Refine
Year of publication
- 2024 (29)
- 2023 (33)
- 2022 (47)
- 2021 (46)
- 2020 (59)
- 2019 (70)
- 2018 (67)
- 2017 (66)
- 2016 (51)
- 2015 (68)
- 2014 (59)
- 2013 (63)
- 2012 (70)
- 2011 (74)
- 2010 (69)
- 2009 (78)
- 2008 (57)
- 2007 (52)
- 2006 (46)
- 2005 (43)
- 2004 (76)
- 2003 (46)
- 2002 (53)
- 2001 (50)
- 2000 (61)
- 1999 (38)
- 1998 (37)
- 1997 (32)
- 1996 (32)
- 1995 (19)
- 1994 (13)
- 1993 (19)
- 1992 (13)
- 1991 (12)
- 1990 (17)
- 1989 (20)
- 1988 (21)
- 1987 (26)
- 1986 (7)
- 1985 (9)
- 1984 (9)
- 1983 (6)
- 1982 (24)
- 1981 (16)
- 1980 (30)
- 1979 (20)
- 1978 (27)
- 1977 (13)
- 1976 (16)
- 1975 (14)
- 1974 (4)
- 1973 (3)
- 1972 (6)
- 1971 (1)
- 1969 (1)
- 1968 (2)
- 1967 (1)
Institute
- Fachbereich Medizintechnik und Technomathematik (1941) (remove)
Has Fulltext
- no (1941) (remove)
Document Type
- Article (1537)
- Conference Proceeding (162)
- Book (98)
- Part of a Book (63)
- Doctoral Thesis (28)
- Patent (17)
- Report (13)
- Other (8)
- Conference: Meeting Abstract (5)
- Habilitation (4)
Keywords
- Natural language processing (5)
- LAPS (4)
- CellDrum (3)
- Field-effect sensor (3)
- Light-addressable potentiometric sensor (3)
- Paired sample (3)
- hydrogen peroxide (3)
- impedance spectroscopy (3)
- Bacillus atrophaeus (2)
- Biocomposites (2)
To study chemical and biological processes, spatially resolved determination of the concentrations of one or more analyte species is of distinct interest. With a light-addressable potentiometric sensor (LAPS), chemical images can be created, which visualize the concentration distribution above the sensor plate. One important challenge is to achieve a good lateral resolution in order to detect events that take place in a small and limited region. LAPS utilizes a focused light spot to address the measurement region. By moving this light spot along the semiconductor sensor plate, the concentration distribution can be observed. In this study, we show that utilizing a pulse as light excitation instead of a traditionally used continuously modulated light excitation, the lateral resolution can be improved by a factor of 6 or more.
A light-addressable potentiometric sensor (LAPS) can measure the concentration of one or several analytes at the sensor surface simultaneously in a spatially resolved manner. A modulated light pointer stimulates the semiconductor structure at the area of interest and a responding photocurrent can be read out. By simultaneous stimulation of several areas with light pointers of different modulation frequencies, the read out can be performed at the same time. With the new proposed controller electronic based on a field-programmable gate array (FPGA), it is possible to control the modulation frequencies, phase shifts, and light brightness of multiple light pointers independently and simultaneously. Thus, it is possible to investigate the frequency response of the sensor, and to examine the analyte concentration by the determination of the surface potential with the help of current/voltage curves and phase/voltage curves. Additionally, the ability to individually change the light intensities of each light pointer is used to perform signal correction.
Ein lichtadressierbarer potentiometrischer Sensor (LAPS) kann die Konzentration eines oder mehrerer Analyten ortsaufgelöst auf der Sensoroberfläche nachweisen. Dazu wird mit einer modulierten Lichtquelle die Halbleiterstruktur des zu untersuchenden Bereiches angeregt und ein entsprechender Photostrom ausgelesen. Durch gleichzeitige Anregung mehrere Bereiche durch Lichtquellen mit unterschiedlichen Modulationsfrequenzen können diese auch zeitgleich ausgelesen werden. Mit der neuen, hier vorgestellten Ansteuerungselektronik integriert in einem "Field Programmable Gate Array" (FPGA) ist es möglich, mehrere Leuchtquellen gleichzeitig mit unterschiedlichen, während der Laufzeit festlegbaren Frequenzen, Phasen und Lichtintensitäten zu betreiben. Somit kann das Frequenzverhalten des Sensors untersucht und die Konzentration des Analyten über das Oberflächenpotential mit Hilfe von Strom/Spannungs-Kurven und Phase/Spannungs-Kurven bestimmt werden.
Semiconductor-based chemical imaging sensors, like the light-addressable potentiometric sensor (LAPS) or the pH-imaging sensor based on a charge-coupled device (CCD), are becoming a powerful tool for label-free imaging of biological phenomena. We have proposed a polyion-based enzymatic membrane to develop an acetylcholine (ACh) imaging sensor for neural cell-activity observations. In this study, a CCD-type ACh-imaging sensor and a LAPS-type ACh-imaging sensor were fabricated and the prospect of both sensors was clarified by making a comparison of their basic characteristics.
Light-addressable potentiometric sensors (LAPS) are field-effect-based sensors. A modulated light source is used to define the particular measurement spot to perform spatially resolved measurements of chemical species and to generate chemical images. In this work, an organic-LED (OLED) display has been chosen as a light source. This allows high measurement resolution and miniaturisation of the system. A new developed driving method for the OLED display optimised for LAPS-based measurements is demonstrated. The new method enables to define modulation frequencies between 1 kHz and 16 kHz and hence, reduces the measurement time of a chemical image by a factor of 40 compared to the traditional addressing of an OLED display.
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.