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Detection of triacetone triperoxide using temperature cycled metal-oxide semiconductor gas sensors
(2015)
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.
The development of new interfaces for (bio-)chemical sensors requires comprehensive analyses and testing. The light-addressable potentiometric sensor (LAPS) can be used as a platform to investigate the sensitivity of a newly developed interface towards (bio-)chemical agents. LAPS measurements are spatially resolved by utilisation of focused light beams to define individual measurement spots. In this work, a new digitally modulated LAPS set-up based on an FPGA design will be introduced to increase the number of measurement spots, to shorten the measurement time and to improve the measurement accuracy.
The light-addressable potentiometric sensor (LAPS) has the unique feature to address different regions of a sensor surface without the need of complex structures. Measurements at different locations on the sensor surface can be performed in a common analyte solution, which distinctly simplifies the fluidic set-up. However, the measurement in a single analyte chamber prevents the application of different drugs or different concentrations of a drug to each measurement spot at the same time as in the case of multi-reservoir-based set-ups. In this work, the authors designed a LAPS-based set-up for cell culture screening that utilises magnetic beads loaded with the endotoxin (lipopolysaccharides, LPS), to generate a spatially distributed gradient of analyte concentration. Different external magnetic fields can be adjusted to move the magnetic beads loaded with a specific drug within the measurement cell. By recording the metabolic activities of a cell layer cultured on top of the LAPS surface, this work shows the possibility to apply different concentrations of a sample along the LAPS measurement spots within a common analyte solution.
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.