Development of a potentiometric circuit for A PZR microcantilever biosensor for measurement of human stress

This paper describes design and development of transduction, filtering, stabilisation and linearization stages of a potentiometric circuit to convert micro-signals from a PZR microcantilever biosensor into readable signals for human stress. The biosensing principle is based on immobilization of the bioreceptor to produce a biochemical reaction. The novel potentiometric circuit converts this biochemical event into a measurable electrical output. The transduction stage transforms the changes in enzymatic reaction in salivary alpha amylase, influenced by the level of human stress into resistivity within range of 1.2-1.3 kΩ and corresponding potential of 108.6 to -100 mV. The subsequent stages condition the signal to attain an output of 0-5 V. The design for filtering stage employs a first order high and low pass filter to capture stress signals, known with frequency of 0.15-0.4 Hz. Performance of the circuit is evaluated with simulation and experimental study. On the average, discrepancy less than 3.69%, 4.5% and 3.7% is found between simulation and experimental results for the three stages of the circuit respectively.