An instrumentation design for microsignal output from piezoresistive microcantilever biosensor for human stress

This paper concerns the development of a potentiometric instrumentation circuit for integration with a PZR microcantilever biosensor to detect human stress. It embodies the design of transduction, filtering, stabilization and linearization of micro-signals from a biosensor. The sensing principle is based on immobilization of the bio-receptor to produce a biochemical reaction. The novel biosensor integrated with the potentiometric instrumentation converts this biochemical event into a measurable electrical signal. Input is the level of salivary alpha amylase activity corresponds to human stress level. The first phase transduces the changes in enzymatic reaction into resistivity. The subsequent stages condition the signal to attain an output of 0-5V from a potentiometric input of 108.6 to -100mV, equivalent to sensor resistivity range of 1.2-1.3KΩ. The design for filtering phase employs a first order high and low pass filter to capture stress signals, known with frequency between 0.15-0.4Hz. 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 transduction, filtering and linearization phase respectively.