| 1. |
- Engholm, Magnus, et al.
(författare)
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A bio-compatible fiber optic pH sensor based on a thin core interferometric technique
- 2019
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Ingår i: Photonics. - : MDPI AG. - 2304-6732. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing demand for compact, reliable and versatile sensor concepts for pH-level monitoring within several industrial, chemical as well as bio-medical applications. Many pH sensors concepts have been proposed, however, there is still a need for improved sensor solutions with respect to reliability, durability and miniaturization but also for multiparameter sensing. Here we present a conceptual verification, which includes theoretical simulations as well as experimental evaluation of a fiber optic pH-sensor based on a bio-compatible pH sensitive material not previously used in this context. The fiber optic sensor is based on a Mach-Zehnder interferometric technique, where the pH sensitive material is coated on a short, typically 20-25 mm thin core fiber spliced between two standard single mode fibers. The working principle of the sensor is simulated by using COMSOL Multiphysics. The simulations are used as a guideline for the construction of the sensors that have been experimentally evaluated in different liquids with pH ranging from 1.95 to 11.89. The results are promising, showing the potential for the development of bio-compatible fiber optic pH sensor with short response time, high sensitivity and broad measurement range. The developed sensor concept can find future use in many medical- or bio-chemical applications as well as in environmental monitoring of large areas. Challenges encountered during the sensor development due to variation in the design parameters are discussed. © 2019 by the authors.
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| 2. |
- Hammarling, Krister, 1968-, et al.
(författare)
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A combined glucose and pH sensor on a single optical fiber for continuous point-of-care testing
- 2018
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Ingår i: SPIE BIOS, Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XVIII. - : SPIE - International Society for Optical Engineering.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Stress-induced hyperglycemia is very common for patients in intensive care units, which can become fatal if left uncontrolled. Blood glucose concentrations for patients at the intensive care units should therefore be monitored at all times. To be successful in monitoring the glucose concentrations of patients, the sensor needs to be fast, accurate and able to measure in real time. In addition, the pH level should be monitored, as a diagnostic parameter by itself, or to improve the reliability of the glucose measurement. To address this challenge, a fiber optic sensor for dual parameter measurement of glucose concentration and pH level for use in point-of-care testing has been developed. The sensor utilizes two stimuli responsive hydrogels to create two interferometers combined on one single mode fiber. The sensor is created by splicing a short section of thin-core fiber (SM450) coated with a pH-sensitive polymer, which constitutes a Mach-Zehnder type interferometer. The glucose is measured with a low finesse Fabry-Perot cavity made by polymerizing a glucose sensitive hydrogel hemisphere at the end face of the fiber. A versatile Fourier transform based, low pass filter was developed, which enable evaluation of the two signals independently. Our results show the feasibility of measuring glucose concentration and pH level by using a single fiber. This dual parameter and single point fiber optic biosensor is expected to be of great interest for in vivo measurements in medical applications where pH and glucose, as specific markers are monitored in real time, during or after surgery.
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| 3. |
- Hammarling, Krister, 1968-, et al.
(författare)
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Blood pH optrode based on evanescent waves and refractive index change
- 2014
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 9780819498519 ; , s. Art. no. 89381F-
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Konferensbidrag (refereegranskat)abstract
- Sensing pH in blood with an silica multimode optical fiber. This sensor is based on evanescent wave absorption and measures the change of the refractive index and absorption in a cladding made of a biocompatible Polymer. In contrast to many existing fiber optical sensors which are based upon different dyes or florescent material to sense the pH, here presents a solution where a part of the cladding is replaced with a Poly (β-amino ester) made of 1.4-Butanediol diacrylate, Piperazine, and Trimethylolpropane Triacrylate. Piperazine has the feature of changing its volume by swelling or shrinking in response to the pH level. This paper utilizes this dimension effect and measure the refractive index and the absorption of the cladding in respect to different pH-levels. The alteration of refractive index also causes a change in the absorption and therefore the output power changes as a function of the pH level. The sensor is sensitive to pH in a wide spectral range and light absorbency can be observed for wavelengths ranging from UV to far IR. © 2014 SPIE.
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| 4. |
- Hammarling, Krister, 1968-, et al.
(författare)
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Broad-range hydrogel-based pH sensor with capacitive readout manufactured on a flexible substrate
- 2018
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Ingår i: Chemosensors. - Basel, Switzerland : MDPI AG. - 2227-9040. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- Environmental monitoring of land, water and air, is an area receiving greater attention because of human health and safety concerns. Monitoring the type of pollution and concentration levels is vital, so that appropriate contingency plans can be determined. To effectively monitor the environment, there is a need for new sensors and sensor systems that suits these type of measurements. However, the diversity of sensors suitable for low, battery powered- and large area sensor systems are limited. We have manufactured and characterized a flexible pH sensor using laser processing and blade coating techniques that is able to measure pH between 2.94 and 11.80. The sensor consists of an interdigital capacitance with a pH sensitive hydrogel coating. Thin sensors can reach 95% of their final value value within 3 min, and are stable after 4 min. Good repeatability was achieved in regard to cycling of the sensor with different pH and multiple measurements from dry state. We have also studied the relation between an interdigital capacitance penetration depth and hydrogels expansion. We believe that our passive sensor is suitable to be used in low power and large area sensor networks.
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| 5. |
- Hammarling, Krister, 1968-, et al.
(författare)
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Dual parameter fiber optic sensor combining a Fabry-Perot and a Mach-Zehnder interferometer
- 2017
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Ingår i: Proceedings of IEEE Sensors. - : IEEE. - 9781509010127 ; , s. 1440-1442
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A new concept for dual parameter fiber optic sensorhas been developed and characterized, both in a two-fiber andsingle-fiber configuration. The liquid sensor measures ethanolconcentration with a stimuli responsive hydrogel whichconstitutes a low finesse Fabry-Perot cavity, and refractive indexwith a Mach-Zehnder type fiber optic interferometer. The two-fiber configuration utilize a fiber optic 1310/1550 nm wavelengthdivision multiplexer to separate the two parameters, while aversatile filtering algorithm extracts and separates the twoparameters in the single-fiber configuration. No cross talk wereobserved for the measured parameters of free spectral range andrefractive index for the two-fiber configurations, while for thesingle fiber configuration cross-talk were observed. The twoconfigurations prove to be versatile dual parametric fiber opticsensor concepts for accurate detection of specific parameters,based on stimuli responsive hydrogels.
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| 6. |
- Hammarling, Krister, 1968-, et al.
(författare)
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FBG based upon evaporated Silica nano particles
- 2011
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Ingår i: 1st EOS Topical Meetingon On Micro- and Nano-Optoelectronic Systems, Bremen, December 7-9, 2011.
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Konferensbidrag (refereegranskat)abstract
- A fiber bragg grating was made by evaporating silica nano particles on the outside of a multimode silica fiber core using EISA method. We demonstrate that a cost effective bragg filter may be built by evaporating nano particles directly on a fiber core, which is tunable with the particle size.
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| 7. |
- Hammarling, Krister, 1968-, et al.
(författare)
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Fiber Bragg Grating filter using Evaporated Induced Self Assembly of silica nano particles
- 2014
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. ; , s. Art. no. 898225-
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Konferensbidrag (refereegranskat)abstract
- In the present work we conduct a study of ber lters produced by evaporation of silica particles upon aMM-ber core. A band lter was designed and theoretically veried using a 2D Comsol simulation model ofa 3D problem, and calculated in the frequency domain in respect to refractive index. The ber lters werefabricated by stripping and chemically etching the middle part of an MM-ber until the core was exposed. Amono layer of silica nano particles were evaporated on the core using an Evaporation Induced Self-Assembly(EISA) method. The experimental results indicated a broader bandwidth than indicated by the simulationswhich can be explained by the mismatch in the particle size distributions, uneven particle packing and nallyby eects from multiple mode angles. Thus, there are several closely connected Bragg wavelengths that buildup the broader bandwidth. The experimental part shows that it is possible by narrowing the particle sizedistributing and better control of the particle packing, the lter eectiveness can be greatly improved.
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| 8. |
- Hammarling, Krister, 1968-
(författare)
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Hydrogel-based pH-sensors : Development and characterisation of optical and electrical pH sensors based on stimuli-responsive hydrogels
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ability to measure the chemical parameter pH is of high importance in many areas. With new government regulations and evolving markets, there is a strong motivation for improving such measurements and conducting research on new types of pH sensors and sensor materials. Stimuli-responsive hydrogels (a group of polymers) have attracted a lot of attention in recent decades, due to their ability to be customized to suit many applications. One specific area where they have attracted attention is pH sensor technology.Two stimuli-responsive hydrogels are used in this thesis. One is a non-toxic hydrogel, 1,4-acryl-terminated oligo(beta-amino esters) (1,4-AOBAE). Although it was previously used in drug- and DNA- delivery systems, it has not (to my knowledge) been used in a sensor configuration, and thus it is interesting to study. The second hydrogel, 1,3-acryl-terminated oligo(beta-amino esters) (1,3-AOBAE), is an improved variant of the first one. This improved hydrogel was synthesized because the original hydrogel crystallizes at room temperature, which meant that it was not optimal for various coating techniques. This hydrogel was characterized and verified for pH responsivity in two sensor configurations: electrical and optical. Designing a hydrogel for a specific application can be a complex procedure due to the many synthesizing parameters. For example, increasing a hydrogel's mechanical strength by introducing a higher degree of cross linking, leads to a smaller mesh size, which in turn leads to a lower diffusion rate and less solution absorption. The two hydrogels examined in this thesis respond to pH changes by absorbing or desorbing water; this change in the hydrogel's water content also changes its effective refractive index and permittivity. These changes can be measured using optical or electrical sensor systems. Three types of sensor systems were used in this thesis to verify the hydrogel's pH response and to ensure that they are suitable for use in thin-film techniques on various substrates (e.g. glass and plastic). The experimental results prove that these hydrogels are suitable for use in both electrical and optical sensor configurations. For electrical systems, a pH range of approximately 3-12 was achieved, and for optical, the range was approximately 2-12. These ranges can likely be improved, as the sensor film delaminated from the substrate at low pHs due to adhesion problems and as measurements above 12 were not conducted.The findings of this thesis could, after more research, have strong implications for the development of improved pH-sensor configurations, especially for medical and healthcare applications and in environmental monitoring.
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| 9. |
- Hammarling, Krister, 1968-, et al.
(författare)
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Synthesis, Curing Behavior and Swell Tests of pH-Responsive Coatings from Acryl-Terminated Oligo(beta-Amino Esters)
- 2018
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Ingår i: CHEMOSENSORS. - : MDPI AG. - 2227-9040. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- The ability of acryl-terminated oligo(beta-amino esters) (AOBAE) to be coated on fibers and printed electronics without solvents and to be cross-linked to a pH-responsive coatings, makes AOBAE-based coatings a potential type of pH-sensor coating. However, there are currently no reports of AOBAEs used as a pH-responsive coating material in sensor applications. Here we present an investigation of the synthesis, curing behavior and swell tests of AOBAEs. AOBAEs were synthesized from reacting an excess of asymmetric diacrylates with piperazine without the use of any solvents. They were then cross-linked to an insoluble network by UV-curing. Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the AOBAEs. NMR was used to clarify the irregular structure of the AOBAE. FTIR was used to monitor the effects of UV-curing dose and air exposure on monomer conversion during curing. An interferometric technique was used to monitor the swelling behavior of the coating in response to pH variations. Swell experiments showed that the AOBAE also responded to pH variations after polymerization. Therefore, AOBAE is an interesting class of material with potential use as a pH responsive coating in optical-and printed electronics pH-sensors applications.
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| 10. |
- Muri, H. I., et al.
(författare)
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Combining interferometric sensors for dual parameter fiber optic chemical sensing
- 2018
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- Long and short path length differences interferometric sensing modalities have been combined based on immobilizing hydrogel on thin-core optical fiber end face. Dual parameter sensing of hydrogel swelling and refractive index was demonstrated.
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