  Silicon nanowires have been surface functionalized with the enzyme urease for
biosensor applications to detect and quantify urea concentration. The device is
nanofabricated from a silicon on insulator (SOI) wafer with a top down
lithography approach. The differential conductance of silicon nanowires can be
tuned for optimum performance using the source drain bias voltage, and is
sensitive to urea at low concentration. The experimental results show a linear
relationship between surface potential change and urea concentration in the
range of 0.1 to 0.68 mM. The sensitivity of our devices shows high
reproducibility with time and different measurement conditions. The nanowire
urea biosensor offers the possibility of high quality, reusable enzyme sensor
array integration with silicon based circuits.
