Electronics Weekly
The 3.4 x 3.6mm chips were designed on Cadence Virtuoso and fabricated at Austria microsystems on a 350nm triple-well process. On these, the active area is a 16 × 16 array sensors covering 1.6 x 1.6mm in total. Each pixel includes a photo diode, working with LEDs mounted elsewhere.
The chips were bonded onto a large ceramic package, onto which a circular reservoir around 20mm across was formed to hold fluids, centred on the chip.
Two thin intersecting vertical epoxy walls divide the reservoir into four equal segments, each with a quarter of the pixels in one corner. Construction of these walls was a complex multi-stage polymer micro-fabrication process, needed to achieve the necessary precision. On average, 36 functioning pixels were available per segment after wall construction, according to supplementary information associated with the paper ‘An integrated portable system for single chip simultaneous measurement of multiple disease associated metabolites’ in the journal Biosensors and Bioelectronics, which describes this work.
To invoke an colour change that an be detected by the pixels, specific enzymes are used.
To detect the body chemicals cholesterol and glucose, ‘peroxidase coupled colour reactions’ were used, known as COD and GOD respectively. CHOD, XOD and SOX are also available to measure the concentrations of choline, xanthine and sarcosine if required.
Samples of blood, urine or a reference solution containing cholesterol or glucose were tested in the sensor, and within two minutes produced results.
“There was no statistically significant difference between the two groups of measurements as indicated by the p values (> 0.05 using Student unpaired t-test),” according to the paper. “These results indicate that our CMOS-based device can reliably quantify these metabolites in clinical samples. In addition, this technology offers the advantage of performing multiplexed detection of different analytes covering metabolic and immunological biomarkers.”
“We have been able to detect and measure multiple metabolites associated with myocardial infarction, or heart attack, and prostate cancer simultaneously using this device. This device has potential to track progression of the disease in its early phase and is ideally suited for the subsequent prognosis”, said Glasgow engineer Dr Samadhan Patil.
The intention is for the sensing chip and its associated plastic components to be disposeable, in a non-disposeable reader that included LEDs and electronics to allow the sensor to be controlled, and its output viewed, via an Android tablet.
Glasgow’s engineering school worked with its school of life sciences on the project, with funding from the Engineering and Physical Sciences Research Council (EPSRC).
