Compact Instrument Research Articles

Towards an advanced neurotechnological system: colorimetric sensing with a novel grism-based spectrometer, functionalized gold nanoparticles and a heterogeneous embedded system.

Neurotransmitter sensing in the brain is crucial for the understanding of neuro-degenerative diseases. Most modern methods for the purpose rely on bulky instruments or are disruptive to the neurotransmitter medium. In this work, we describe and evaluate the design of a novel, compact and non-invasive instrument for neurotransmitter detection based on the colorimetric sensing method. The instrument includes a grism-based spectrometer that measures the wavelength shift of gold nanoparticles that are functionalized with aptamers to act as neurotransmitter-specific markers. It also includes microfluidic and electronic subsystems for sample preparation and control, and processing of the obtained signal. The instrument is tested with gold nanoparticles and its performance is compared to that of a commercial instrument, showing that the designed prototype matches the commercial instrument in performance while being much smaller, and it can surpass it with further improvements. This article is part of the theme issue 'Advanced neurotechnologies: translating innovation for health and well-being'.

Front Cover: Online monitoring of small volume reactions using compact liquid chromatography instrumentation

DOI: 10.1002/sscp.202200012 The cover picture represents the translation of repetitive reaction mixture analysis outside a fume hood using a conventional high performance liquid chromatography stack with manual syringe sampling to online analysis inside a fume hood using a simple, compact, hand-portable capillary liquid chromatograph that can be easily placed very close to the reaction vessel. The extremely small sample volume required for analysis by capillary liquid chromatography allows the use of miniature reaction vessels with minimal disturbance of the reaction mixture.

Rover-mounted Hydrated Mineral Detector for Mars Exploration: A Preliminary Report

The rover-mounted hydrated mineral detector (HMD) is based on a dielectric spectrometer (tuned frequency range of 0.8–4 MHz) that will detect bulk subsurface hydrated minerals in local scale. The HMD is a compact, low-mass (1.5 kg), and low-power instrument (5 W) suitable for Mars application. Compared with orbiter-based instruments with low horizontal resolution (5–10 km), the HMD will offer high resolution (2 m) that can identify optimal sampling sites for the presence of hydrated minerals. From field testing with reduced radio frequency (RF) power (P rf = 10 mW), the HMD demonstrated detection of shallow buried gypsum samples. When developed with full RF power, the HMD could potentially detect hydrates down to depths of 2 m (P rf = 1 W) or 4 m (P rf = 36 W) in Martian soil. Unlike conventional dielectric spectrometers, which require small amounts of the sample (5–10 g) to be placed inside sample cells, the HMD will detect hydrated minerals by scanning over the Mars surface mounted on a rover platform (<1 m above ground) without any sample preparation. This capability will allow future rovers to rapidly assess the scientific potential of field sites. Compared with optical techniques that are limited to surface exposed mineralogical features that could be obscured by dust and weathering products, the HMD will detect bulk subsurface hydrated minerals along the rover traverse irrespective of surface obscuration. The HMD (TRL 4) is a proof-of-concept instrument that can be developed and matured for future Mars rover missions.

Psychische Gesundheit bei der Arbeit – Der psy50 als integrativer Ansatz zur Messung der Arbeitsbedingungen

Mental health at work – The psy50 as an integrative approach to the measurement of working conditions Work can either stabilize or impair mental health. Thus, factors that support well-being and commitment must be considered in addition to burdens and stressors. Further, without knowledge of the mental well-being or engagement of the workers, the assessment of psychosocial working conditions remains incomplete. Long-term studies show that the lack of or variation in resources correlates more strongly with engagement, emotional well-being or health-related productivity losses than stressors. The effects differ across personality types. Methodological advances allow the development of compact screening instruments which cover all relevant constructs yet can be completed in less than 10 minutes. The second part of the article presents such an instrument, the psy50. The instrument was developed over several years in cooperation with the BKK umbrella organization, the Federal Ministry of Labour, experts and employees as part of the psyGA project. Keywords: workplace conditions – mental health – personality – measuring psychosocial working conditions

Frequency-shifted nano-particle sizing using laser self-mixing interferometry under linear current tuning

In addition to the traditional physical quantities (such as displacement, distance, velocity and vibration) detection that has been widely researched and reported, laser self-mixing interferometry (SMI) has shown great potential in nano-particle sizing during the last two decades, primarily depending on the incoherent stochastic superposition of the laser beam’s interaction with each particle in the illuminating volume. Particle diameter can be determined from the power spectra of self-mixed signals through Lorentz fitting. SMI particle sensing using laser diodes (LDs) always adopts direct current (DC) driving, so the spectrum peak occurs around zero-frequency and merely exhibits the right-hand half. Some other particle sensors using solid-state lasers (SSLs), however, prefer to employ a pair of acousto-optic modulators (AOMs) as frequency shifters, which pronouncedly increase the complexity and the cost of the whole measurement system. In this letter, linearly injected current is applied to a LD to achieve laser frequency tuning and conveniently shift the concerned Lorentz peak to any specified spectrum position, which simplifies the measurement setup and greatly avoids the influence of DC or low-frequency disturbance. The technique proposed is beneficial to developing low-cost, compact and precise SMI particle sensors or instruments.

Comparative evaluation of methods for determining sensitivity to colistin in E. coli isolates

The study aims to compare two colistin susceptibility measurement approaches: by disk diffusion test and using VITEK® 2 Compact instrument. We collected 103 E.coli isolates from 7 livestock farms in St. Petersburg and the Leningrad region. Minimum inhibitory concentration (MIC) of colistin was determined using disk diffusion test and VITEK® 2 Compact instrument and then compared with the reference broth microdilution method results. The processing of the results was based on the EUCAST recommendations. Eight E. coli isolates proved to be resistant to colistin when determining MIC in broth microdilutions. Two isolates (eco‐103 and eco‐151) carried the MCR‐1 gene. The identical isolates were tested by other methods to determine the MIC. The data obtained by the three methods were identical. This suggests that the disc diffusion test can be used to determine the MIC of colistin on E.coli. This method has several advantages over the reference method and VITEK‐2 Compact use since it is simultaneously cheap, fast, and accurate for determining the MIC of colistin.

Compact Microfluidic Platform with LED Light-Actuated Valves for Enzyme-Linked Immunosorbent Assay Automation.

Lab-on-a-chip devices incorporating valves and pumps can perform complex assays involving multiple reagents. However, the instruments used to drive these chips are complex and bulky. In this article, a new wax valve design that uses light from a light emitting diode (LED) for both opening and closing is reported. The valves and a pumping chamber are integrated in lab-on-a-foil chips that can be fabricated at low cost using rapid prototyping techniques. A chip for the implementation of enzyme-linked immunosorbent assays (ELISA) is designed. A porous nitrocellulose material is used for the immobilization of capture antibodies in the microchannel. A compact generic instrument with an array of 64 LEDs, a linear actuator to drive the pumping chamber, and absorbance detection for a colorimetric readout of the assay is also presented. Characterization of all the components and functionalities of the platform and the designed chip demonstrate their potential for assay automation.

Feasibility of compact near-infrared spectrophotometers and multivariate data analysis to assess roasted ground coffee traits

Two low-cost, miniaturized near-infrared (NIR) spectrophotometers working in two different spectral ranges (900–1700 nm and 1300–2500 nm) and employing different spectrometric technologies were evaluated to assess several traits of ground roasted commercial coffees, using multivariate analysis. The comprehensive sample set comprised one hundred forty-five samples from different origins, blends of varietals (arabica/arabica, and arabica/robusta) or pure varietal (arabica), decaffeinated or regular, presenting several grades of sensorial traits (bitterness, intensity, acidity, body, and roast degree), as informed by the manufacturing company. Representative spectra of the samples were acquired using a probing device providing rotational and linear displacement of the sample vial. The spectral data set was evaluated using principal component analysis (PCA) models aiming to verify the discrimination capability of both instruments. When evaluated down to the fourth principal component by both compact instruments, origin, varietal, decaffeinated, and regular coffees are grouped and well-differentiated by the PCA scores. Differences among batches of the same coffee brand can be observed. Quantitative models based on partial least square (PLS) regression were evaluated to assess the feasibility of miniaturized spectrophotometers to determine the samples' intensity, bitterness, body, roast, and acidity traits. These sensorial traits can be predicted by partial least square models with root mean square errors of external validation of 1.3, 0.7, 0.6, 0.5, and 0.8 and 1.2, 0.7, 0.5, 0.5, and 0.7 for intensity, bitterness, body, roast, and acidity, respectively, using the data sets obtained by the NanoNIR, and the NeoSpectra instruments and employing variables selected by the Jack-Knife algorithm. Quantitative results can be improved using local regression models constructed with a restricted set of samples. Overall, the results reveal the potential of miniaturized, low-cost NIR spectrophotometers to characterize commercial ground roasted coffee qualitatively and quantitatively with a slight advantage of using the instrument providing the more comprehensive wavelength range and based on Fourier transform technology.

Acoustic Processing of Fluidic Samples for Planetary Exploration

The search for life on other planetary bodies is driven by our quest to determine if Earth is unique with respect to harboring life. In order to answer this question, instrumentation with suitable sensitivity is required to measure biosignatures. In addition to accurate measurements by in-situ instruments, specialized sample acquisition and sample handling hardware is required to maximize the scientific information obtained from an acquired sample. This paper discusses a class of compact sample processing instrumentation using solid-state mechanisms that use acoustic waves to process samples prior to delivery to the instrument. Some of the acoustic sample processes that can be used to aid in preparation of liquid and liquid/solid mixtures include: mixing, milling, cavitating, lysing, heating, streaming, stirring, lofting, concentrating, segregating, and filtering. We will review these acoustic processes and show how they are generated using electromechanical systems. In addition to processing, these transduction systems could also use acoustics to interrogate physical properties such as the state of the sample, the acoustic velocity, and its attenuation. In order to generate these processes and sensing capabilities at these frequencies, a transduction mechanism is required to produce stress waves from electrical signals and vice versa. One commonly used technique is to use piezoelectric transducers that generate a stress that is linearly proportional to the voltage across the transducer and a voltage that is proportional to the stress on a transducer’s face. A variety of transducer modes are available to excite the sample, including thickness, transverse, radial, and shear extensional, and these can be used to build composite resonance structures including ultrasonic horns, tuning forks, bimorph, and unimorph benders to increase stress generated in the sample. We discuss how to model the acoustic interactions with the sample and the sample chamber in order to produce the required stress waves and illustrate the use of network models of piezoelectric transducers to accomplish this modeling. We demonstrate how to build up these models using Mason’s equivalent circuit for a piezoelectric and network models for acoustic layers in a design. Finally, to illustrate this acoustic processing ability, we will discuss a few systems that we have developed for sample handling systems for other planetary bodies like Mars and ocean worlds Enceladus and Europa.

Time Domain (TD) Proton NMR Analysis of the Oxidative Safety and Quality of Lipid-Rich Foods

Food safety monitoring is highly important due to the generation of unhealthy components within many food products during harvesting, processing, storage, transportation and cooking. Current technologies for food safety analysis often require sample extraction and the modification of the complex chemical and morphological structures of foods, and are either time consuming, have insufficient component resolution or require costly and complex instrumentation. In addition to the detection of unhealthy chemical toxins and microbes, food safety needs further developments in (a) monitoring the optimal nutritional compositions in many different food categories and (b) minimizing the potential chemical changes of food components into unhealthy products at different stages from food production until digestion. Here, we review an efficient methodology for overcoming the present analytical limitations of monitoring a food’s composition, with an emphasis on oxidized food components, such as polyunsaturated fatty acids, in complex structures, including food emulsions, using compact instruments for simple real-time analysis. An intelligent low-field proton NMR as a time domain (TD) NMR relaxation sensor technology for the monitoring of T2 (spin-spin) and T1 (spin-lattice) energy relaxation times is reviewed to support decision-making by producers, retailers and consumers in regard to food safety and nutritional value during production, shipping, storage and consumption.

Online Monitoring of Small Volume Reactions Using Compact Liquid Chromatography Instrumentation.

A wide variety of analytical techniques have been employed for monitoring chemical reactions, with online instrumentation providing additional benefits compared to offline analysis. A challenge in the past for online monitoring has been placement of the monitoring instrumentation as close as possible to the reaction vessel to maximize sampling temporal resolution and preserve sample composition integrity. Furthermore, the ability to sample very small volumes from bench-scale reactions allows the use of small reaction vessels and conservation of expensive reagents. In this study, a compact capillary LC instrument was used for online monitoring of as small as 1 mL total volume of a chemical reaction mixture, with automated sampling of nL-scale volumes directly from the reaction vessel used for analysis. Analyses to demonstrate short term (~2 h) and long term (~ 50 h) reactions were conducted using tandem on-capillary ultraviolet absorbance followed by in-line MS detection or ultraviolet absorbance detection alone, respectively. For both short term and long term reactions (10 and 250 injections, respectively), sampling approaches using syringe pumps minimized the overall sample loss to ~0.2% of the total reaction volume.

A compact instrument for gamma-ray burst detection on a CubeSat platform II

The Gamma-ray Module, GMOD, is a miniaturised novel gamma-ray detector which will be the primary scientific payload on the Educational Irish Research Satellite (EIRSAT-1) 2U CubeSat mission. GMOD comprises a compact (25 mm times 25 mm times 40 mm) cerium bromide scintillator coupled to a tiled array of 4 times 4 silicon photomultipliers, with front-end readout provided by the IDE3380 SIPHRA. This paper presents the detailed GMOD design and the accommodation of the instrument within the restrictive CubeSat form factor. The electronic and mechanical interfaces are compatible with many off-the-shelf CubeSat systems and structures. The energy response of the GMOD engineering qualification model has been determined using radioactive sources, and an energy resolution of 5.4% at 662 keV has been measured. EIRSAT-1 will perform on-board processing of GMOD data. Trigger results, including light-curves and spectra, will be incorporated into the spacecraft beacon and transmitted continuously. Inexpensive hardware can be used to decode the beacon signal, making the data accessible to a wide community. GMOD will have scientific capability for the detection of gamma-ray bursts, in addition to the educational and technology demonstration goals of the EIRSAT-1 mission. The detailed design and measurements to date demonstrate the capability of GMOD in low Earth orbit, the scalability of the design for larger CubeSats and as an element of future large gamma-ray missions.

Terahertz frequency domain sensing for fast porosity measurement of pharmaceutical tablets

Porosity is an important property of pharmaceutical tablets since it may affect tablet disintegration, dissolution, and bio-availability. It is, therefore, essential to establish non-destructive, fast, and compact techniques to assess porosity, in situ, during the manufacturing process. In this paper, the terahertz frequency-domain (THz-FD) technique was explored as a fast, non-destructive, and sensitive technique for porosity measurement of pharmaceutical tablets. We studied a sample set of 69 tablets with different design factors, such as particle size of the active pharmaceutical ingredient (API), Ibuprofen, particle size of the filler, Mannitol, API concentration, and compaction force. The signal transmitted through each tablet was measured across the frequency range 500–750 GHz using a vector network analyzer combined with a quasi-optical set-up consisting of four off-axis parabolic mirrors to guide and focus the beam. We first extracted the effective refractive index of each tablet from the measured complex transmission coefficients and then translated it to porosity, using an empirical linear relation between effective refractive index and tablet density. The results show that the THz-FD technique was highly sensitive to the variations of the design factors, showing that filler particle size and compaction force had a significant impact on the effective refractive index of the tablets and, consequently, porosity. Moreover, the fragmentation behaviour of particles was observed by THz porosity measurements and was verified with scanning electron microscopy of the cross-section of tablets. In conclusion, the THz-FD technique, based on electronic solutions, allows for fast, sensitive, and non-destructive porosity measurement that opens for compact instrument systems capable of in situ sensing in tablet manufacturing.

MSI-RPi: Affordable, Portable, and Modular Multispectral Imaging Prototype Suited to Operate in UV, Visible and Mid-Infrared Regions

Digital plant inventory provides critical growth insights, given the associated data quality is good. Stable &amp; high-quality image acquisition is critical for further examination. In this work, we showcase an affordable, portable, and modular spectral camera prototype, designed with open hardware’s and open-source software’s. The image sensors used were color, and infrared Pi micro-camera. The designed prototype presents the advantage as being low-cost and modular with respect to other general commercial market available spectral devices. The micro-size connected sensors make it a compact instrument that can be used for any general spectral acquisition purposes, along with the provision of custom selection of the bands, making the presented prototype design a Plug-nd-Play (PnP) setup that can be used in different wide application areas. The images acquired from our custom-built prototype were back-tested by performing image analysis and qualitative assessments. The image acquisition software, and processing algorithm has been programmed, which is bundled with our developed system. Further, an end-to-end automation script is integrated for the users to readily leverage the services on-demand. The design files, schematics, and all the related materials of the spectral block design is open-sourced with open-hardware license &amp; is made available at https://github.com/ajayarunachalam/Multi-Spectral-Imaging-RaspberryPi-Design. The automated data acquisition scripts &amp; the spectral image analysis done is made available at https://github.com/ajayarunachalam/SI-RPi.

Development of a Low-Cost 6 DOF Brick Tracking System for Use in Advanced Gas-Cooled Reactor Model Tests.

This paper presents the design of a low-cost, compact instrumentation system to enable six degree of freedom motion tracking of acetal bricks within an experimental model of a cracked Advanced Gas-Cooled Reactor (AGR) core. The system comprises optical and inertial sensors and capitalises on the advantages offered by data fusion techniques. The optical system tracks LED indicators, allowing a brick to be accurately located even in cluttered images. The LED positions are identified using a geometrical correspondence algorithm, which was optimised to be computationally efficient for shallow movements, and complex camera distortions are corrected using a versatile Incident Ray-Tracking calibration. Then, a Perspective-Ray-based Scaled Orthographic projection with Iteration (PRSOI) algorithm is applied to each LED position to determine the six degree of freedom pose. Results from experiments show that the system achieves a low Root Mean Squared (RMS) error of 0.2296 mm in x, 0.3943 mm in y, and 0.0703 mm in z. Although providing an accurate measurement solution, the optical tracking system has a low sample rate and requires the line of sight to be maintained throughout each test. To increase the robustness, accuracy, and sampling frequency of the system, the optical system can be augmented with an Inertial Measurement Unit (IMU). This paper presents a method to integrate the optical system and IMU data by accurately timestamping data from each set of sensors and aligning the two coordinate axes. Once miniaturised, the developed system will be used to track smaller components within the AGR models that cannot be tracked with current instrumentation, expanding reactor core modelling capabilities.

Laboratory Diagnosis, Antimicrobial Susceptibility And Genuine Clinical Spectrum of Streptococcus anginosus Group; Our Experience At A University Hospital.

Background:Streptococcus anginosus group (SAG) may be unrecognized or misidentified in the Clinical Microbiology Laboratory resulting in under-reporting. Consequently, their role as genuine pathogens remains underestimated.Objectives:The aim of this study is to suggest a reasonable identification approach that is suitable for laboratories of limited resources, to detect any possible emerging antimicrobial resistance, and to assess the genuine clinical spectrum of infections that are caused solely by SAG.Methods:Our research included 190 bacterial isolates from 190 patients. The isolates were examined by colonies’ morphology, odor, hemolytic pattern on 5% sheep Blood agar and Gram staining. Lancefield serogrouping was determined by agglutination test. Antimicrobial susceptibility testing (AST) was performed by disc diffusion method. The isolates were subjected to automated identification and AST by Vitek 2 compact instrument. The collected patients’ data included age, gender, clinical condition and/or site of infection, and probable predisposing factor.Results:All isolates produced minute-sized colonies that consistently generated distinct odor. The isolates showed variable hemolytic patterns, and the majority (74.7%) were non-hemolytic. The isolates showed different Lancefield serogroups, and the commonest was group F (54.2%). A total of 188 (98.9%) isolates were identified by Vitek 2 compact instrument at ≥95% confidence. The isolates showed high rates of antimicrobial susceptibility, however the highest rate of antimicrobial resistance was detected to gentamicin (60.5%). A total of 98 (51.6%) strains were isolated from superficial non-invasive skin and soft tissue infections, 67 (35.3%) strains from deep invasive and sterile body fluids’ infections, and 25 (13.1%) strains from upper respiratory tracts’ infections.Conclusion:a combination of phenotypic characteristics could still represent a reasonable Laboratory identification battery. There was no significant emerging antimicrobial resistance detected. A broad genuine spectrum of clinical infections that are caused solely by SAG was reported in our institution.

Exploring the Implementation of Compact Chromatographic Instrumentation in Common Analytical Workflows

In many industries, the concepts of “smaller,” “faster,” “easier to use,” and “cheaper” are key drivers when developing new technologies. The world of chemical separations is no different. Today, compact chromatographic instrumentation is being implemented in many workflows, as illustrated here through various examples.

Review of Techniques for Particle Spectroscopy From DC to Terahertz Frequency

Non-destructive, contact-less, and label-free characterization of small particles plays an important role in laboratory research and industrial manufacturing. Also, the analysis of small things, especially particulate bio-matter, using electromagnetic waves has a long history in optical microscopy. Light, however, cannot reveal much information about the material property of the particle. Radio waves, on the other hand, apart from being more sensitive and featuring compact instrumentation, interact strongly with a dielectric particle. Thus, in principle, it can provide information about the particle in both shape and material. Therefore, particle spectroscopy using electrical signals plays a vital role in research and development. Although not firmly established as its optical counterpart, it is still reasonable to analyze the nascent stages of its development till now. In this review article, different state-of-art techniques for particle spectroscopy spanning from DC to terahertz frequency regime are categorized into two board domains: electromagnetic perturbation and electromagnetic scattering based approaches. A critical analysis of the uniqueness of terahertz frequency in context to particle spectroscopy is outlined. Finally, the paper discusses a realistic scaling approach from generic optical sensors to an electronic lab-on-chip design for sensing and characterization of particle-in-flow in microfluidics. It also addresses the feasibility of modern high-frequency circuit design technology for potential electromagnetic scattering-based particle spectroscopy innovations.

Compact Instrumentation for Accurate Detection and Measurement of Glucose Concentration Using Photoacoustic Spectroscopy

In this work, a novel <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">compact</i> and accurate glucose concentration measurement system is developed using the well-established photoacoustic Near Infra-Red spectroscopy. The proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-vitro</i> instrumentation methods are in a small form factor, making it a viable candidate and precursor for an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-vivo</i> non-invasive <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wearable</i> blood glucose monitoring in the near future. The accuracy comes from the phase sensitive detection of the electrical signal. This detection technique uses an off-the shelf modulator/demodulator integrated circuit configured as a lock-in amplifier to increase the signal to noise ratio multifold. No prior work on photoacoustic spectroscopy, has taken advantage of this detection methodology in such a small form factor. The dimension of the lock-in-amplifier is 13mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$ </tex-math></inline-formula> 10.65mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$ </tex-math></inline-formula> 2.65mm. The maximum linear dimension of the exciting laser is 5.6 mm. The acoustic sensor (transducer) has a dimension of 42mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$ </tex-math></inline-formula> 12mm. Furthermore, the measurement and analyses of the observed data uses multiple stochastic and machine learning techniques to bring out the best correlation fit between the glucose concentration and a specific feature of the electrical signal. With these methods and techniques, a strong correlation was confirmed between the glucose concentration and the amplitude of the electrical signal. The computed correlation coefficient between the signal amplitude and glucose concentration is 97% while the p-value is 5.6E-6. To the best of our knowledge, this is the first work to report photoacoustic spectroscopy for glucose concentration measurement in a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">compact</i> form, with lock-in amplifier and aided with machine learning algorithms for future application as a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wearable</i> device.

Mobile and high-spectral-resolution Fabry–Pérot interferometer spectrographs for atmospheric remote sensing

Abstract. Grating spectrographs (GS) are presently widely in use for atmospheric trace gas remote sensing in the ultraviolet (UV) and visible spectral range (e.g. differential optical absorption spectroscopy, DOAS). For typical DOAS applications, GSs have a spectral resolution of about 0.5 nm, corresponding to a resolving power R (ratio of operating wavelength to spectral resolution) of approximately 1000. This is sufficient to quantify the vibro-electronic spectral structure of the absorption of many trace gases with good accuracy and further allows for mobile (i.e. compact and stable) instrumentation. However, a much higher resolving power (R≈105, i.e. a spectral resolution of about the width of an individual rotational absorption line) would facilitate the measurement of further trace gases (e.g. OH radicals), significantly reduce cross interferences due to other absorption and scattering processes, and provide enhanced sensitivity. Despite these major advantages, only very few atmospheric studies with high-resolution GSs are reported, mostly because increasing the resolving power of a GS leads to largely reduced light throughput and mobility. However, for many environmental studies, light throughput and mobility of measurement equipment are central limiting factors, for instance when absorption spectroscopy is applied to quantify reactive trace gases in remote areas (e.g. volcanoes) or from airborne or space-borne platforms. For more than a century, Fabry–Pérot interferometers (FPIs) have been successfully used for high-resolution spectroscopy in many scientific fields where they are known for their superior light throughput. However, except for a few studies, FPIs have hardly received any attention in atmospheric trace gas remote sensing, despite their advantages. We propose different high-resolution FPI spectrograph implementations and compare their light throughput and mobility to GSs with the same resolving power. We find that nowadays mobile high-resolution FPI spectrographs can have a more than 2 orders of magnitude higher light throughput than their immobile high-resolution GS counterparts. Compared with moderate-resolution GSs (as routinely used for DOAS), an FPI spectrograph reaches a 250 times higher spectral resolution while the signal-to-noise ratio (SNR) is reduced by only a factor of 10. Using a first compact prototype of a high-resolution FPI spectrograph (R≈148 000, &lt;8 L, &lt;5 kg), we demonstrate that these expectations are realistic. Using mobile and high-resolution FPI spectrographs could have a large impact on atmospheric near-UV to near-infrared (NIR) remote sensing. Applications include the enhancement of the sensitivity and selectivity of absorption measurements of many atmospheric trace gases and their isotopologues, the direct quantification of OH radicals in the troposphere, high-resolution O2 measurements for radiative transfer and aerosol studies, and solar-induced chlorophyll fluorescence quantification using Fraunhofer lines.