A Simple and Convenient Set-Up of Light Addressable Potentiometric Sensors (LAPS) for Chemical Imaging Using a Commercially Available Projector as a Light Source

摘要

Light addressable potentiometric sensors (LAPS) are important semiconductor based label free sensingtools that are useful for visualizing the 2-D distribution of chemical species because of their lightaddressing capability at measurement sites. However, the expense and complexity of the LAPS lightmodulation set-up is highly inconvenient. To address this issue, we demonstrate a simple andconvenient LAPS set-up that uses a commercially available projector as a programmable scanninglight source. In the proposed set-up, an illuminated light spot used to excite electron-hole pairs insilicon was generated from a projector and an objective lens with the aid of commercially availablecomputer software. Using a projector is an easy and flexible method of controlling the shape, size,movement, and the modulation frequency of the measurement spot in a user defined manner through acomputer software interface. This approach avoids the complexity associated with using an X-Y stageor multiple light sources for scanning the LAPS surface. In addition, it reduces the setup time for theoptical system and language programming for the control of digital micro-mirror device by usingARM-based processor. Using the set-up developed here, a minimum measurement spot of size 22x222 was achieved. Additionally, the photoresponse-voltage characteristics, constant bias measurementand the pH sensitivity were successfully studied with this set-up. Finally, the pH imaging ability of thissetup was successfully demonstrated.