A CMOS-based integrated-system architecture for a static cantilever array

A monolithic, integrated sensor system architecture is presented that features microcantilevers operated in the deflection mode as transducer elements for detecting (bio)chemical compounds. The cantilevers have been coated with polymer layers to detect volatile organic compounds, such as ethanol. The analyte-sorption-induced surface-stress changes of the cantilevers have been detected by piezoresistive Wheatstone bridge configurations embedded in the cantilevers. The integrated readout circuitry includes a chopper-stabilized amplifier, which performs a low-noise, low-offset amplification of the μV-range sensor signal. Additional low-pass filtering and a programmable offset compensation stage on the chip provide a good signal-to-noise ratio. A sigma–delta analog-to-digital converter (ΣΔ-ADC) delivers the measured data to the outside world via a digital serial interface. The monolithic integration reduces the sensitivity to external interference and enables autonomous device operation. The focus of the paper is on the system design and integration, which can also be applied to other types of cantilevers or cantilevers featuring different geometries.