Miniature Spectrometer Research Articles

Spectroscopic and Imaging Characteristics of Pigmented Non-Melanoma Skin Cancer and Melanoma in Patients with Skin Phototypes III and IV.

IntroductionNon-melanoma skin cancer is the most common malignancy worldwide. Differentiating between malignant and benign skin tumors, however, can be challenging. As a result, various auxiliary tools have been developed to aid in the diagnosis of cutaneous neoplasms. Here, skin tumors were investigated through analysis of their digital image histograms and spectroscopic response under ultraviolet (UV) and white light-emitting diodes (LEDs).MethodsFifty tumoral lesions were spectroscopically and histologically studied. For optical studies, UV at 375 nm and white LEDs were used to illuminate the lesions. Commercial cameras were used for imaging, and a miniature spectrometer with a bifurcated optical fiber was used for spectroscopic measurements.ResultsIn this study, the intensity histograms of the images taken under white and UV illumination and the spectroscopic response under white light showed clear differences between pigmented basal cell carcinoma (BCC), intradermal melanocytic nevus (IDN), and melanoma lesions for skin phototypes III and IV. However, there was little difference in their spectroscopic response to the UV LED.ConclusionWe found differences in the intensity and shape of diffuse reflectance spectra of pigmented BCC, IDN, and melanoma lesions in patients with skin phototypes III and IV. Also, images taken under UV and white light were helpful for differentiation of these pigmented lesions. Additional research is needed to ascertain the clinical utility of these tools for skin cancer diagnosis.

Colonization of Snow by Microorganisms as Revealed Using Miniature Raman Spectrometers-Possibilities for Detecting Carotenoids of Psychrophiles on Mars?

We tested the potential of a miniaturized Raman spectrometer for use in field detection of snow algae pigments. A miniature Raman spectrometer, equipped with an excitation laser at 532 nm, allowed for the detection of carotenoids in cells of Chloromonas nivalis and Chlamydomonas nivalis at different stages of their life cycle. Astaxanthin, the major photoprotective pigment, was detected in algal blooms originating in snows at two alpine European sites that differed in altitude (Krkonoše Mts., Czech Republic, 1502 m a.s.l., and Ötztal Alps, Austria, 2790 m a.s.l.). Comparison is made with a common microalga exclusively producing astaxanthin (Haematococcus pluvialis). The handheld Raman spectrometer is a useful tool for fast and direct field estimations of the presence of carotenoids (mainly astaxanthin) within blooms of snow algae. Application of miniature Raman instruments as well as flight prototypes in areas where microbes are surviving under extreme conditions is an important stage in preparation for successful deployment of this kind of instrumentation in the framework of forthcoming astrobiological missions to Mars. Key Words: Snow algae-Chloromonas nivalis-Chlamydomonas nivalis-On-site field detection-Raman spectroscopy-Astaxanthin. Astrobiology 16, 913-924.

Miniature nuclear magnetic resonance spectrometer using a partially enclosed permanent magnet

ABSTRACTConventional nuclear magnetic resonance (NMR) instruments are limited by their large volume volume. A miniature NMR spectrometer is reported using a partially enclosed miniature permanent magnet and a low-cost solenoid microcoil probe. The miniature NMR spectrometer uses a sample volume smaller than conventional NMR spectrometers by a factor of 1000. Transverse relaxation times were obtained by the miniature spectrometer using 150 nL of 40 mM copper sulfate, 1 M aqueous sucrose, absolute ethanol, and deionized water. The results demonstrate that high signal-to-noise ratios were obtained. The results were also compared with a commercial NMR spectrometer and suitable accuracy of the laboratory-constructed device was obtained. The miniature NMR spectrometer was employed for the characterization of heated soybean oil. The reported miniature NMR spectrometer is anticipated to have applications for onsite detection.

Real-Time, Online Automated System for Measurement of Water-Soluble Reactive Phosphate Ions in Atmospheric Particles.

We present a novel automated system for real-time measurements of water-soluble reactive phosphate (SRP) ions in atmospheric particles. Detection of SRP is based on molybdenum blue chemistry with Sn(II) chloride dihydrate reduction. The instrumentation consists of one particle-into-liquid sampler (PILS) coupled with a 250 cm path length liquid waveguide capillary cell (LWCC) and miniature fiber optic spectrometer, with detection wavelength set at 690 nm. The detection limit was 0.4 nM P, equivalent to 0.03 nmol P m(-3) in atmospheric particles. Comparison of SRP in collocate PM2.5 aerosol filter sampling with the PILS-LWCC on line system were in good agreement (n = 49, slope = 0.84, R(2) = 0.78). This novel technique offers at least an order of magnitude enhancement in sensitivity over existing approaches allowing for SRP measurements of unprecedented frequency (8 min), which will lead to greater understanding of the sources and impacts of SRP in atmospheric chemistry.

MEMS type ionization vacuum sensor

The paper presents the first MEMS type ionization vacuum sensor corresponding to the classical gauges with cold cathodes. In contrast to the other MEMS sensors, it works both in medium and high vacuum. It covers a pressure range from 20 down to 10−4Pa. The sensor is made of silicon and glass substrates by the use of microengineering techniques. The overall dimensions of the sensor are 20×12×10mm3. It operates on the principle of ionization of gases in an electric discharge, similarly to the Penning gauge. The value of the discharge current is a measure of pressure. The sensor can also be used for residual gas composition analysis in pressure range from 1000Pa to 10−1Pa. The composition of gas species is determined on the basis of spectra of the glowing gases, recorded by a miniature fiber spectrometer. Properties of the sensor: relations between discharge current, pressure, and power supply conditions, as well as characteristic spectral lines have been measured in a reference vacuum chamber for air and several gases.

Fabrication of a concave grating with a large line spacing via a novel dual-beam interference lithography method.

We introduce a novel dual-beam interference lithography (IL) method that makes it possible to fabricate a concave grating with a large line spacing. A concave lens is placed between two point sources for spatial interference and a concave substrate to produce the grating pattern. The original positions of the two point sources are separated by the concave lens, which permits the IL method to fabricate a concave grating that bypasses the line spacing limitation of the conventional IL system. A concave grating with a line spacing of about 3.8 μm was fabricated and fitted inside a miniature spectrometer. The enlarged line spacing reduces the detector length by 66.5%, while keeping the resolution better than 1.5 nm over a wide spectral band (360 - 825 nm).

A simple spectroscopic method to determine the degree of dissociation in hydrogen plasmas with wide-range spectrometer.

A new and simple method for determining the degree of dissociation in hydrogen plasmas is presented. In this method, wide-range spectrum covering from an atomic H-γ line (434.05 nm) to molecular Fulcher-α band (600-640 nm) is measured simultaneously by a wide-range miniature spectrometer. Since the wide-range spectrum measured by the miniature spectrometer is too broadened to resolve respective lines in the Fulcher-α band, a synthetic spectrum method is applied to improve the accuracy in the Q-branch of Fulcher-α band intensity measurement. In order to reduce the influence from other transitions or anomalous P- and R-branch of Fulcher-α spectrum, the Fulcher-α spectra of which vibrational states are higher than 1 (υ ≥ 1) are synthesized using the rotational temperature obtained by the 0-0 Fulcher-α spectrum. The degree of dissociation is determined from the intensity ratio between H-γ line and the synthesized Fulcher-α band spectrum. A comparative study carried out in a volume-produced negative hydrogen ion source shows that the degree of dissociation determined by this method agrees well with the measured values using a spectrometer with high spectral resolution. The present method is expected to be useful to characterize the plasma sources with molecular species since it provides important parameters for understanding neutral particle behaviors.

Enhancing Sensitivity of a Miniature Spectrometer Using a Real-Time Image Processing Algorithm.

A real-time image processing algorithm is developed to enhance the sensitivity of a planar single-mode waveguide miniature spectrometer with integrated waveguide gratings. A novel approach of averaging along the arcs in a curved coordinate system is introduced which allows for collecting more light, thereby enhancing the sensitivity. The algorithm is tested using CdSeS/ZnS quantum dots drop casted on the surface of a single-mode waveguide. Measurements indicate that a monolayer of quantum dots is expected to produce guided mode attenuation approximately 11 times above the noise level.

Miniature X-Ray Solar Spectrometer: A Science-Oriented, University 3U CubeSat

The miniature x-ray solar spectrometer is a three-unit CubeSat developed at the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder. Over 40 students contributed to the project with professional mentorship and technical contributions from professors in the Aerospace Engineering Sciences Department at University of Colorado, Boulder and from Laboratory for Atmospheric and Space Physics scientists and engineers. The scientific objective of the miniature x-ray solar spectrometer is to study processes in the dynamic sun, from quiet sun to solar flares, and to further understand how these changes in the sun influence the Earth’s atmosphere by providing unique spectral measurements of solar soft x rays. The enabling technology providing the advanced solar soft x-ray spectral measurements is the Amptek X123, a commercial off-the-shelf silicon drift detector. The Amptek X123 has a low mass ( after modification), modest power consumption (), and small volume (), making it ideal for a CubeSat. This paper provides an overview of the miniature x-ray solar spectrometer mission: the science objectives, project history, subsystems, and lessons learned, which can be useful for the small-satellite community.

Smartphone Optosensing Platform Using a DVD Grating to Detect Neurotoxins

We present a smartphone optosensing platform (SOP) using a digital versatile disc (DVD) diffraction grating for rapid in-field detecting neurotoxins. The smartphone holder and sample holder were 3D printed for the SOP. A DVD grating is demonstrated for the first time in a low-cost miniature spectrometer on the SOP to quantify the concentrations of neurotoxins. The SOP is capable of detecting optical absorbance spectra within the entire visible spectral range from 400 to 700 nm with the spectral resolution of 0.2521 nm/pixel. We demonstrated the performance of the DVD grating compared with a commercial transmission grating on the SOP and a conventional microplate reader. Paraoxon, as the selected neurotoxin model, is assayed by two types of cholinesterase (ChE) on our SOP, respectively. Integrating a DVD grating in the SOP allows quantification of paraoxon in the range from 5 nM to 25 μM with the detection limit of 2.9 nM. In addition to the low assessed detection limit at medically relevant concentrations...

Holographic fabrication of large-constant concave gratings for wide-range flat-field spectrometers with the addition of a concave lens.

We present a new design for the fabrication of concave gratings with large grating constants for flat-field miniature spectrometers with a wide spectral band. In this new design, one of the two optical paths for the holographic lithography of a curved grating structure with variable line spacing is modified by adding a concave lens in front of the point source. The addition of the concave lens allows the real point source, as well as the spatial filter for generating this point source, to be moved back. In this manner, the two spatial filters for generating two point sources are separated. Avoiding the physical conflict between these two spatial filters reduces the difficulty of fabricating large-constant concave gratings. Experimental results verify the feasibility of the proposed design in fabricating concave gratings with large grating constants. The resolution of a spectrometer using the fabricated concave grating is evaluated and found to be better than 1.1 nm across a spectral band ranging from 360 nm to 825 nm.

Improving the spectral resolution of flat-field concave grating miniature spectrometers by dividing a wide spectral band into two narrow ones

In this study, a new flat-field concave grating miniature spectrometer is proposed with improved resolution across a wide spectral band. A mirror is added to a conventional concave grating spectrometer and placed near the existing detector array, allowing a wide spectral band to be divided into two adjacent subspectral bands. One of these bands is directly detected by the detector, and the other is indirectly analyzed by the same detector after being reflected by the mirror. These two subspectral bands share the same entrance slit, concave grating, and detector, which allows for a compact size, while maintaining an improved spectral resolution across the entire spectral band. The positions of the mirror and other parameters of the spectrometer are designed by a computer procedure and the optical design software ZEMAX. Simulation results show that the resolution of this kind of flat-field concave grating miniature spectrometer is better than 1.6 nm across a spectral band of 700 nm. Experiments based on three laser sources reveal that the measured resolutions are comparable to the simulated ones, with a maximum relative error between them of less than 19%.

The optical, electrical, and nanomechanical properties of ZnO thin films

In this experiment, ZnO thin films were sputtered on a glass substrate by a radio frequency (RF) magnetron sputtering system at room temperature (RT). The thicknesses (tf) of the ZnO thin film were from 500Å to 1000Å. X-ray diffraction (XRD), ultra miniature spectrometer (Spactra Smart) and four-point probe measurements were used to investigate the characteristics of ZnO thin film with various thicknesses. The results exhibited that ZnO has a wurtzite structure with a (002) texture diffraction peak in the 2θ at 34° range. As the ZnO thin film thickness increases, the grain size becomes larger. A ZnO thin film thickness of 500Å had a transmittance maximum of about 85% and a reflectance minimum of about 15%. That means that thickness and crystallinity of ZnO play an important role in the optical results. Additionally, the four-point probe measuring resistivity (ρ) found that the ρ is reduced as the ZnO thickness increases because grain boundaries and the surface of thin films scatter the electrons, so thinner films have a greater resistance. Between grain size and the nanoindentation results, the decline in the hardness and Young's modulus can be reasonably concluded to be associated with an enlarged grain size, consistent with the “Hall–Petch” effect and the grain refinement mechanism. Based on the optical, electrical, and nanomechanical results, a thickness of 500Å of ZnO is suitable for photoelectrical application.

On the use of laser induced breakdown spectroscopy to characterize the naturally existing crystal in Pakistan and its optical emission spectrum

We have used the Laser Induced Breakdown Spectroscopic (LIBS) technique to qualitatively identify the naturally existing transparent crystal as a pure quartz (SiO2) by observing its optical emission spectra using a Q-switched Nd:YAG laser, fundamental wavelength at 1064nm and second harmonic at 532nm. The spectra were registered using a set of five miniature spectrometers covering the spectral range from 200nm to 720nm. The plasma temperature has been calculated in the range from 8500K to 10,200K and the electron densities determined from the Stark broadened spectral lines in the range of 1.0×1017cm−3 to 6.0×1017cm−3. We report here the full widths at maximum of the spectral lines associated with the 3p4s 3P0,1,2→3p23P0,1,2, 1S0, 1D2 transitions in Si and four multiplets of singly ionized silicon.

Evaluation of Dielectric Properties of HTCC Alumina for Realization of Plasma Sources

The prospect of finding life outside Earth has fascinated mankind for ages, and new technology continuously pushes the boundary of how remote and how obscure evidence we can find. Employing smaller, or completely new, types of landers and robots, and equipping them with miniature instruments would indeed revolutionize exploration of other planets and moons.In this thesis, microsystems technology is used to create a miniature high-precision isotope-resolving molecular spectrometer utilizing the optogalvanic effect. The heart of the instrument, as well as this thesis, is a microplasma source.The plasma source is a split-ring resonator, chosen for its simplicity, pressure range and easily accessible plasma, and modified to fit the challenging application, e.g., by the adding of an additional ground plane for improved electromagnetic shielding, and the integration of microscopic plasma probes to extract the pristine optogalvanic signal.Plasma sources of this kind have been manufactured in both printed circuit board and alumina, the latter for its chemical inertness and for compatibility with other devices in a total analysis system. From previous studies, classical optogalvanic spectroscopy (OGS), although being very sensitive, is known to suffer from stability and reproducibility issues. In this thesis several studies were conducted to investigate and improve these shortcomings, and to improve the signal-to-noise ratio. Moreover, extensive work was put into understanding the underlying physics of the technique.The plasma sources developed here, are the first ever miniature devices to be used in OGS, and exhibits several benefits compared to traditional solutions. Furthermore, it has been confirmed that OGS scales well with miniaturization. For example, the signal strength does not decrease as the volume is reduced like in regular absorption spectroscopy. Moreover, the stability and reproducibility are greatly increased, in some cases as much as by two orders of magnitude, compared with recent studies made on a classical OGS setup. The signal-to-noise ratio has also been greatly improved, e.g., by enclosing the sample cell and by biasing the plasma. Another benefit of a miniature sample cell is the miniscule amount of sample it requires, which can be important in many applications where only small amounts of sample are available.To conclude: With this work, an important step toward a miniature, yet highly performing, instrument for detection of extraterrestrial life, has been taken.

Discrimination of Breast Cancer from Normal Tissue with Raman Spectroscopy and Chemometrics

Conventional Raman spectra of normal and cancerous breast tissues were acquired at an excitation wavelength of 785 nm and subjected to a discrimination analysis. First the spectra were pretreated with wavelet transform and polynomial fitting; next, cancerous tissue was identified by applying an adaptive local hyperplane K-nearest neighbor (ALHK) method to the pretreated spectra. The best discrimination accuracy of the ALHK method was 93.2%. In summary, normal and cancerous breast tissue were accurately distinguished by a miniature laser Raman spectrometer and the chemometrics method (ALHK), which might prove to be a portable and accessible diagnostic system.

Miniature spectrometer based on diffraction in a dispersive hole array.

We present an ultra-compact spectrometer that uses a 10×10 hole array as the dispersive component. Our analysis shows that the two-dimensional intensity distribution can be modeled by a system of simultaneous linear equations when the size of each hole in the dispersive component has been pre-designed appropriately. One can readily recover the spectral contents of the input radiation by solving the linear equation system with regularized procedure. Experimental results show that the reconstruction range is at least within the entire visible band, which can be further extended if a near-infrared CCD is used. One therefore envisions strong potential for many wavelength analysis applications.

An online peak extraction algorithm for ion mobility spectrometry data

Ion mobility (IM) spectrometry (IMS), coupled with multi-capillary columns (MCCs), has been gaining importance for biotechnological and medical applications because of its ability to detect and quantify volatile organic compounds (VOC) at low concentrations in the air or in exhaled breath at ambient pressure and temperature. Ongoing miniaturization of spectrometers creates the need for reliable data analysis on-the-fly in small embedded low-power devices. We present the first fully automated online peak extraction method for MCC/IMS measurements consisting of several thousand individual spectra. Each individual spectrum is processed as it arrives, removing the need to store the measurement before starting the analysis, as is currently the state of the art. Thus the analysis device can be an inexpensive low-power system such as the Raspberry Pi.The key idea is to extract one-dimensional peak models (with four parameters) from each spectrum and then merge these into peak chains and finally two-dimensional peak models. We describe the different algorithmic steps in detail and evaluate the online method against state-of-the-art peak extraction methods.

Correcting temperature dependence in miniature spectrometers used in cold polar environments.

Measurement biases arising from changes in temperature can be a major concern when using miniature spectrometers in extreme environments, particularly when temperature stabilization approaches are not feasible. Here, temperature-related biases of a low-power field spectrometry system comprised of a CMOS miniature monolithic spectrometer module and custom driver electronics were examined between -40°C and +25.6°C, well below the stated operating range of this particular spectrometer. Using these observations, a predictive model was developed to estimate the dark output of the spectrometry system within this extended operating range. This information was used to correct the signal at any measured integration time and temperature to that which would be measured at a reference integration time and temperature. This approach provides a general framework for assessing the temperature dependence of monolithic spectrometers whose field use will occur at temperatures outside of the range examined by the manufacturer.

Miniature fiber optic spectrometer-based quantitative fluorescence resonance energy transfer measurement in single living cells.

Spectral measurement of fluorescence resonance energy transfer (FRET), spFRET, is a widely used FRET quantification method in living cells today. We set up a spectrometer-microscope platform that consists of a miniature fiber optic spectrometer and a widefield fluorescence microscope for the spectral measurement of absolute FRET efficiency (E) and acceptor-to-donor concentration ratio (R(C)) in single living cells. The microscope was used for guiding cells and the spectra were simultaneously detected by the miniature fiber optic spectrometer. Moreover, our platform has independent excitation and emission controllers, so different excitations can share the same emission channel. In addition, we developed a modified spectral FRET quantification method (mlux-FRET) for the multiple donors and multiple acceptors FRET construct (mD∼nA) sample, and we also developed a spectra-based 2-channel acceptor-sensitized FRET quantification method (spE-FRET). We implemented these modified FRET quantification methods on our platform to measure the absolute E and R(C) values of tandem constructs with different acceptor/donor stoichiometries in single living Huh-7 cells.