TY - CHAP A1 - Yoshinobu, Tatsuo A1 - Krause, Steffi A1 - Miyamoto, Ko-ichiro A1 - Werner, Frederik A1 - Poghossian, Arshak A1 - Wagner, Torsten A1 - Schöning, Michael Josef T1 - (Bio-)chemical Sensing and Imaging by LAPS and SPIM T2 - Label-free biosensing: advanced materials, devices and applications N2 - The light-addressable potentiometric sensor (LAPS) and scanning photo-induced impedance microscopy (SPIM) are two closely related methods to visualise the distributions of chemical species and impedance, respectively, at the interface between the sensing surface and the sample solution. They both have the same field-effect structure based on a semiconductor, which allows spatially resolved and label-free measurement of chemical species and impedance in the form of a photocurrent signal generated by a scanning light beam. In this article, the principles and various operation modes of LAPS and SPIM, functionalisation of the sensing surface for measuring various species, LAPS-based chemical imaging and high-resolution sensors based on silicon-on-sapphire substrates are described and discussed, focusing on their technical details and prospective applications. KW - Chemical imaging KW - Field-effect device KW - Light-addressable potentiometric sensor KW - Potentiometry Y1 - 2018 SN - 978-3-319-75219-8 SP - 103 EP - 132 PB - Springer CY - Cham ER - TY - JOUR A1 - Wagner, Torsten A1 - Werner, Frederik A1 - Miyamoto, Ko-Ichiro A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - A high-density multi-point LAPS set-up using a VCSEL array and FPGA control JF - Sensors and Actuators B: Chemical. 154 (2011), H. 2 Y1 - 2011 SN - 1873-3077 N1 - EUROSENSORS XXIII SP - 124 EP - 128 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Miyamoto, Ko-ichiro A1 - Hayashi, Kosuke A1 - Sakamoto, Azuma A1 - Werner, Frederik A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - A high-Q resonance-mode measurement of EIS capacitive sensor by elimination of series resistance JF - Sensor and Actuators B: Chemical N2 - An EIS capacitive sensor is a semiconductor-based potentiometric sensor, which is sensitive to the ion concentration or pH value of the solution in contact with the sensing surface. To detect a small change in the ion concentration or pH, a small capacitance change must be detected. Recently, a resonance-mode measurement was proposed, in which an inductor was connected to the EIS capacitive sensor and the resonant frequency was correlated with the pH value. In this study, the Q factor of the resonant circuit was enhanced by canceling the internal resistance of the reference electrode and the internal resistance of the inductor coil with the help of a bypass capacitor and a negative impedance converter, respectively. 1% variation of the signal in the developed system corresponded to a pH change of 3.93 mpH, which was about 1/12 of the conventional method, suggesting a better performance in detection of a small pH change. KW - Negative impedance convertor KW - Resonance-mode measurement KW - Chemical sensor KW - EIS capacitive sensor Y1 - 2017 U6 - http://dx.doi.org/10.1016/j.snb.2017.03.002 SN - 0925-4005 VL - 248 SP - 1006 EP - 1010 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Miyamoto, Ko-ichiro A1 - Ichimura, Hiroki A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - Chemical imaging of the concentration profile of ion diffusion in a microfluidic channel JF - Sensors and actuators. B: Chemical N2 - 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. Y1 - 2013 U6 - http://dx.doi.org/10.1016/j.snb.2013.04.057 SN - 1873-3077 (E-Journal); 0925-4005 (Print) N1 - Part of special issue "Selected Papers from the 26th European Conference on Solid-State Transducers" VL - 189 SP - 240 EP - 245 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Miyamoto, Ko-ichiro A1 - Wagner, Torsten A1 - Mimura, Shuhei A1 - Kanoh, Shin`ichiro A1 - Yoshinobu, Tatsuo A1 - Schöning, Michael Josef T1 - Constant-phase-mode operation of the light-addressable potentiometric sensor JF - Procedia Chemistry. 1 (2009), H. 1 Y1 - 2009 SN - 1876-6196 N1 - Proceedings of the Eurosensors XXIII conference ; Eurosensors 23 SP - 1487 EP - 1490 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Miyamoto, Ko-ichiro A1 - Wagner, Torsten A1 - Mimura, Shuhei A1 - Kanoh, Shiníchiro A1 - Yoshinobu, Tatsuo A1 - Schöning, Michael Josef T1 - Constant-phase-mode operation of the light-addressable potentiometric sensor JF - Sensors and Actuators B: Chemical. 154 (2011), H. 2 Y1 - 2011 SN - 1873-3077 N1 - EUROSENSORS XXIII SP - 119 EP - 123 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wagner, Torsten A1 - Werner, Frederik A1 - Miyamoto, Ko-Ichiro A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - Development and characterisation of a compact light-addressable potentiometric sensor (LAPS) based on the digital light processing (DLP) technology for flexible chemical imaging JF - Sensors and Actuators B: Chemical N2 - Chemical imaging systems allow the visualisation of the distribution of chemical species on the sensor surface. This work represents a new flexible approach to read out light-addressable potentiometric sensors (LAPS) with the help of a digital light processing (DLP) set-up. The DLP, known well for video projectors, consists of a mirror-array MEMS device, which allows fast and flexible generation of light patterns. With the help of these light patterns, the sensor surface of the LAPS device can be addressed. The DLP approach has several advantages compared to conventional LAPS set-ups, e.g., the spot size and the shape of the light pointer can be changed easily and no mechanical movement is necessary, which reduces the size of the set-up and increases the stability and speed of the measurement. In addition, the modulation frequency and intensity of the light beam are important parameters of the LAPS set-up. Within this work, the authors will discuss two different ways of light modulation by the DLP set-up, investigate the influence of different modulation frequencies and different light intensities as well as demonstrate the scanning capabilities of the new set-up by pH mapping on the sensor surface. Y1 - 2012 U6 - http://dx.doi.org/10.1016/j.snb.2010.12.003 SN - 0925-4005 N1 - Part of special issue "Eurosensors XXIV, 2010" VL - 170 SP - 34 EP - 39 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Guo, Yuanyuan A1 - Miyamoto, Ko-ichiro A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - Device simulation of the light-addressable potentiometric sensor for the investigation of the spatial resolution JF - Sensors and actuators B: Chemical N2 - 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. Y1 - 2014 U6 - http://dx.doi.org/10.1016/j.snb.2014.08.016 SN - 1873-3077 (E-Journal); 0925-4005 (Print) VL - 204 SP - 659 EP - 665 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Guo, Yuanyuan A1 - Seki, Kosuke A1 - Miyamoto, Ko-ichiro A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - Device simulation of the light-addressable potentiometric sensor with a novel photoexcitation method for a higher spatial resolution JF - Procedia Engineering N2 - A novel photoexcitation method for the light-addressable potentiometric sensor (LAPS) realized a higher spatial resolution of chemical imaging. In this method, a modulated light probe, which generates the alternating photocurrent signal, is surrounded by a ring of constant light, which suppresses the lateral diffusion of photocarriers by enhancing recombination. A device simulation verified that a higher spatial resolution could be obtained by adjusting the gap between the modulated and constant light. It was also found that a higher intensity and a longer wavelength of constant light was more effective. However, there exists a tradeoff between the spatial resolution and the amplitude of the photocurrent, and thus, the signal-to-noise ratio. A tilted incidence of constant light was applied, which could achieve even higher resolution with a smaller loss of photocurrent. KW - Light-addressable Potentiometric Sensor KW - novel photoexcitation method KW - tilted constant illumination KW - spatial resolution Y1 - 2014 U6 - http://dx.doi.org/10.1016/j.proeng.2014.11.369 SN - 1877-7058 N1 - EUROSENSORS 2014 ; European Conference on Solid-State Transducers <28, 2014> VL - 87 SP - 456 EP - 459 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Miyamoto, Ko-ichiro A1 - Yoshida, Midori A1 - Sakai, Taito A1 - Matsuzaka, Atsushi A1 - Wagner, Torsten A1 - Kanoh, Sanoh A1 - Yoshinobu, Tatsuo A1 - Schöning, Michael Josef T1 - Differential setup of light-addressable potentiometric sensor with an enzyme reactor in a flow channel JF - Japanese Journal of Applied Physics. 50 (2011) Y1 - 2011 SN - 0021-4922 SP - 04DL08-1 EP - 04DL08-5 PB - Japan Society of Applied Physics CY - Bristol ER -