TY - JOUR A1 - Nick, Christoph A1 - Yadav, Sandeep A1 - Joshi, Ravi A1 - Schneider, Jörg A1 - Thielemann, Christiane T1 - A three-dimensional microelectrode array composed of vertically aligned ultra-dense carbon nanotube networks JF - Applied Physics Letters N2 - Electrodes based on carbon nanotubes are a promising approach to manufacture highly sensitive sensors with a low limit of signal detection and a high signal-to-noise ratio. This is achieved by dramatically increasing the electrochemical active surface area without increasing the overall geometrical dimensions. Typically, carbon nanotube electrodes are nearly planar and composed of randomly distributed carbon nanotube networks having a limited surface gain for a specific geometrical surface area. To overcome this limitation, we have introduced vertically aligned carbon nanotube (VACNT) networks as electrodes, which are arranged in a microelectrode pattern of 60 single electrodes. Each microelectrode features a very high aspect ratio of more than 300 and thus a dramatically increased surface area. These microelectrodes composed of VACNT networks display dramatically decreased impedance over the entire frequency range compared to planar microelectrodes caused by the enormous capacity increase. This is experimentally verified by electrochemical impedance spectroscopy and cyclic voltammetry. KW - Microelectrode arrays KW - Electrochemical impedance spectroscopy KW - Chemical compounds and components KW - Electrolytes KW - Signal processing KW - Mikroelektrode KW - Array KW - Kohlenstoff-Nanoröhre Y1 - 2015 U6 - https://doi.org/10.1063/1.4926330 VL - 2015 IS - 107 SP - 1 EP - 1 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 - CHAP A1 - Emmerich, Florian A1 - Thielemann, Christiane T1 - Patterning of PMMA by gold-nanoparticle initiated localized decomposition T2 - 2015 International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO), Changchun, China N2 - The need for manipulating matter at its smallest scale has been a hot topic in research for the last decades. As the final goal of arranging single atoms has been achieved, research focuses on two targets: firstly, improving the capabilities of existing technologies towards nanometer resolution and secondly, finding new methods for producing nanostructures in a fast and easy way. Here, we present a new maskless method for sub-micro-patterning of poly(methyl methacrylate) (PMMA) thin films. By applying atomic-force-microscope (AFM) assisted nano-xerography, electric charges were locally injected with an AFM-tip into PMMA. The resulting electrostatic patterns attracted charged gold-nanoparticles, which were selectively deposited onto the PMMA layers with lateral dimensions below 200 nm. In a second step, heat treatment at 275 °C initiated a selective decomposition of the PMMA layer, only observed in PMMA-areas covered with nanoparticles, whereas uncovered areas were not modified by the heat treatment. Analyzing the grooves with the AFM, we found that lines with a width in the sub-micrometer range to several micrometers have successfully been realized. We propose this new and promising method to manufacture nano-grooves used as masking for lift-off processes, for functionalization of underlying areas, or for micro-contact-printing. KW - Nanoparticles KW - Gold KW - Thermal stability KW - Heating KW - Electrostatics KW - Polymethylmethacrylate KW - Dünnschichttechnik Y1 - 2015 U6 - https://doi.org/10.1109/3M-NANO.2015.7425480 ER - TY - JOUR A1 - Nick, Christoph A1 - Schlaak, Helmut A1 - Thielemann, Christiane T1 - Simulation and Measurement of Neuroelectrodes' Characteristics with Integrated High Aspect Ratio Nano Structures JF - AIMS Journal N2 - Improving the interface between electrodes and neurons has been the focus of research for the last decade. Neuroelectrodes should show small geometrical surface area and low impedance for measuring and high charge injection capacities for stimulation. Increasing the electrochemically active surface area by using nanoporous electrode material or by integrating nanostructures onto planar electrodes is a common approach to improve this interface. In this paper a simulation approach for neuro electrodes' characteristics with integrated high aspect ratio nano structures based on a point-contact-model is presented. The results are compared with experimental findings conducted with real nanostructured microelectrodes. In particular, effects of carbon nanotubes and gold nanowires integrated onto microelectrodes are described. Simulated and measured impedance properties are presented and its effects onto the transfer function between the neural membrane potential and the amplifier output signal are studied based on the point-contact-model. Simulations show, in good agreement with experimental results, that electrode impedances can be dramatically reduced by the integration of high aspect ratio nanostructures such as gold nanowires and carbon nanotubes. This lowers thermal noise and improves the signal-to-noise ratio for measuring electrodes. It also may increase the adhesion of cells to the substrate and thus increase measurable signal amplitudes. KW - Neuronales Netz KW - Mikroelektrode Y1 - 2015 U6 - https://doi.org/10.3934/matersci.2015.3.189 VL - 2015 IS - 2 SP - 189 EP - 202 ER - TY - JOUR A1 - Frieß, Johannes A1 - Heselich, Anja A1 - Ritter, Sylvia A1 - Haber, Angelina A1 - Kaiser, Nicole A1 - Layer, Paul A1 - Thielemann, Christiane T1 - Electrophysiologic and cellular characteristics of cardiomyocytes after X-ray irradiation JF - Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis KW - Herzmuskelzelle KW - Röntgenbestrahlung Y1 - 2015 VL - 2015 IS - 777 SP - 1 EP - 10 ER - TY - CHAP A1 - Körbitzer, Berit Silke A1 - Krauß, Peter A1 - Nick, Christoph A1 - Schneider, Jörg A1 - Thielemann, Christiane T1 - Graphene electrodes for recording and stimulation of neural cells T2 - ICREA Workshop on Graphene Nanobiosensors KW - Nervenzelle KW - Elektrostimulation Y1 - 2015 CY - Barcelona, Spanien ER - TY - RPRT A1 - Mayer, Margot A1 - Arrizabalaga, Onetsine A1 - Ritter, Sylvia A1 - Thielemann, Christiane T1 - Human embryonic stem cell derived neurospheres form functional networks on microelectrode arrays T2 - GSI Scientific Report 2015 KW - Embryonale Stammzelle KW - Mikroelektrode KW - Array Y1 - 2015 U6 - https://doi.org/10.15120/GR-2016-1 VL - 2015 IS - GSI Report 2016-1 SP - 205 EP - 205 ER -