Highly Sensitive ?R/R Measurement System for Nano-electro-Mechanical Cantilever Based Bio-sensors

Functionalized piezoresistive nano-electromechanical cantilevers are promising tools for sensor applications. This paper reports an integration of custom fabricated piezoresistive cantilever sensors and sensitive analog front end circuit for detection of bio-markers. The system operates on the principles of nano-meter deflection of cantilever sensors, due to antigen-antibody interactions, which in turn exhibits change in piezoresistance. The instrumentation hardware can measure resistance changes down to 14 parts per million (ppm) and maximum sensitivity is 2.134 V/ppm. Experiments have been performed with 90KΩ and 1MΩ base resistances. A wheat stone bridge connected resistors has been used where the functionalized cantilever forms one of the arms. The measured results using this battery operated system has been presented along with calibration technique. The size of this LCD (Liquid crystal display) based system was reduced to fit into a hand held point-of-care form factor. In addition, users can operate this measurement system with the help of computer to connect to the Internet. Measurement results are presented with the introduction of bovine serum albumin (BSA) over the cantilever sensors. This demonstrates the possible application for detection of myocardial infarction in clinical settings.