CMOS-based colour-change pH measurement system

Abstract

A real-time pH detection and monitoring sensor system using a novel design neuromorphic CMOS optical sensor chip is presented. The system uses Bogen's universal indicator solution combined with a white light source and the CMOS optical sensor chip to measure pH as a function of colour change in a sample. Bogen's universal indicator solution causes a colour change in a sample according to the pH of the sample. The output voltage from the colour-sensitive CMOS photodetector circuit on the chip is proportional to the pH of the sample. Experimental results show that this sensor system can determine the pH of a sample from pH 1 to 9 in real-time. The sensor chip is implemented in AMI 1.5 mm CMOS technology available through MOSIS.

A 3-Bit Pseudo Flash ADC Based Low-Power CMOS Interface Circuit Design for Optical Sensor

“…A white light generated from a light source will be coded by the color of the solution as it passes through it, and the light wavelength will be processed by the light sensor microsystem to determine the pH level. Similar methods have been used previously [8].…”

“…Low cost and low power sensing is becoming a very important feature in emerging microsystems applications particularly in the area of biomedical and minimally invasive medical devices. Optical sensors are used in (bio) chemical [1][2][3], monitoring biological events [4][5][6] and environmental sensing applications such as level measurement for pH O 2 , CO2, and determination of molecular concentration [7][8][9]. Optical sensors are of primary interest to the research community due to their intrinsic advantages such as suitability for in-line measurement, low cost and long term usage.…”

A low power interface circuit design for a CMOS based smart optical sensor

“…The interface circuit has been previously tested with discrete components as a proof of concept and successful results has been obtained [7]. The main blocks of the proposed interface circuit are discussed briefly below.…”

“…CMOS sensors based on field effect transistors, Ion sensitive field effect transistor (ISFET), are available as integrated circuit however, they still require reference electrode [5,6] limiting their practical application; needs post deposition processing while fabrication [7] increasing their cost.…”

Design and characterization of multi-color sensor circuit

“…Color sensors are also valuable for biochemical applications such as pH sensor as part of environmental monitoring device [1], concentration analysis of uric acid in urea [2], and to monitor biological events with integration to fluorescent probes [3,4]. The objective of this research is to validate a novel four color sensor architecture using simulation and experiment as a proof of concept for a future implementation as an integrated circuit using the Austria Microsystems CMOS 350 nm technology [5].…”