@inproceedings{KeferRosenbergerHessleretal.2020, author = {Kefer, Stefan and Rosenberger, Manuel and Hessler, Steffen and Girschikofsky, Maiko and Belle, Stefan and Roth, Gian-Luca and Schmauß, Bernhard and Hellmann, Ralf}, title = {Fabrication and Applications of Polymer Planar Bragg Grating Sensors based on Cyclic Olefin Copolymers}, series = {2019 Photonics \& Electromagnetics Research Symposium - Fall (PIERS - Fall)}, booktitle = {2019 Photonics \& Electromagnetics Research Symposium - Fall (PIERS - Fall)}, publisher = {Institute of Electrical and Electronics Engineers}, isbn = {978-1-7281-5304-9}, doi = {10.1109/PIERS-Fall48861.2019.9021801}, pages = {647 -- 655}, year = {2020}, abstract = {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.}, subject = {Optischer Sensor}, language = {en} } @article{KoerbitzerKraussBelleetal.2019, author = {K{\"o}rbitzer, Berit Silke and Krauß, Peter and Belle, Stefan and Schneider, J{\"o}rg and Thielemann, Christiane}, title = {Electrochemical Characterization of Graphene Microelectrodes for Biological Applications}, series = {ChemNanoMat}, volume = {2019}, journal = {ChemNanoMat}, number = {5:4}, doi = {10.1002/cnma.201800652}, pages = {427 -- 435}, year = {2019}, abstract = {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.}, subject = {Mikroelektrode}, language = {en} } @inproceedings{NickHockEmmerichetal.2015, author = {Nick, Christoph and Hock, Christina and Emmerich, Florian and Belle, Stefan and Thielemann, Christiane and Asmus, Tim and Loose, Thomas and Wienand, Karlheinz}, title = {Ultrathin gold as sensor platform for biomolecules}, series = {2015 International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO), Changchun, China}, booktitle = {2015 International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO), Changchun, China}, doi = {10.1109/3M-NANO.2015.7425462}, year = {2015}, abstract = {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.}, subject = {Biosensor}, language = {en} } @article{FlachsEtzelMayeretal.2022, author = {Flachs, Dennis and Etzel, Johannes and Mayer, Margot and Harbecke, Frederic and Belle, Stefan and Rickmeyer, Tim and Thielemann, Christiane}, title = {Characterization of electrically conductive, printable ink based on alginate hydrogel and graphene nanoplatelets}, series = {Biomedical Engineering Advances}, volume = {2022}, journal = {Biomedical Engineering Advances}, number = {4}, doi = {https://doi.org/10.1016/j.bea.2022.100045}, pages = {1 -- 2}, year = {2022}, abstract = {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.}, subject = {Hydrogel}, language = {en} } @phdthesis{Belle2022, author = {Belle, Stefan}, title = {Herstellung und Charakterisierung von homogenen und inhomogenen Hohlwellenleitern zur Polarisations{\"a}nderung}, school = {Technische Hochschule Aschaffenburg}, year = {2022}, subject = {Hohlleiter}, language = {de} } @article{BelleScheurichHellmannetal.2010, author = {Belle, Stefan and Scheurich, Steffen and Hellmann, Ralf and So, Sik and Sparrow, Ian and Emmerson, Greg}, title = {Refractive index sensing for online monitoring water and ethanol contents in biofuels}, series = {Sensors}, journal = {Sensors}, number = {7726}, issn = {1424-8220}, doi = {10.1117/12.853849}, year = {2010}, subject = {Biokraftstoff}, language = {en} } @inproceedings{ScheurichBelleHellmannetal.2009, author = {Scheurich, Steffen and Belle, Stefan and Hellmann, Ralf and So, Sik and Sparrow, Ian and Emmerson, Greg}, title = {Application of a silica-on-silicon planar optical waveguide. Bragg grating sensor for organic liquid compound detection}, series = {SPIE Optics an optoelectronics conference, Proceedings of SPIE, Vol. 7356, Prag, CR}, booktitle = {SPIE Optics an optoelectronics conference, Proceedings of SPIE, Vol. 7356, Prag, CR}, number = {7356}, isbn = {978-0819476302}, year = {2009}, subject = {Bragg-Reflektor}, language = {en} } @article{GirschikofskyRosenbergerBelleetal.2011, author = {Girschikofsky, Maiko and Rosenberger, Manuel and Belle, Stefan and Brutschy, Malte and Waldvogel, Siegfried and Hellmann, Ralf}, title = {Highly sensitive detection of naphthalene in solvent vapor using a functionalized PBG refractive index sensor}, series = {Sensors}, volume = {12}, journal = {Sensors}, number = {2}, doi = {10.3390/s120202018}, pages = {2018 -- 2025}, year = {2011}, subject = {Bragg-Reflektor}, language = {en} } @article{GirschikofskyRosenbergerBelleetal.2011, author = {Girschikofsky, Maiko and Rosenberger, Manuel and Belle, Stefan and Brutschy, Malte and Waldvogel, Siegfried and Hellmann, Ralf}, title = {Optical planar bragg grating sensor for real-time detection of benzene, toluene und xylene in solvent vapour}, series = {Sensors \& Actuators, B - Chemical}, volume = {171/172}, journal = {Sensors \& Actuators, B - Chemical}, number = {8/9}, pages = {338 -- 342}, year = {2011}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{ScheurichBelleHellmannetal.2009, author = {Scheurich, Steffen and Belle, Stefan and Hellmann, Ralf and So, Sik and Sparrow, Ian and Emmerson, Greg}, title = {Planar optical waveguide bragg grating chemical sensor for online process control}, series = {3rd integrated optics - sensors, sensing structures and methodes Korbielow, PL}, booktitle = {3rd integrated optics - sensors, sensing structures and methodes Korbielow, PL}, year = {2009}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{BelleScheurichHellmann2009, author = {Belle, Stefan and Scheurich, Steffen and Hellmann, Ralf}, title = {Interrogation water content in organic solvents by planar bragg grating sensors}, series = {Proceedings SENSOR}, booktitle = {Proceedings SENSOR}, number = {Vol. II, P3.2}, isbn = {978-3-9810993-6-2}, pages = {324 -- 329}, year = {2009}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{RosenbergerBelleHellmann2009, author = {Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Optical interrogation of bragg grating sensors using tunable fibre based bandpass filter}, series = {Proceedings of the 20st international science conference, Mittweida}, booktitle = {Proceedings of the 20st international science conference, Mittweida}, year = {2009}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{RosenbergerBelleHellmann2011, author = {Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Detection of biochemical reaction and DNA hybridization using a planar bragg grating sensor}, series = {Proceeding SPIE, Vol. 8073, article id: 80730C}, booktitle = {Proceeding SPIE, Vol. 8073, article id: 80730C}, number = {8073}, doi = {10.1117/12.886785}, year = {2011}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{RosenbergerBelleHellmann2011, author = {Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Detection of unlabeled DNA hybridization with a planar bragg grating sensor}, series = {Proceeding XXV microCAD, International scientific conference, 2011, Section R}, booktitle = {Proceeding XXV microCAD, International scientific conference, 2011, Section R}, pages = {67 -- 72}, year = {2011}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{RosenbergerBelleHellmann2011, author = {Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Optical interrogation of chemical and temperature bragg grating sensors using tunable fiber coupled bandpass filter}, series = {Proceeding XXV microCAD, International scientific conference, 2011, Section H}, booktitle = {Proceeding XXV microCAD, International scientific conference, 2011, Section H}, pages = {25 -- 30}, year = {2011}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{RosenbergerBelleHellmann2011, author = {Rosenberger, Markus and Belle, Stefan and Hellmann, Ralf}, title = {Detection of unlabeled DNA hybridization with a planar Bragg Grating Sensor}, series = {XXV International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, booktitle = {XXV International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, number = {Section R}, pages = {67 -- 72}, year = {2011}, subject = {Bragg-Reflektor}, language = {en} } @article{BelleRosenbergerHellmann2011, author = {Belle, Stefan and Rosenberger, Manuel and Hellmann, Ralf}, title = {Evanescent wave planar bragg grating sensor for real-time detection of unlabelled biomolecules}, series = {Optics Express}, journal = {Optics Express}, year = {2011}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{BelleRosenbergerHellmann2011, author = {Belle, Stefan and Rosenberger, Manuel and Hellmann, Ralf}, title = {Optical fibre sensing in the production process and storage of biofuels}, series = {Proceeding XXV microCAD, International scientific conference, 2011, Section A}, booktitle = {Proceeding XXV microCAD, International scientific conference, 2011, Section A}, pages = {21 -- 26}, year = {2011}, subject = {Biokraftstoff}, language = {en} } @article{FlachsZhukovZechetal.2024, author = {Flachs, Dennis and Zhukov, Sergey and Zech, Isabella and Schreck, Timo and Belle, Stefan and von Seggern, Heiinz and Kupnik, Mario and Altmann, Alexander Anton and Thielemann, Christiane}, title = {Enzymatic Self-Degradable PLA-Based Electrets}, series = {Journal of Polymers and the Environment}, volume = {2024}, journal = {Journal of Polymers and the Environment}, number = {1}, doi = {Journal of https://doi.org/10.1007/s10924-024-03240-6}, pages = {1 -- 11}, year = {2024}, abstract = {In recent years, the demand for sustainable and degradable materials and electronic devices has increased significantly. Among a range of biodegradable polymers, poly(lactic acid) (PLA) is a good alternative to conventional petrol-based polymers because of its attractive mechanical properties and its easy processability. Recently, PLA has also been described as a promising dielectric material with piezoelectric and electret properties. We expect that PLA—after further optimization— will play an important role as a material for environmentally friendly sensors in the future, where first applications such as air filters and pressure sensors have already been proposed. However, degradation under normal ambient conditions is very slow, and an accelerated and controllable degradation process is highly desirable for any type of PLA-based sensors. Enzymatic hydrolysis with embedded enzymes has been proposed as an approach to accelerate and control degradation. In this work, we investigate the properties of PLA in terms of dielectric and mechanical properties with a focus on its ability to store charges after the enzyme proteinase K (Trit. album) has been incorporated. Results reveal that proteinase K has a positive effect on the charge stability of solvent-cast PLA electrets after complete evaporation of the solvent. Furthermore, we observed a concentration-dependent acceleration of mass loss in a Tris-HCl buffer. A fast degradation within only one day occurred at a concentration of 6 wt\% proteinase K.}, subject = {Biologisch abbaubarer Kunststoff}, language = {en} } @inproceedings{GirschikofskyRosenbergerBelleetal.2012, author = {Girschikofsky, Maiko and Rosenberger, Manuel and Belle, Stefan and Brutschy, Malte and Waldvogel, Siegfried and Hellmann, Ralf}, title = {α-Cyclodextrin functionalized planar Bragg grating sensor for the detection of small arene traces in solvamt vapour}, series = {14th international meeting on chemical sensors (IMCS 2012)}, booktitle = {14th international meeting on chemical sensors (IMCS 2012)}, isbn = {978-3-9813484-2-2}, doi = {10.5162/IMCS2012/7.5.1}, pages = {646 -- 648}, year = {2012}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{GirschikofskyRosenbergerBelleetal.2012, author = {Girschikofsky, Maiko and Rosenberger, Manuel and Belle, Stefan and Brutschy, Malte and Waldvogel, Siegfried and Waldvogel, Ralf}, title = {Functionalized planar Bragg grating sensor for the detection of BTX in solvent vapour}, series = {Proceedings of SPIE 8439, Optical Sensing and Detection II, 843916}, booktitle = {Proceedings of SPIE 8439, Optical Sensing and Detection II, 843916}, number = {8439}, doi = {10.1117/12.921078}, year = {2012}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{KollerHesslerRosenbergeretal.2012, author = {Koller, Georg and Hessler, Steffen and Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Micro-structured optical waveguide fabrication in PMMA using low frequency reactive ion etching}, series = {Proceedings of the XXVI International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, booktitle = {Proceedings of the XXVI International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, year = {2012}, subject = {Wellenleiter}, language = {en} } @inproceedings{GirschikofskyRosenbergerBelleetal.2012, author = {Girschikofsky, Maiko and Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Surface modifications of planar bragg grating refractive index sensors for gas detection}, series = {Proceedings of the XXVI International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, booktitle = {Proceedings of the XXVI International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, year = {2012}, subject = {Bragg-Reflektor}, language = {en} }