence of patch stacking sequence, patch thickness, adhesive thickness and overlap length on repair performance is investigated through a mechanics-based design approach involving finite element analysis. Stress concentration factor and shear stress in adhesive layer are considered to analyze the repair performance. Later, a genetic algorithm-based approach in conjunction with finite element analysis is implemented for arriving at an optimized patch dimension and adhesive thickness. Experimental study is then carried out with optimized geometry using non-contact optical-based technique namely digital image correlation. The strain field from digital image correlation is compared against the finite element results.