@article{YoshinobuMiyamotoWagneretal.2015, author = {Yoshinobu, Tatsuo and Miyamoto, Ko-ichiro and Wagner, Torsten and Sch{\"o}ning, Michael Josef}, title = {Recent developments of chemical imaging sensor systems based on the principle of the light-addressable potentiometric sensor}, series = {Sensors and actuators B: Chemical}, volume = {207, Part B}, journal = {Sensors and actuators B: Chemical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-3077 (E-Journal); 0925-4005 (Print)}, doi = {10.1016/j.snb.2014.09.002}, pages = {926 -- 932}, year = {2015}, abstract = {The light-addressable potentiometric sensor (LAPS) is an electrochemical sensor with a field-effect structure to detect the variation of the Nernst potential at its sensor surface, the measured area on which is defined by illumination. Thanks to this light-addressability, the LAPS can be applied to chemical imaging sensor systems, which can visualize the two-dimensional distribution of a particular target ion on the sensor surface. Chemical imaging sensor systems are expected to be useful for analysis of reaction and diffusion in various electrochemical and biological samples. Recent developments of LAPS-based chemical imaging sensor systems, in terms of the spatial resolution, measurement speed, image quality, miniaturization and integration with microfluidic devices, are summarized and discussed.}, language = {en} } @article{GuoMiyamotoWagneretal.2014, author = {Guo, Yuanyuan and Miyamoto, Ko-ichiro and Wagner, Torsten and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {Device simulation of the light-addressable potentiometric sensor for the investigation of the spatial resolution}, series = {Sensors and actuators B: Chemical}, volume = {204}, journal = {Sensors and actuators B: Chemical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-3077 (E-Journal); 0925-4005 (Print)}, doi = {10.1016/j.snb.2014.08.016}, pages = {659 -- 665}, year = {2014}, abstract = {As a semiconductor-based electrochemical sensor, the light-addressable potentiometric sensor (LAPS) can realize two dimensional visualization of (bio-)chemical reactions at the sensor surface addressed by localized illumination. Thanks to this imaging capability, various applications in biochemical and biomedical fields are expected, for which the spatial resolution is critically significant. In this study, therefore, the spatial resolution of the LAPS was investigated in detail based on the device simulation. By calculating the spatiotemporal change of the distributions of electrons and holes inside the semiconductor layer in response to a modulated illumination, the photocurrent response as well as the spatial resolution was obtained as a function of various parameters such as the thickness of the Si substrate, the doping concentration, the wavelength and the intensity of illumination. The simulation results verified that both thinning the semiconductor substrate and increasing the doping concentration could improve the spatial resolution, which were in good agreement with known experimental results and theoretical analysis. More importantly, new findings of interests were also obtained. As for the dependence on the wavelength of illumination, it was found that the known dependence was not always the case. When the Si substrate was thick, a longer wavelength resulted in a higher spatial resolution which was known by experiments. When the Si substrate was thin, however, a longer wavelength of light resulted in a lower spatial resolution. This finding was explained as an effect of raised concentration of carriers, which reduced the thickness of the space charge region. The device simulation was found to be helpful to understand the relationship between the spatial resolution and device parameters, to understand the physics behind it, and to optimize the device structure and measurement conditions for realizing higher performance of chemical imaging systems.}, language = {en} } @article{GuoSekiMiyamotoetal.2014, author = {Guo, Yuanyuan and Seki, Kosuke and Miyamoto, Ko-ichiro and Wagner, Torsten and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {Novel photoexcitation method for light-addressable potentiometric sensor with higher spatial resolution}, series = {Applied physics express : APEX}, volume = {7}, journal = {Applied physics express : APEX}, number = {6}, publisher = {IOP}, address = {Bristol}, issn = {1882-0786 (E-Journa); 1882-0778 (Print)}, doi = {10.7567/APEX.7.067301}, pages = {067301-4}, year = {2014}, abstract = {A novel photoexcitation method for the light-addressable potentiometric sensor (LAPS) is proposed to achieve a higher spatial resolution of chemical images. The proposed method employs a combined light source that consists of a modulated light probe, which generates the alternating photocurrent signal, and a ring of constant illumination surrounding it. The constant illumination generates a sheath of carriers with increased concentration which suppresses the spread of photocarriers by enhanced recombination. A device simulation was carried out to verify the effect of constant illumination on the spatial resolution, which demonstrated that a higher spatial resolution can be obtained.}, language = {en} } @article{MiyamotoItabashiWagneretal.2014, author = {Miyamoto, Ko-ichiro and Itabashi, Akinori and Wagner, Torsten and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {High-speed chemical imaging inside a microfluidic channel}, series = {Sensors and actuators. B: Chemical}, volume = {194}, journal = {Sensors and actuators. B: Chemical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-3077 (E-Journal); 0925-4005 (Print)}, doi = {10.1016/j.snb.2013.12.090}, pages = {521 -- 527}, year = {2014}, abstract = {In this study, a high-speed chemical imaging system was developed for visualization of the interior of a microfluidic channel. A microfluidic channel was constructed on the sensor surface of the light-addressable potentiometric sensor (LAPS), on which the ion concentrations could be measured in parallel at up to 64 points illuminated by optical fibers. The temporal change of pH distribution inside the microfluidic channel was recorded at a maximum rate of 100 frames per second (fps). The high frame rate allowed visualization of moving interfaces and plugs in the channel even at a flow velocity of 111 mm/s, which suggests the feasibility of plug-based microfluidic devices for flow-injection analysis (FIA).}, language = {en} } @article{MiyamotoHirayamaWagneretal.2013, author = {Miyamoto, Ko-ichiro and Hirayama, Yuji and Wagner, Torsten and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {Visualization of enzymatic reaction in a microfluidic channel using chemical imaging sensor}, series = {Electrochimica acta}, journal = {Electrochimica acta}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-3859 (E-Journal); 0013-4686 (Print)}, pages = {Publ. online}, year = {2013}, language = {en} } @article{MiyamotoIchimuraWagneretal.2013, author = {Miyamoto, Ko-ichiro and Ichimura, Hiroki and Wagner, Torsten and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {Chemical imaging of the concentration profile of ion diffusion in a microfluidic channel}, series = {Sensors and actuators. B: Chemical}, volume = {189}, journal = {Sensors and actuators. B: Chemical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-3077 (E-Journal); 0925-4005 (Print)}, doi = {10.1016/j.snb.2013.04.057}, pages = {240 -- 245}, year = {2013}, abstract = {The chemical imaging sensor is a device to visualize the spatial distribution of chemical species based on the principle of LAPS (light-addressable potentiometric sensor), which is a field-effect chemical sensor based on semiconductor. In this study, the chemical imaging sensor has been applied to investigate the ion profile of laminar flows in a microfluidic channel. The chemical images (pH maps) were collected in a Y-shaped microfluidic channel while injecting HCl and NaCl solutions into two branches. From the chemical images, it was clearly observed that the injected solutions formed laminar flows in the channel. In addition, ion diffusion across the laminar flows was observed, and the diffusion coefficient could be derived by fitting the pH profiles to the Fick's equation.}, language = {en} } @article{WernerWagnerYoshinobuetal.2013, author = {Werner, Frederik and Wagner, Torsten and Yoshinobu, Tatsuo and Keusgen, Michael and Sch{\"o}ning, Michael Josef}, title = {Frequency behaviour of light-addressable potentiometric sensors}, series = {Physica Status Solidi (A)}, volume = {210}, journal = {Physica Status Solidi (A)}, number = {5}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1521-396X ; 0031-8965}, doi = {10.1002/pssa.201200929}, pages = {884 -- 891}, year = {2013}, abstract = {Light-addressable potentiometric sensors (LAPS) are semiconductor-based potentiometric sensors, with the advantage to detect the concentration of a chemical species in a liquid solution above the sensor surface in a spatially resolved manner. The addressing is achieved by a modulated and focused light source illuminating the semiconductor and generating a concentration-depending photocurrent. This work introduces a LAPS set-up that is able to monitor the electrical impedance in addition to the photocurrent. The impedance spectra of a LAPS structure, with and without illumination, as well as the frequency behaviour of the LAPS measurement are investigated. The measurements are supported by electrical equivalent circuits to explain the impedance and the LAPS-frequency behaviour. The work investigates the influence of different parameters on the frequency behaviour of the LAPS. Furthermore, the phase shift of the photocurrent, the influence of the surface potential as well as the changes of the sensor impedance will be discussed.}, language = {en} } @article{ItabashiKosakaMiyamotoetal.2013, author = {Itabashi, Akinori and Kosaka, Naoki and Miyamoto, Ko-ichiro and Wagner, Torsten and Sch{\"o}ning, Michael Josef}, title = {High-speed chemical imaging system based on front-side-illuminated LAPS}, series = {Sensors and actuators B: Chemical}, volume = {182}, journal = {Sensors and actuators B: Chemical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-3077}, doi = {10.1016/j.snb.2013.03.016}, pages = {315 -- 321}, year = {2013}, abstract = {The chemical imaging sensor is a semiconductor-based chemical sensor that can visualize the spatial distribution of specific ions on the sensing surface. The conventional chemical imaging system based on the light-addressable potentiometric sensor (LAPS), however, required a long time to obtain a chemical image, due to the slow mechanical scan of a single light beam. For high-speed imaging, a plurality of light beams modulated at different frequencies can be employed to measure the ion concentrations simultaneously at different locations on the sensor plate by frequency division multiplex (FDM). However, the conventional measurement geometry of back-side illumination limited the bandwidth of the modulation frequency required for FDM measurement, because of the low-pass filtering characteristics of carrier diffusion in the Si substrate. In this study, a high-speed chemical imaging system based on front-side-illuminated LAPS was developed, which achieved high-speed spatiotemporal recording of pH change at a rate of 70 frames per second.}, language = {en} } @article{MiyamotoIchimuraWagneretal.2012, author = {Miyamoto, K. and Ichimura, H. and Wagner, Torsten and Yoshinobu, T. and Sch{\"o}ning, Michael Josef}, title = {Chemical Imaging of ion Diffusion in a Microfluidic Channel}, series = {Procedia Engineering}, journal = {Procedia Engineering}, number = {47}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2012.09.289}, pages = {886 -- 889}, year = {2012}, abstract = {The chemical imaging sensor is a chemical sensor which is capable of visualizing the spatial distribution of chemical species in sample solution. In this study, a novel measurement system based on the chemical imaging sensor was developed to observe the inside of a Y-shaped microfluidic channel while injecting two sample solutions from two branches. From the collected chemical images, it was clearly observed that the injected solutions formed laminar flows in the microfluidic channel. In addition, ion diffusion across the laminar flows was observed. This label-free method can acquire quantitative data of ion distribution and diffusion in microfluidic devices, which can be used to determine the diffusion coefficients, and therefore, the molecular weights of chemical species in the sample solution.}, language = {en} } @article{WagnerShigiaharaMiyamotoetal.2012, author = {Wagner, Torsten and Shigiahara, N. and Miyamoto, K. and Suzurikawa, J. and Finger, F. and Sch{\"o}ning, Michael Josef and Yoshinobu, T.}, title = {Light-addressable Potentiometric Sensors and Light-addressable Electrodes as a Combined Sensor-and-manipulator Microsystem with High Flexibility}, series = {Procedia Engineering}, journal = {Procedia Engineering}, number = {47}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2012.09.290}, pages = {890 -- 893}, year = {2012}, abstract = {This work describes the novel combination of the light-addressable electrode (LAE) and the light-addressable potentiometric sensor (LAPS) into a microsystem set-up. Both the LAE as well as the LAPS shares the principle of addressing the active spot by means of a light beam. This enables both systems to manipulate resp. to detect an analyte with a high spatial resolution. Hence, combining both principles into a single set-up enables the active stimulation e.g., by means of electrolysis and a simultaneous observation e.g., the response of an entrapped biological cell by detection of extracellular pH changes. The work will describe the principles of both technologies and the necessary steps to integrate them into a single set-up. Furthermore, examples of application and operation of such systems will be presented.}, language = {en} } @article{MiyamotoKanekoMatsuoetal.2012, author = {Miyamoto, Ko-ichiro and Kaneko, Kazumi and Matsuo, Akira and Wagner, Torsten and Kanoh, Shin{\´i}chiro and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {Miniaturized chemical imaging sensor system using an OLED display panel}, series = {Sensors and Actuators B: Chemical}, volume = {170}, journal = {Sensors and Actuators B: Chemical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0925-4005}, doi = {10.1016/j.snb.2011.02.029}, pages = {82 -- 87}, year = {2012}, abstract = {The chemical imaging sensor is a semiconductor-based chemical sensor that can visualize the two-dimensional distribution of specific ions or molecules in the solution. In this study, we developed a miniaturized chemical imaging sensor system with an OLED display panel as a light source that scans the sensor plate. In the proposed configuration, the display panel is placed directly below the sensor plate and illuminates the back surface. The measured area defined by illumination can be arbitrarily customized to fit the size and the shape of the sample to be measured. The waveform of the generated photocurrent, the current-voltage characteristics and the pH sensitivity were investigated and pH imaging with this miniaturized system was demonstrated.}, language = {en} } @inproceedings{YoshinobuMiyamotoWagneretal.2012, author = {Yoshinobu, Tatsuo and Miyamoto, Ko-Ichiro and Wagner, Torsten and Sch{\"o}ning, Michael Josef}, title = {Miniaturized and high-speed chemical imaging systems}, series = {Nano-Biomedical Engineering 2012. Proceedings of the Tohoku University Global Centre of Excellence Programme, Sakura Hall, Tohoku University, Sendai Japan, 5 - 6 March 2012}, booktitle = {Nano-Biomedical Engineering 2012. Proceedings of the Tohoku University Global Centre of Excellence Programme, Sakura Hall, Tohoku University, Sendai Japan, 5 - 6 March 2012}, editor = {Yamaguchi, Takami}, publisher = {World Scientific}, address = {Singapur}, doi = {10.1142/9781848169067_0045}, pages = {386 -- 395}, year = {2012}, language = {en} } @article{WagnerMiyamotoShigiharaetal.2011, author = {Wagner, Torsten and Miyamoto, Ko-ichiro and Shigihara, Noriko and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {Microfluidic systems with free definable sensor spots by an integrated light-addressable potentiometric sensor}, series = {Procedia Engineering. 25 (2011)}, journal = {Procedia Engineering. 25 (2011)}, publisher = {Elsevier}, address = {Amsterdam}, isbn = {1877-7058}, pages = {791 -- 794}, year = {2011}, language = {en} } @article{WernerWagnerMiyamotoetal.2011, author = {Werner, Frederik and Wagner, Torsten and Miyamoto, Ko-ichiro and Yoshinobu, Tatsuo and Sch{\"o}ning, Michael Josef}, title = {High speed and high resolution chemical imaging based on a new type of OLED-LAPS set-up}, series = {Procedia Engineering. 25 (2011)}, journal = {Procedia Engineering. 25 (2011)}, publisher = {Elsevier}, address = {Amsterdam}, isbn = {1877-7058}, pages = {346 -- 349}, year = {2011}, language = {en} } @article{WagnerMiyamotoWerneretal.2011, author = {Wagner, Torsten and Miyamoto, K. and Werner, Frederik and Sch{\"o}ning, Michael Josef and Yoshinobu, T.}, title = {Flexible electrochemical imaging with "zoom-in" functionality by using a new type of light-addressable potentiometric sensor}, publisher = {IEEE}, address = {New York}, pages = {2133 -- 2135}, year = {2011}, language = {en} } @article{MiyamotoWagnerSchoeningetal.2011, author = {Miyamoto, K. and Wagner, Torsten and Sch{\"o}ning, Michael Josef and Yoshinobu, T.}, title = {Multi-well structure for cell culture on the chemical imaging sensor}, publisher = {IEEE}, address = {New York}, pages = {2130 -- 2132}, year = {2011}, language = {en} } @article{WernerGroebelWagneretal.2011, author = {Werner, Frederik and Groebel, Simone and Wagner, Torsten and Yoshinobu, Tatsuo and Selmer, Thorsten and Baumann, Marcus and Sch{\"o}ning, Michael Josef}, title = {{\"U}berwachung der metabolischen Aktivit{\"a}t von Mikroorganismen zur Kontrolle des biologischen Prozesses im Biogasfermenter}, series = {Biogas 2011 : Energietr{\"a}ger der Zukunft ; 6. Fachtagung, Fachtagung Braunschweig, 08. und 09. Juni 2011 / VDI Energie und Umwelt}, journal = {Biogas 2011 : Energietr{\"a}ger der Zukunft ; 6. Fachtagung, Fachtagung Braunschweig, 08. und 09. Juni 2011 / VDI Energie und Umwelt}, publisher = {VDI-Verl.}, address = {D{\"u}sseldorf}, isbn = {978-3-18-092121-1}, pages = {285 -- 286}, year = {2011}, language = {de} } @article{ReisertGeisslerFlorkeetal.2011, author = {Reisert, Steffen and Geissler, H. and Florke, R. and Wagner, P. and Wagner, Torsten and Sch{\"o}ning, Michael Josef}, title = {Controlling aseptic sterilization processes by means of a multi-sensor system}, publisher = {IEEE}, address = {New York}, pages = {18 -- 22}, year = {2011}, language = {en} } @article{MiyamotoKanekoMatsuoetal.2010, author = {Miyamoto, Ko-ichiro and Kaneko, Kazumi and Matsuo, Akira and Wagner, Torsten and Kanoh, Shin`ichiro and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {Miniaturized chemical imaging sensor system using an OLED display panel}, series = {Procedia Engineering. 5 (2010)}, journal = {Procedia Engineering. 5 (2010)}, isbn = {1877-7058}, pages = {516 -- 519}, year = {2010}, language = {en} } @article{WagnerMiyamotoSchoeningetal.2010, author = {Wagner, Torsten and Miyamoto, Ko-ichiro and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {Novel combination of digital light processing (DLP) and light-addressable potentiometric sensors (LAPS) for flexible chemical imaging}, series = {Procedia Engineering. 5 (2010)}, journal = {Procedia Engineering. 5 (2010)}, isbn = {1877-7058}, pages = {520 -- 523}, year = {2010}, language = {en} }