Sensor Fabrication and On-Chip Impedance Spectroscopy for Milk Adulteration Detection

Milk adulteration has become a major problem in Indian subcontinent with commercially avail-\ud able milk being adulterated with variety of adulterants, which may cause hazardous and irreversible\ud health damage to the consumers. The current trend to detect the adulterants in the milk are adul-\ud terant specific, or require a high end laboratory equipment. This work focuses on developing a hand\ud held low power platform to detect adulterants in the milk so that pure milk and contaminated milk\ud can be distinguished on-site, rather than focusing on the particular adulterant. Here conductivity\ud of milk as inherent physical property of milk is studied, and chosen as a marker to differ pure milk\ud from adulterated one. Experiments are performed to study the effects of various adulterants on milk\ud conductivity. An on-chip impedance sensor with glass substrate and gold electrode is fabricated to\ud further lab-on-chip platform. Based on the conducted study an on-chip impedance read-out circuit is\ud designed to with concluded specifications, so that low-power handheld platform can be implemented.\ud An on-chip circuit for impedance spectroscopy circuit is realized using a UMC-180nm technology.\ud This low power, on-chip impedance spectroscopy based system for milk adulteration detection con-\ud sists of an instrumentation amplifier(IA) with rail-to-rail ICMR, a high resolution comparator, Gm\ud cancellation based integrator, peak detector and a low pass Biquad filter. A novel OTA structure\ud with high gain and low bandwidth is used. The power consumption of each block is kept minimum\ud keeping into mind the application of the full system for portable battery powered operation