Evanescent light field trapping and transport of micro- and nanocrystals of biological macromolecules on a waveguide for serial crystallography.

A microfluidic evanescent field optical tweezer system was tested and developed for sample delivery of micro- and nanocrystals in serial crystallography. The fluid line was enforced, and the setup changed from vacuum pump-driven to syringe pump-driven. The pressure tolerance was found to be \SIrange{6}{10}{\bar} through repeated tests. Experiments with \SIrange{1}{2}{\um} polystyrene spheres and protein crystals showed that the system was able to trap micrometer-sized particles but that there were problems with sticking of especially protein crystals to the surface of the trapping region in the channel. Surface coating studies using cytop, \ac{PAH}, and \ac{BSA} were conducted. Cytop increased the cleanliness within the trapping region but did not change trapping behavior. \ac{PAH} decreased cleanliness in the trapping region and promoted sticking. \ac{BSA} adhered to the trapping region in a thin layer instead of the charged spheres tested and increased the ability of a charged sphere to move in the trap. However, the coatings did not provide a significant increase in trapping efficiency or the mobility of protein crystals (lysozyme, I3C, and thaumatin) tested. Decreasing the adhesion to the surface of the trap by modifying the crystallization protocol was also attempted but without success. The optical tweezers system tested in this thesis can not be directly applied in sample delivery in crystallography. Further studies and alterations are suggested, such as implementing a split waveguide with counter-propagating beams which can lift the particles some micrometers from the surface as demonstrated by Helle et al

Visualisation of Limb Movements by Accelerometers in Sedated Patients

The prognostication of neurological outcome in sedated ICU patients is challenging. Multiple clinical scoring schemes and examinations are used, where different motoric responses are important input variables. Accelerometery is a well-known technology widely applied in different fields of research and everyday electronic products. In medical research, accelerometers have been used in longitudinal epidemiological studies of physical activity and health as well as in ICU studies on the topic of activity, sleep and agitation monitoring. Similarly, accelerometric information could be a candidate to improve future neurological prognostication schemes. To the best of our knowledge, including a systematic review from 2015 [1], there are no published articles on automatic motion registration from ICU patients in connection to neurologic outcome prognosticatio

Investigation of the effect of clinically relevant interferents on glucose monitoring using near‐infrared spectroscopy

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 theywere 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 (APAP), 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

Surface-Enhanced Absorption Spectroscopy for Optical Fiber Sensing

Visible and near-infrared spectroscopy are widely used for sensing applications but suffer from poor signal-to-noise ratios for the detection of compounds with low concentrations. Enhancement by surface plasmon resonance is a popular technique that can be utilized to increase the signal of absorption spectroscopy due to the increased near-field created close to the plasmons. Despite interest in surface-enhanced infrared absorption spectroscopy (SEIRAS), the method is usually applied in lab setups rather than real-life sensing situations. This study aimed to achieve enhanced absorption from plasmons on a fiber-optic probe and thus move closer to applications of SEIRAS. A tapered coreless fiber coated with a 100 nm Au film supported signal enhancement at visible wavelengths. An increase in absorption was shown for two dyes spanning concentrations from 5 × 10−8 mol/L to 8 × 10−4 mol/L: Rhodamine 6G and Crystal Violet. In the presence of the Au film, the absorbance signal was 2–3 times higher than from an identically tapered uncoated fiber. The results confirm that the concept of SEIRAS can be implemented on an optical fiber probe, enabling enhanced signal detection in remote sensing applications

Feasibility of supercontinuum sources for use in glucose sensing by absorption spectroscopy

Diabetes mellitus 1 requires tight control of the blood glucose levels to avoid harmful effects of either too high (hyperglycemia) or too low (hypoglycemia) blood sugar. Due to the availability of low-cost components, fiber- coupled near infrared (NIR) absorption spectroscopy could be a feasible measurement method. From the molar absorptivity of glucose, it is shown that to achieve high accuracy using near infrared spectroscopy for glucose sensing, relative noise levels should not exceed 0:003 %. Two supercontinuum (SC) sources and one broadband lamp were investigated with a low-cost portable spectrometer. The SNR of the two SC sources was limited by amplitude fluctuations and could be improved by averaging. The SNR of the broadband source was found to be largely limited by the detector noise due to the weak intensity. 16 aqueous glucose samples ranging from 0 to 500mm were measured with the broadband source and an SC laser. A partial least squares regression (PLSR) model was built for both measurement sets, yielding root mean square errors of 49 and 54mm, illustrating how the limit of detection is restrained by the high relative intensity noise. A reference arm setup was built and could account for much of the variability of the SC source. A glucose measurement series using this setup and five samples (100 to 500mm) yielded a root mean square error of 10:6mm. The results indicate that an SC source can be feasible for absorption spectroscopy in a reference arm setup

Optimization of SERS Sensing With Micro-Lensed Optical Fibers and Au Nano-Film

We present the fabrication and characterization of optical fiber reflection probes based on surface-enhanced Raman scattering (SERS) and micro-lensed multimode fibers. For the SERS substrate, a nano-sphere lithography method is used. Comparison of SERS measurements with three different fiber probe configurations is presented. The proposed optimized structure shows a five times increase in SERS signal for dried Rhodamine 6G (R6G) and two times for aqueous R6G in comparison to a standard reflection configuration. Measurements of different concentrations of R6G in a water solution with an limit of detection (LOD) equal to 10 -7 M are demonstrated

Glucose sensing by absorption spectroscopy using lensed optical fibers

The bulkiness of common transmission spectroscopy probes prevents applicability at remote locations such as within the body. We present the fabrication and characterization of lensed fibers for transmission spectroscopy in the near infrared. Eigenmode simulations and measurements of the coupling efficiency are presented and applied to design the setup corresponding to the sample absorption. Sensing capabilities are demonstrated on aqueous glucose samples ranged 80 to 500 mM obtaining a mean absolute percentage error of calibration of 4.3%. With increased flexibility, transmission spectroscopic sensors at remote locations may be achievable, for example applied to in vivo continuous glucose monitoring

Towards Fiber-Optic Raman Spectroscopy for Glucose Sensing

We demonstrate a multimode optical fiber sensor for spectroscopic Raman measurements of glucose concentration for the application in intraperitoneal glucose detection in diabetic patients. A regression model with a RMSEC of 2.2 mM was obtained

A Review of Optical Methods for Continuous Glucose Monitoring

Frequent glucose monitoring is a fundamental part of diabetes management, and good glucose control is important for long-term health outcomes. New types of electrochemical sensors that allow for continuous glucose monitoring (CGM) have become an important tool for diabetes management, although they still have drawbacks such as short lifetime and a need for frequent calibration. Other technologies are still being researched for CGM, in an attempt to replace the electrochemical sensors. Optical methods have several advantages for CGM, including potentially long sensor lifetimes and short measurement times, and many developments have been made over the last decades. This paper will review optical measurement methods for CGM, their challenges, and the current research status. The different methods will be compared, and the future prospects for optical methods will be discussed

A miniaturized ball-lensed fiber optic NIR transmission spectroscopy-based glucose sensor

A novel ball-lensed fiber transmission sensor is presented aimed at in vivo continuous glucose monitoring of diabetics. Preliminary results yield 20 mM RMSE, limited by mechanical instability. The design enables flexibility and further miniaturization