TY - CHAP A1 - Kefer, Stefan A1 - Rosenberger, Manuel A1 - Hessler, Steffen A1 - Girschikofsky, Maiko A1 - Belle, Stefan A1 - Roth, Gian-Luca A1 - Schmauß, Bernhard A1 - Hellmann, Ralf T1 - Fabrication and Applications of Polymer Planar Bragg Grating Sensors based on Cyclic Olefin Copolymers T2 - 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) N2 - This contribution reviews recent advancements, current research and possible applications of polymer planar Bragg grating (PPBG) sensors with a focus on the utilization of cyclic olefin copolymer (COC) substrates. COC-PPBGs can be handled and fabricated efficiently by employing a single writing step procedure which features simultaneous generation of waveguide and Bragg grating structure within an injection molded substrate. The resulting photonic structures exhibit an attenuation as low as 1.2 dB cm-1 and a reflectivity up to 99 %. The potential of COC-PPBGs for high-temperature applications is proven by demonstrating temperature measurements up to 160 °C. Moreover, it is possible to employ single PPBGs for multidimensional stress and strain sensing or even three-dimensional shape reconstruction. Due to their excellent properties, it is feasible to integrate COC-PPBGs into commercial-grade carbon fiber reinforced polymer workpieces for structural health monitoring. Furthermore, utilization of appropriate coatings enables functionalization of PPBGs for refractive index sensing and thus biochemical applications. Beside the fabrication and characterization of COC-based PPBGs, this contribution exemplifies and reviews such applications. KW - Bragg gratings , Gratings , Optical waveguides , Temperature sensors , Substrates KW - Optischer Sensor KW - Bragg-Reflektor Y1 - 2020 UR - https://ieeexplore.ieee.org/document/9021801 SN - 978-1-7281-5304-9 U6 - https://doi.org/10.1109/PIERS-Fall48861.2019.9021801 SP - 647 EP - 655 PB - Institute of Electrical and Electronics Engineers ER - TY - JOUR A1 - Körbitzer, Berit Silke A1 - Krauß, Peter A1 - Belle, Stefan A1 - Schneider, Jörg A1 - Thielemann, Christiane T1 - Electrochemical Characterization of Graphene Microelectrodes for Biological Applications JF - ChemNanoMat N2 - Graphene is a promising material both as a coating for existing neural electrodes as well as for transparent electrodes made exclusively from graphene. We studied graphene‐based microelectrodes by investigating their recording and stimulation properties in order to evaluate their suitability for neuronal implants. In this work, we compare three different electrode material compositions. Microelectrode arrays (MEA) with an electrode size of about 700 μm2 were prepared of gold, graphene on gold, and plain graphene on glass substrate. In order to reduce polymer contamination during graphene transfer, we employed a polymer‐free transfer and lift‐off process. Impedance studies revealed a value of 2.3 MΩ at 1 kHz for plain, and 0.88 MΩ for graphene on gold. Neuronal recording experiments showed a sufficient SNR for both graphene‐based materials and a stable impedance, unaffected by surface degradation metal electrodes are known for. Stimulation measurements yielded a charge injection capacity of 0.15 mC/cm2 using biphasic pulses of 1 ms and 1 μA transparent graphene electrodes. Cyclic voltammetry revealed a large voltage range of −1.4 V to +1.6 V before water electrolysis occurs. Graphene‐coated gold microelectrodes show enhanced recording properties, whereas plain graphene electrodes might be better suited for stimulation applications. KW - Graphene KW - Microelectrodes KW - Stimulation KW - Neural Recording KW - Neural Interface KW - Mikroelektrode KW - Array Y1 - 2019 U6 - https://doi.org/10.1002/cnma.201800652 VL - 2019 IS - 5:4 SP - 427 EP - 435 ER - TY - CHAP A1 - Nick, Christoph A1 - Hock, Christina A1 - Emmerich, Florian A1 - Belle, Stefan A1 - Thielemann, Christiane A1 - Asmus, Tim A1 - Loose, Thomas A1 - Wienand, Karlheinz T1 - Ultrathin gold as sensor platform for biomolecules T2 - 2015 International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO), Changchun, China N2 - Due to the increasing number of diabetes patients worldwide there is an enormous need for accurate, fast and someday also continuous or even closed loop monitoring of blood glucose level. More than 50 years after Clark and Lyons proposed the first glucose enzyme electrodes this concept is still widely in use today. Most concepts use the enzyme glucose oxidase (GOx) that reacts with glucose. These reactions cause a current that is proportional to the amount of glucose present at the sensor. Thus, if the sample volume is known, the blood sugar level can be measured. Although these electrodes have been in use for so long they have the disadvantage of a limited shelf time. In this work we present an enzyme free approach for glucose detection applying ultrathin gold films. According to the basic Fuchs-Sondheimer-theory and other more sophisticated models the resistivity of ultrathin metal films is dominated by scattering effects at their surface. Chemical reactions at the metallic surface are expected to change the conductivity properties and thus these changes can be used to detect molecules. This can be done by creating a self-assembled monolayer at the gold surface. When molecules such as glucose bind to the end groups of this layer the electron scattering and thus the conductivity of the film is expected to change. Ultrathin gold films with a thickness of 6 nm show the largest relative change in resistivity and are thus the preferred film thickness for this application. These gold films show a significant change in resistance when model molecules sodium sulfide and dextran are present, whereas the resistance of a platinum reference electrode does not change significantly. KW - ultrathin gold KW - biosensor KW - glucose KW - enzyme free glucose sensor KW - Biosensor KW - Dünne Schicht KW - Gold Y1 - 2015 U6 - https://doi.org/10.1109/3M-NANO.2015.7425462 ER - TY - JOUR A1 - Flachs, Dennis A1 - Etzel, Johannes A1 - Mayer, Margot A1 - Harbecke, Frederic A1 - Belle, Stefan A1 - Rickmeyer, Tim A1 - Thielemann, Christiane T1 - Characterization of electrically conductive, printable ink based on alginate hydrogel and graphene nanoplatelets JF - Biomedical Engineering Advances N2 - In recent years, there has been an increasing interest in electrically conductive hydrogels for a wide range of biomedical applications, like tissue engineering or biosensors. In this study, we present a cost-effective conductive hydrogel based on alginate and graphene nanoplatelets for extrusion-based bioprinters. The hydrogel is prepared under ambient conditions avoiding high temperatures detrimental for cell culture environments. Investigation of the hydrogel revealed a conductivity of up to 7.5 S/cm, depending on the ratio of platelets. Furthermore, in vitro tests with human embyronic kidney cells - as an example cell type - showed good adhesion of the cells to the surface of the conductive hydrogel. Electrochemical measurements revealed a low electrode impedance which is desirable for the extracellular recording, but also low electrode capacitance, which is unfavorable for electrical stimulation purposes. Therefore, future experiments with the graphene nanoplatelets-based hydrogels will focus on electrodes for biosensors and extracellular recordings of neurons or cardiac myocytes. KW - Hydrogel KW - Biosensor KW - Alginate Y1 - 2022 U6 - https://doi.org/https://doi.org/10.1016/j.bea.2022.100045 VL - 2022 IS - 4 SP - 1 EP - 2 ER - TY - THES A1 - Belle, Stefan T1 - Herstellung und Charakterisierung von homogenen und inhomogenen Hohlwellenleitern zur Polarisationsänderung KW - Hohlleiter Y1 - 2022 ER - TY - JOUR A1 - Belle, Stefan A1 - Scheurich, Steffen A1 - Hellmann, Ralf A1 - So, Sik A1 - Sparrow, Ian A1 - Emmerson, Greg T1 - Refractive index sensing for online monitoring water and ethanol contents in biofuels JF - Sensors KW - Biokraftstoff Y1 - 2014 U6 - https://doi.org/10.1117/12.853849 SN - 1424-8220 IS - 7726 ER - TY - CHAP A1 - Scheurich, Steffen A1 - Belle, Stefan A1 - Hellmann, Ralf A1 - So, Sik A1 - Sparrow, Ian A1 - Emmerson, Greg T1 - Application of a silica-on-silicon planar optical waveguide. Bragg grating sensor for organic liquid compound detection T2 - SPIE Optics an optoelectronics conference, Proceedings of SPIE, Vol. 7356, Prag, CR KW - Bragg-Reflektor KW - Sensor Y1 - 2014 SN - 978-0819476302 IS - 7356 ER - TY - JOUR A1 - Girschikofsky, Maiko A1 - Rosenberger, Manuel A1 - Belle, Stefan A1 - Brutschy, Malte A1 - Waldvogel, Siegfried A1 - Hellmann, Ralf T1 - Highly sensitive detection of naphthalene in solvent vapor using a functionalized PBG refractive index sensor JF - Sensors KW - Bragg-Reflektor KW - Sensor Y1 - 2014 U6 - https://doi.org/10.3390/s120202018 VL - 12 IS - 2 SP - 2018 EP - 2025 ER - TY - JOUR A1 - Girschikofsky, Maiko A1 - Rosenberger, Manuel A1 - Belle, Stefan A1 - Brutschy, Malte A1 - Waldvogel, Siegfried A1 - Hellmann, Ralf T1 - Optical planar bragg grating sensor for real-time detection of benzene, toluene und xylene in solvent vapour JF - Sensors & Actuators, B - Chemical KW - Bragg-Reflektor Y1 - 2014 VL - 171/172 IS - 8/9 SP - 338 EP - 342 ER - TY - CHAP A1 - Scheurich, Steffen A1 - Belle, Stefan A1 - Hellmann, Ralf A1 - So, Sik A1 - Sparrow, Ian A1 - Emmerson, Greg T1 - Planar optical waveguide bragg grating chemical sensor for online process control T2 - 3rd integrated optics - sensors, sensing structures and methodes Korbielow, PL KW - Bragg-Reflektor KW - Sensor Y1 - 2014 ER -