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Engholm, Magnus
Publications (10 of 39) Show all publications
Engholm, M., Hammarling, K., Andersson, H., Sandberg, M. & Nilsson, H.-E. (2019). A Bio-Compatible Fiber Optic pH Sensor Based on a Thin Core Interferometric Technique. Photonics, 6(1), Article ID 11.
Open this publication in new window or tab >>A Bio-Compatible Fiber Optic pH Sensor Based on a Thin Core Interferometric Technique
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2019 (English)In: Photonics, ISSN 2304-6732, Vol. 6, no 1, article id 11Article in journal (Refereed) Published
Abstract [en]

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 pHsensors concepts have been proposed, however, there is still a need for improved sensor solutionswith respect to reliability, durability and miniaturization but also for multiparameter sensing. Here wepresent a conceptual verification, which includes theoretical simulations as well as experimentalevaluation of a fiber optic pH-sensor based on a bio-compatible pH sensitive material not previouslyused 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 splicedbetween two standard single mode fibers. The working principle of the sensor is simulated by usingCOMSOL Multiphysics. The simulations are used as a guideline for the construction of the sensorsthat 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 developedsensor concept can find future use in many medical- or bio-chemical applications as well as inenvironmental monitoring of large areas. Challenges encountered during the sensor developmentdue to variation in the design parameters are discussed.

Keywords
interferometric, Mach-Zehnder, pH, sensor, hydrogel, simulation
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-35646 (URN)10.3390/photonics6010011 (DOI)000464341200003 ()2-s2.0-85063143389 (Scopus ID)
Note

MDPI Photonics Special Issue "Advanced Optical Materials and Devices"

Available from: 2019-02-14 Created: 2019-02-14 Last updated: 2019-05-22Bibliographically approved
Balliu, E., Engholm, M. & Nilsson, H.-E. (2019). A compact, single-frequency, high-power, SBS-free, Yb-doped single-stage fiber amplifier. In: W. Andrew Clarkson and Ramesh K. Shori (Ed.), Proceedings of SPIE - The International Society for Optical Engineering: . Paper presented at Solid State Lasers XXVIII: Technology and Devices 2019, San Francisco, California, United States, 5-7 February, 2019 (pp. 6pp). SPIE - International Society for Optical Engineering, 10896, Article ID 1089618.
Open this publication in new window or tab >>A compact, single-frequency, high-power, SBS-free, Yb-doped single-stage fiber amplifier
2019 (English)In: Proceedings of SPIE - The International Society for Optical Engineering / [ed] W. Andrew Clarkson and Ramesh K. Shori, SPIE - International Society for Optical Engineering, 2019, Vol. 10896, p. 6pp-, article id 1089618Conference paper, Published paper (Refereed)
Abstract [en]

Interest in compact, single-frequency fiber amplifier has increased within many scientific and industrial applications. The main challenge is the onset of nonlinear effects, which limit their power scaling. Here we demonstrate a compact, high-power, single-frequency, polarization-maintaining, continous-wave fiber amplifier using only one amplification stage. We developed the fiber amplifier using a master oscillator fiber amplifier architecture, where a low-noise, single-frequency, solid-state laser operating at 1064 nm was used as a seed source. We evaluated the amplifier's performance by using several state-of-the-art, small-core, Ytterbium (yb)-doped fibers, as well as an in-house-made, highly Yb-doped fiber. An output power of 82 W was achieved with no sign of stimulated Brillouin scattering. A good beam quality and a polarization extinction ratio (PER) of > 25 dB were achieved. The compact fiber amplifier can be a competitive alternative to multi stage designed fiber amplifiers.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2019
Keywords
Single-frequency laser, Ytterbium-doped fiber amplifier, stimulated Brillouin scattering, high-power fiber amplifier, compact fiber amplifier
National Category
Other Physics Topics
Identifiers
urn:nbn:se:miun:diva-36042 (URN)10.1117/12.2511049 (DOI)2-s2.0-85068317380 (Scopus ID)
Conference
Solid State Lasers XXVIII: Technology and Devices 2019, San Francisco, California, United States, 5-7 February, 2019
Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-08-12Bibliographically approved
Andersson, H., Šuly, P., Thungström, G., Engholm, M., Zhang, R., Mašlík, J. & Olin, H. (2019). PEDOT: PSS thermoelectric generators printed on paper substrates. Journal of Low Power Electronics and Applications, 9(2)
Open this publication in new window or tab >>PEDOT: PSS thermoelectric generators printed on paper substrates
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2019 (English)In: Journal of Low Power Electronics and Applications, ISSN 2079-9268, Vol. 9, no 2Article in journal (Refereed) Published
Abstract [en]

Flexible electronics is a field gathering a growing interest among researchers and companies with widely varying applications, such as organic light emitting diodes, transistors as well as many different sensors. If the circuit should be portable or off-grid, the power sources available are batteries, supercapacitors or some type of power generator. Thermoelectric generators produce electrical energy by the diffusion of charge carriers in response to heat flux caused by a temperature gradient between junctions of dissimilar materials. As wearables, flexible electronics and intelligent packaging applications increase, there is a need for low-cost, recyclable and printable power sources. For such applications, printed thermoelectric generators (TEGs) are an interesting power source, which can also be combined with printable energy storage, such as supercapacitors. Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), or PEDOT:PSS, is a conductive polymer that has gathered interest as a thermoelectric material. Plastic substrates are commonly used for printed electronics, but an interesting and emerging alternative is to use paper. In this article, a printed thermoelectric generator consisting of PEDOT:PSS and silver inks was printed on two common types of paper substrates, which could be used to power electronic circuits on paper. 

Keywords
Paper substrates, PEDOT:PSS, Seebeck coefficient, Stencil print, Thermoelectric generator
Identifiers
urn:nbn:se:miun:diva-36667 (URN)10.3390/jlpea9020014 (DOI)2-s2.0-85065493304 (Scopus ID)
Available from: 2019-07-09 Created: 2019-07-09 Last updated: 2019-07-09Bibliographically approved
Zhang, R., Hummelgård, M., Örtegren, J., Yang, Y., Andersson, H., Balliu, E., . . . Olin, H. (2019). Sensing body motions based on charges generated on the body. Nano Energy, 63, Article ID 103842.
Open this publication in new window or tab >>Sensing body motions based on charges generated on the body
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2019 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 63, article id 103842Article in journal (Refereed) Published
Abstract [en]

The sensing of body motions is of great importance in areas such as healthcare, rehabilitation, and human-computer interactions. Different methods have been developed based on visual or electrical signals. However, such signals are acquired by external devices and are not intrinsic signals that are created on the body. Here, we report a new universal body motion sensor (UBS) to detect motions based on the intrinsic contact electrification (CE) of the skin or electrical induction (EI) of the body. The CE or EI generates charges on the body, leading to potential differences between the body and ground that can be measured to identify different body motions, such as motions of the head, arms, fingers, waist, legs, feet and toes. Proof-of-concept experiments have demonstrated that the UBS can be used to monitor the conditions of people with Parkinson's disease (PD) and to quantitatively monitor the recovery of those with a leg injury, suggesting great potential for healthcare applications.

Keywords
Body motions, Sensors, Charges, Contact electrification, Electrical induction, Healthcare
Identifiers
urn:nbn:se:miun:diva-36826 (URN)10.1016/j.nanoen.2019.06.038 (DOI)000480422400034 ()
Available from: 2019-08-12 Created: 2019-08-12 Last updated: 2019-09-02Bibliographically approved
Hammarling, K., Engholm, M., Andersson, H., Sandberg, M. & Nilsson, H.-E. (2018). Broad-Range Hydrogel-Based pH Sensor with Capacitive Readout Manufactured on a Flexible Substrate. Chemosensors, 6(3), Article ID 30.
Open this publication in new window or tab >>Broad-Range Hydrogel-Based pH Sensor with Capacitive Readout Manufactured on a Flexible Substrate
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2018 (English)In: Chemosensors, ISSN 2227-9040, Vol. 6, no 3, p. 15article id 30Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Basel, Switzerland: MDPI, 2018. p. 15
Keywords
interdigital, hydrogel, penetration depth, pH, sensor, coating, thin film, laser ablation, oligo (β-amino esters)
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-34203 (URN)10.3390/chemosensors6030030 (DOI)000448395400006 ()2-s2.0-85052627188 (Scopus ID)
Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2019-05-09Bibliographically approved
Muri, H. I., Hammarling, K., Wahl, M., Engholm, M. & Hjelme, D. R. (2018). Combining interferometric sensors for dual parameter fiber optic chemical sensing. In: Optics InfoBase Conference Papers: . Paper presented at 26th International Conference on Optical Fiber Sensors, OFS 2018, Lausanne, Switzerland, 24 September 2018 through 28 September 2018. OSA - The Optical Society, Article ID WF80.
Open this publication in new window or tab >>Combining interferometric sensors for dual parameter fiber optic chemical sensing
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2018 (English)In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2018, article id WF80Conference paper, Published paper (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
OSA - The Optical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:miun:diva-35437 (URN)10.1364/OFS.2018.WF80 (DOI)2-s2.0-85059485004 (Scopus ID)9781557528209 (ISBN)
Conference
26th International Conference on Optical Fiber Sensors, OFS 2018, Lausanne, Switzerland, 24 September 2018 through 28 September 2018
Available from: 2019-01-14 Created: 2019-01-14 Last updated: 2019-01-14Bibliographically approved
Zhang, R., Engholm, M., Hummelgård, M., Andersson, H., Örtegren, J. & Olin, H. (2018). High-performance transparent and flexible electrodes made by flash-light sintering of gold nanoparticles. ACS Applied Energy Materials, 1(12), 7191-7198
Open this publication in new window or tab >>High-performance transparent and flexible electrodes made by flash-light sintering of gold nanoparticles
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2018 (English)In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 1, no 12, p. 7191-7198Article in journal (Refereed) Published
Abstract [en]

Metallic nanowire-based transparent electrodes (TEs) are potential alternatives to indium tin oxide (ITO). To achieve a high performance [sheet resistance (Rs) < 100 Ω/sq, transmittance (T%) > 90%], the nanowires must have a high length-to-diameter (L/D) ratio to minimize the number of wire-to-wire junctions. Attempts to produce TEs with gold nanowires have been made, and the results reveal difficulties in achieving the requirements. A successful strategy involves creating templated gold nanonetworks through multiple procedures. Here, we present a simple and efficient method that uses flash-light sintering of a gold nanonetwork film into gold TEs (Rs: 82.9 Ω/sq, T %: 91.79%) on a thin polycarbonate film (25 μm). The produced gold TEs have excellent mechanical, electrical, optical, and chemical stabilities. Mechanisms of the formation of gold nanonetworks and the effect of flash-light have been analyzed. Our findings provide a scalable process for producing transparent and flexible gold electrodes with a total processing time of less than 8 min without the use of heating, vacuum processing, and organic chemicals and without any material loss. This is possible because all the gold nanoparticles have been aggregated and filtrated on the filter membranes. The area density of gold is 0.094 g/m2 leading low material costs, which is very competitive with the price of commercial TEs.

Keywords
transparent electrode, flexible electrode, gold nanoparticles, flash-light sintering, high performance
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:miun:diva-35380 (URN)10.1021/acsaem.8b01649 (DOI)000458706800063 ()2-s2.0-85064752503 (Scopus ID)
Available from: 2019-01-03 Created: 2019-01-03 Last updated: 2019-07-08Bibliographically approved
Maslik, J., Andersson, H., Forsberg, V., Engholm, M., Zhang, R. & Olin, H. (2018). PEDOT:PSS temperature sensor ink-jet printed on paper substrate. Journal of Instrumentation, 13, Article ID C12010.
Open this publication in new window or tab >>PEDOT:PSS temperature sensor ink-jet printed on paper substrate
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2018 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 13, article id C12010Article, review/survey (Refereed) Published
Abstract [en]

In this work we present an ink-jet printed temperature sensor consisting of PEDOT:PSSprinted on paper suitable for packaging, flexible electronics and other printed applications. Thesubstrate showed to have a large influence on both the resistance aswell as the temperature sensitivityof the PEDOT:PSS ink. This effect is most likely due to NaCl content in the photo paper coating,which reacts with the PEDOT:PSS. The temperature coefficient of a prepared device of  α= -0.030 relative to room temperature (22°C) was measured, which is higher than compared to for exampleSilicon α = -0.075.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2018
Keywords
Detector design and construction technologies and materials; Manufacturing
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-35891 (URN)10.1088/1748-0221/13/12/C12010 (DOI)000452801600005 ()
Projects
LEAP
Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-04-05Bibliographically approved
Zhang, R., Hummelgård, M., Forsberg, V., Andersson, H., Engholm, M., Öhlund, T., . . . Olin, H. (2018). Photoconductivity of acid exfoliated and flash-light-processed MoS2 films. Scientific Reports, 8, Article ID 3296.
Open this publication in new window or tab >>Photoconductivity of acid exfoliated and flash-light-processed MoS2 films
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 3296Article in journal (Refereed) Published
Abstract [en]

MoS2 has been studied intensively during recent years as a semiconducting material in several fields, including optoelectronics, for applications such as solar cells and phototransistors. The photoresponse mechanisms of MoS2 have been discussed but are not fully understood, especially the phenomenon in which the photocurrent slowly increases. Here, we report on a study of the photoresponse flash-light-processed MoS2 films of different thicknesses and areas. The photoresponse of such films under different light intensities and bias voltages was measured, showing significant current changes with a quick response followed by a slow one upon exposure to pulsed light. Our in-depth study suggested that the slow response was due to the photothermal effect that heats the MoS2; this hypothesis was supported by the resistivity change at different temperatures. The results obtained from MoS2 films with various thicknesses indicated that the minority-carrier diffusion length was 1.36 mu m. This study explained the mechanism of the slow response of the MoS2 film and determined the effective thickness of MoS2 for a photoresponse to occur. The method used here for fabricating MoS2 films could be used for fabricating optoelectronic devices due to its simplicity.

National Category
Physical Sciences
Identifiers
urn:nbn:se:miun:diva-33302 (URN)10.1038/s41598-018-21688-0 (DOI)000425380900079 ()29459668 (PubMedID)2-s2.0-85061713034 (Scopus ID)
Available from: 2018-03-19 Created: 2018-03-19 Last updated: 2019-03-20Bibliographically approved
Forsberg, V., Andersson, H., Engholm, M., Thungström, G., Zhang, R., Hummelgård, M., . . . Norgren, M. (2018). Photodetector of multilayer exfoliated MoS2 deposited on polyimide films. In: : . Paper presented at 20th International Workshop on Radiation Imaging Detectors, Sundsvall, 24-28 June, 2018.
Open this publication in new window or tab >>Photodetector of multilayer exfoliated MoS2 deposited on polyimide films
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2018 (English)Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

We fabricated a photodetector based on multilayer molybdenum disulfide (MoS2) by micromechanical cleavage of a molybdenite crystal using a polyimide film. We deposited 40 nm of gold by vacuum sputtering and copper tape was used for the contacts.  Without any surface treatment, we achieved high responsivity at different incident optical power. The calculated responsivity was 23 mA/W of incident optical power in the range between 400 and 800 nm. For the responsivity measurement it was estimated that MoS2 have a bandgap of 1.6 eV, which lies between monolayer and multilayer films. The thickness of the MoS2 thin film was determined by Raman spectroscopy evaluating the difference between the in plane  and out of plane  Raman modes. The measurement of IV curves indicated Ohmic contacts in respect to the Au regardless of the incident optical power. Our device fabrication was much simpler than previous reported devices and can be used to test the light absorption and luminescence capabilities of exfoliated MoS2.

Keywords
Photodetector, MoS2
National Category
Chemical Engineering Materials Engineering Physical Sciences
Identifiers
urn:nbn:se:miun:diva-34035 (URN)
Conference
20th International Workshop on Radiation Imaging Detectors, Sundsvall, 24-28 June, 2018
Funder
Knowledge Foundation, 2600364
Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-08-16Bibliographically approved
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