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1.
Sensors (Basel) ; 21(24)2021 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-34960527

RESUMO

We developed a novel miniature micro-lensed fibre probe for Raman spectroscopy. The fibre probe consists of a single negative-curvature fibre (NCF) and a spliced, cleaved, micro-lensed fibre cap. Using a single NCF, we minimized the Raman background generated from the silica and maintained the diameter of the probe at less than 0.5 mm. In addition, the cap provided fibre closure by blocking the sample from entering the hollow parts of the fibre, enabling the use of the probe in in vivo applications. Moreover, the micro-lensed cap offered an improved collection efficiency (1.5-times increase) compared to a cleaved end-cap. The sensing capabilities of the micro-lensed probe were demonstrated by measuring different concentrations of glucose in aqueous solutions.


Assuntos
Lentes , Análise Espectral Raman , Desenho de Equipamento , Dióxido de Silício
2.
Sensors (Basel) ; 21(21)2021 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-34770658

RESUMO

The successful development of a system realizing color sonification would enable auditory representation of the visual environment. The primary beneficiary of such a system would be people that cannot directly access visual information-the visually impaired community. Despite the plethora of sensory substitution devices, developing systems that provide intuitive color sonification remains a challenge. This paper presents design considerations, development, and the usability audit of a sensory substitution device that converts spatial color information into soundscapes. The implemented wearable system uses a dedicated color space and continuously generates natural, spatialized sounds based on the information acquired from a camera. We developed two head-mounted prototype devices and two graphical user interface (GUI) versions. The first GUI is dedicated to researchers, and the second has been designed to be easily accessible for visually impaired persons. Finally, we ran fundamental usability tests to evaluate the new spatial color sonification algorithm and to compare the two prototypes. Furthermore, we propose recommendations for the development of the next iteration of the system.


Assuntos
Pessoas com Deficiência Visual , Dispositivos Eletrônicos Vestíveis , Algoritmos , Humanos , Som
3.
Opt Express ; 29(3): 3764-3771, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33770969

RESUMO

We present a Mach-Zehnder interferometer assisted ring resonator configuration (MARC) to realize resonator transmission spectra with unique spectral signatures and significantly large effective free spectral ranges. Transmission spectra with unique spectral signatures are generated by changing the angular separation between the through port and the drop port waveguides of the ring resonator (RR). These spectral signatures are comprised of several distinct resonance lineshapes including Lorentzian, inverse Lorentzian and asymmetric Fano-like shapes. One of the spectral signatures generated from the MARC device is utilized for the temperature sensing measurement to demonstrate a MARC-based sensor with high Q-factor and wide measurement range.

4.
J Biophotonics ; 14(5): e202000450, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33583135

RESUMO

Near infrared spectroscopy (NIR) is a promising technique for continuous blood glucose monitoring for diabetic patients. Four interferents, at physiological concentrations, were introduced to study how the glucose predictions varied with a standard multivariate calibration model. Lactate and ethanol were found to interfere strongly with the glucose predictions unless they were included in the calibration models. Lactate was mistaken for glucose and gave erroneously high glucose predictions, with a dose response of 0.46 mM/mM. The presence of ethanol resulted in too low glucose predictions, with a dose response of -0.43 mM/mM. Acetaminophen, a known interferent in the glucose monitoring devices used for diabetes management today, was not found to be an interferent in NIR spectroscopy, nor was caffeine. Thus, interferents that may appear in high concentrations, such as ethanol and lactate, must be included in the calibration or model building of future NIR-based glucose measurement devices for diabetes monitoring.


Assuntos
Glicemia , Espectroscopia de Luz Próxima ao Infravermelho , Automonitorização da Glicemia , Calibragem , Glucose , Humanos , Análise dos Mínimos Quadrados
5.
Biomed Opt Express ; 11(7): 3818-3829, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-33014568

RESUMO

Fast and accurate continuous glucose monitoring is needed in future systems for control of blood glucose levels in type 1 diabetes patients. Direct spectroscopic measurement of glucose in the peritoneal cavity is an attractive alternative to conventional electrochemical sensors placed subcutaneously. We demonstrate the feasibility of fast glucose measurements in peritoneal fluid using a fibre-coupled tuneable mid-infrared quantum cascade laser. Mid-infrared spectra (1200-925 cm-1) of peritoneal fluid samples from pigs with physiological glucose levels (32-426 mg/dL, or 1.8-23.7 mmol/L) were acquired with a tuneable quantum cascade laser employing both transmission and attenuated total reflection (ATR) spectroscopy. Using partial least-squares regression, glucose concentrations were predicted with mean absolute percentage errors (MAPEs) of 8.7% and 12.2% in the transmission and ATR configurations, respectively. These results show that highly accurate concentration predictions are possible with mid-infrared spectroscopy of peritoneal fluid, and represent a first step towards a miniaturised optical sensor for intraperitoneal continuous glucose monitoring.

7.
MethodsX ; 6: 2584-2591, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31763190

RESUMO

During the process of converting the organic matter into methane, many volatile fatty acids (VFAs) are produced during acidogenesis and acetogenesis phases of the process. The main VFAs of interest are acetic acid, butyric acid and propionic acid. Although the production of these VFAs are essential for the production of methane, they also play an inhibitory role for many of the organisms involved in the production of biogas. As a consequence, the levels of VFAs produced in an anaerobic digester must be monitored. Current methodologies for VFA monitoring are either unspecific, or costly. Therefore, the development of a sensor method that is specific to the different VFAs, while maintaining a low cost, will facilitate the lowering of biogas production, as well as avoiding the costly biological collapse of the whole biogas production process. Here, an array of coloured dyes (colourimetric array) has been assessed for their ability to detect low concentrations of VFAs within the digestate during biogas production. This methodology lays the foundation for the development of a sensor system for use in biogas plants and could also be expanded to detect many other parameters within the biogas production process. •Easy to establish.•Low user input.•Accurate measurement.

8.
Sensors (Basel) ; 19(23)2019 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-31771133

RESUMO

The development of rapid and accurate biomedical laser spectroscopy systems in the mid-infrared has been enabled by the commercial availability of external-cavity quantum cascade lasers (EC-QCLs). EC-QCLs are a preferable alternative to benchtop instruments such as Fourier transform infrared spectrometers for sensor development as they are small and have high spectral power density. They also allow for the investigation of multiple analytes due to their broad tuneability and through the use of multivariate analysis. This article presents an in vitro investigation with two fiber-coupled measurement setups based on attenuated total reflection spectroscopy and direct transmission spectroscopy for sensing. A pulsed EC-QCL (1200-900 cm - 1 ) was used for measurements of glucose and albumin in aqueous solutions, with lactate and urea as interferents. This analyte composition was chosen as an example of a complex aqueous solution with relevance for biomedical sensors. Glucose concentrations were determined in both setup types with root-mean-square error of cross-validation (RMSECV) of less than 20 mg/dL using partial least-squares (PLS) regression. These results demonstrate accurate analyte measurements, and are promising for further development of fiber-coupled, miniaturised in vivo sensors based on mid-infrared spectroscopy.


Assuntos
Espectrofotometria Infravermelho/métodos , Glucose/química , Ácido Láctico/química , Lasers Semicondutores , Análise dos Mínimos Quadrados , Miniaturização/métodos , Análise Multivariada , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Água/química
9.
Sensors (Basel) ; 19(18)2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31540533

RESUMO

Fabrication of multimode fiber optic interferometers requires accurate control of certain parameters to obtain reproducible results. This paper evaluates the consequences of practical challenges in fabricating reflection-based, fiber optic interferometers by the use of theory and experiments. A guided-mode propagation approach is used to investigate the effect of the end-face cleave angle and the accuracy of the splice in core-mismatched fiber optic sensors. Cleave angles from high-end fiber cleavers give differences in optical path lengths approaching the wavelength close to the circumference of the fiber, and the core-mismatched splice decides the ensemble of cladding modes excited. This investigation shows that the cleave angle may significantly alter the spectrum, whereas the splice is more robust. It is found that the interferometric visibility can be decreased by up to 70% for cleave angles typically obtained. An offset splice may reduce the visibility, but for offsets experienced experimentally the effect is negligible. An angled splice is found not to affect the visibility but causes a lower overall intensity in the spectrum. The sensitivity to the interferometer length is estimated to 60 nm/mm, which means that a 17 µm difference in length will shift the spectrum 1 nm. Comparisons to experimental results indicate that the spliced region also plays a significant role in the resulting spectrum.

10.
Med Hypotheses ; 132: 109318, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31421420

RESUMO

The artificial pancreas requires fast and reliable glucose measurements. The peritoneal space has shown promising results, and in one of our studies we detected glucose changes in the peritoneal space already at the same time as in the femoral artery. The peritoneal lining is highly vascularised, covered by a single layer of mesothelial cells and therefore easily accessible for proper sensor technology, e.g. optical technology. We hypothesize that the rapid intraperitoneal glucose dynamics observed in our study was possible because the sensors were located directly at the peritoneal lining, at the point where the glucose molecules entered the peritoneal space. Glucose travels slowly in fluids by diffusion, and a longer distance between the sensor and the peritoneal lining would consequently result in slower dynamics. We therefore propose to place the glucose sensor in an artificial pancreas as closely to the peritoneal lining as possible, or even utilize appropriate sensor technology to measure glucose in the peritoneal lining itself.


Assuntos
Diabetes Mellitus Tipo 1/sangue , Diabetes Mellitus Tipo 1/terapia , Glucose/análise , Pâncreas Artificial , Diálise Peritoneal/métodos , Peritônio/irrigação sanguínea , Peritônio/metabolismo , Animais , Técnicas Biossensoriais , Difusão , Epitélio , Desenho de Equipamento , Artéria Femoral/metabolismo , Humanos , Dispositivos Ópticos , Suínos
11.
Ultrason Sonochem ; 58: 104675, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31450307

RESUMO

The global demand for non-fossil energy sources is increasing rapidly. As a result, biogas presents a suitable alternative; however, first generation biofuels (e.g., sugar cane) potentially impact food crops globally. Second generation biofuels based on lignocellulose-based biomass are being used more frequently as they do not impact food crops. Furthermore, in Northern Europe, there is a significant interest in utilizing birchwood and paper mill waste for biogas production due to its high availability. The utilization of birchwood for biogas has significantly improved in recent years with the improvement of required pretreatment processes. To date, the most effective and economically feasible pretreatment in an industrial context is the steam explosion of lignocellulose-based biomass. Despite this, there is potential for releasing more digestible components from this biomass by efficiently degrading the lignocellulose components. This research presents another pretreatment that can be applied to steam-exploded wood based on ultrasonication and Fenton reagents. It was observed that by treating the steam exploded birchwood with ultrasonication and mild concentrations of Fenton reagents, an increase in the rate of biogas production was achievable. This would allow the increase in biogas yield of a continuously feed industrial anaerobic digester without increasing the size of the reactor.

12.
Eng Life Sci ; 19(11): 759-769, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32624969

RESUMO

Biogas production is becoming significantly viable as an energy source for replacing fossil-based fuels. The further development of the biogas production process could lead to significant improvements in its potential. Wastewater treatment currently accounts for 3% of the electrical energy load in developed countries, while it could be developed to provide a source of nitrogen and phosphorus, in addition to energy. The improvement of anaerobic digestion (AD) detection technologies is the cornerstone to reach higher methane productivities and develop fully automatized processes to decrease operational costs. New sensors are requested to automatically obtain a better interpretation of the complex and dynamical internal reactor environment. This will require detailed systematic detection in order to realize a near-optimal production process. In this review, optical fiber-based sensors will be discussed to assess their potential for use in AD. There is currently a disparity between the complexity of AD, and online detection. By improving the durability, sensitivity, and cost of dissolved H2 (as well as H2S, acetic acid, ammonia, and methane) sensor technology, further understanding of the AD process may allow the prevention of process failure. The emergence of surface plasmon resonance (SPR) sensing with optical fibers coupled with the H2-sensitive metal palladium, allows detection of dissolved hydrogen in liquid. By implementing these SPR sensors into AD, improvements to the biogas production process, even at small scales, may be achieved by guiding the process in the optimum direction, avoiding the collapse of the biological process. This review intends to assess the feasibility of online, cost-effective, rapid, and efficient detection of dissolved H2, as well as briefly assessing H2S, acetic acid, ammonia, and methane in AD by SPR.

13.
PLoS One ; 13(10): e0205447, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30300416

RESUMO

BACKGROUND: In diabetes research, the development of the artificial pancreas has been a major topic since continuous glucose monitoring became available in the early 2000's. A prerequisite for an artificial pancreas is fast and reliable glucose sensing. However, subcutaneous continuous glucose monitoring carries the disadvantage of slow dynamics. As an alternative, we explored continuous glucose sensing in the peritoneal space, and investigated potential spatial differences in glucose dynamics within the peritoneal cavity. As a secondary outcome, we compared the glucose dynamics in the peritoneal space to the subcutaneous tissue. MATERIAL AND METHODS: Eight-hour experiments were conducted on 12 anesthetised non-diabetic pigs. Four commercially available amperometric glucose sensors (FreeStyle Libre, Abbott Diabetes Care Ltd., Witney, UK) were inserted in four different locations of the peritoneal cavity and two sensors were inserted in the subcutaneous tissue. Meals were simulated by intravenous infusions of glucose, and frequent arterial blood and intraperitoneal fluid samples were collected for glucose reference. RESULTS: No significant differences were discovered in glucose dynamics between the four quadrants of the peritoneal cavity. The intraperitoneal sensors responded faster to the glucose excursions than the subcutaneous sensors, and the time delay was significantly smaller for the intraperitoneal sensors, but we did not find significant results when comparing the other dynamic parameters.


Assuntos
Técnicas Eletroquímicas , Glucose/análise , Tela Subcutânea , Administração Intravenosa , Animais , Técnicas Biossensoriais/métodos , Glicemia/análise , Eletrodos , Feminino , Glucose/administração & dosagem , Masculino , Modelos Animais , Cavidade Peritoneal , Suínos
14.
Sensors (Basel) ; 18(1)2018 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-29324648

RESUMO

We report on characterization of an optical fiber-based multi-parameter sensor concept combining localized surface plasmon resonance (LSPR) signal and interferometric sensing using a double-clad optical fiber. The sensor consists of a micro-Fabry-Perot in the form of a hemispherical stimuli-responsive hydrogel with immobilized gold nanorods on the facet of a cleaved double-clad optical fiber. The swelling degree of the hydrogel is measured interferometrically using the single-mode inner core, while the LSPR signal is measured using the multi-mode inner cladding. The quality of the interferometric signal is comparable to previous work on hydrogel micro-Fabry-Perot sensors despite having gold nanorods immobilized in the hydrogel. We characterize the effect of hydrogel swelling and variation of bulk solution refractive index on the LSPR peak wavelength. The results show that pH-induced hydrogel swelling causes only weak redshifts of the longitudinal LSPR mode, while increased bulk refractive index using glycerol and sucrose causes large blueshifts. The redshifts are likely due to reduced plasmon coupling of the side-by-side configuration as the interparticle distance increases with increasing swelling. The blueshifts with increasing bulk refractive index are likely due to alteration of the surface electronic structure of the gold nanorods donated by the anionic polymer network and glycerol or sucrose solutions. The recombination of biotin-streptavidin on gold nanorods in hydrogel showed a 7.6 nm redshift of the longitudinal LSPR. The LSPR response of biotin-streptavidin recombination is due to the change in local refractive index (RI), which is possible to discriminate from the LSPR response due to changes in bulk RI. In spite of the large LSPR shifts due to bulk refractive index, we show, using biotin-functionalized gold nanorods binding to streptavidin, that LSPR signal from gold nanorods embedded in the anionic hydrogel can be used for label-free biosensing. These results demonstrate the utility of immobilizing gold nanorods in a hydrogel on a double-clad optical fiber-end facet to obtain multi-parameter sensing.

15.
Sensors (Basel) ; 17(12)2017 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-29186839

RESUMO

We report on a new localized surface plasmon resonance (LSPR)-based optical fiber (OF) architecture with a potential in sensor applications. The LSPR-OF system is fabricated by immobilizing gold nanoparticles (GNPs) in a hydrogel droplet polymerized on the fiber end face. This design has several advantages over earlier designs. It dramatically increase the number nanoparticles (NP) available for sensing, it offers precise control over the NP density, and the NPs are positioned in a true 3D aqueous environment. The OF-hydrogel design is also compatible with low-cost manufacturing. The LSPR-OF platform can measure volumetric changes in a stimuli-responsive hydrogel or measure binding to receptors on the NP surface. It can also be used as a two-parameter sensor by utilizing both effects. We present results from proof-of-concept experiments exploring the properties of LSPR and interparticle distances of the GNP-hydrogel OF design by characterizing the distribution of distances between NPs in the hydrogel, the refractive index of the hydrogel and the LSPR attributes of peak position, amplitude and linewidth for hydrogel deswelling controlled with pH solutions.

16.
Anal Chem ; 81(9): 3630-6, 2009 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-19323502

RESUMO

Glucose-selective optical sensors were fabricated by incorporating 3-phenylboronic acid and a tertiary amine, dimethylaminopropylacrylamide, into a hydrogel matrix. Determination of glucose in solution is based on the glucose-induced contraction of the hydrogel. The gel was fabricated on the end of an optical fiber, and the optical length was measured by an interferometric technique. Previously it was found the gel could be tuned for enhanced glucose sensitivity and selectivity by varying the 3-phenylboronic acid/tertiary amine ratio. The properties of the responsive hydrogel as a glucose sensor were determined in more detail with respect to swelling kinetics and equilibrium swelling degree. Temperature effects, size variation, molecular interference, and reversibility were addressed. Results showed there was a good degree of reversibility, both for equilibrium swelling and swelling kinetics. Fabricated hydrogel sensors with slight differences in size yielded an overlapping relative response indicating an excellent degree of sensor reproducibility. The sensor proved to be temperature-dependent; by increasing the temperature from 25 to 37 degrees C, the swelling was about 4-fold more rapid, and a concomitant decrease in equilibrium swelling was seen. Identified interference from other analytes with determination of glucose was used a basis for selecting ethylenediaminetetraacetic acid (EDTA) as an anticoagulant for in vitro determination of glucose concentration in blood plasma. Glucose measurements performed in blood plasma were promising, showing that the sensor is capable of measuring physiological glucose levels in blood with a minimal effect from interfering molecules. The obtained results indicate that the developed sensor is a candidate for continuous monitoring of glucose in blood.


Assuntos
Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , Glicemia/análise , Hidrogéis/química , Monitorização Fisiológica/métodos , Fibras Ópticas , Glicemia/química , Humanos , Sensibilidade e Especificidade , Temperatura , Fatores de Tempo
17.
Anal Chem ; 80(13): 5086-93, 2008 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-18491924

RESUMO

A novel technique for detection of hydrogel swelling intended for use as a chemical or biological sensor, but also generally applicable for obtaining high-precision hydrogel swelling data, is described. The underlying design principle is that a hydrogel bound to the tip of an optical fiber constituting the environmental sensing element makes up a Fabry-Perot cavity for high-resolution detection of the optical length. The interference of light guided by the optical fiber and reflected at the two interfaces, fiber-gel and gel-solution, enables optical detection of the optical path length within the gel and degree of swelling of the gel. Acrylamide-based hydrogels with various molar fractions of the cationic monomer, N-(3-dimethylaminopropyl)acrylamide, were fabricated at the end of the fiber to demonstrate the feasibility of the approach. These sensors were investigated in solutions of varying ionic strength and pH. Relative gel length changes of the approximately 50-microm half-spherical gels were determined with a precision of approximately 2 nm. Moreover, the combination of good reproducibility and resolution of determination of swelling supports measurements of ionic strength changes in the millimolar range. Kinetic measurements for gel swelling induced by changes in ionic strengths had a time constant of approximately 2 s (half-spherical gel with 60-microm radius), whereas the time constants for gel swelling induced by changes in pH were observed in the range 90-130 s. Thus, different processes dictate the swelling rate in the two different cases. The results show that hydrogel equilibrium swelling and kinetics can be determined by the optical interference method with nanometer resolution, thus providing a unique platform for characterization of hydrogels swelling in general, and using functionalized hydrogels as biological sensors in particular.


Assuntos
Acrilamidas/química , Tecnologia de Fibra Óptica/métodos , Hidrogéis/química , Nanotecnologia/métodos , Tecnologia de Fibra Óptica/instrumentação , Concentração de Íons de Hidrogênio , Cinética , Modelos Químicos , Nanotecnologia/instrumentação , Fibras Ópticas , Concentração Osmolar , Pressão Osmótica , Soluções , Água/química
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