We are developing a method for high-throughput screening using arrays of `nanowells' built into a silicon substrate. These wells can serve as bioreactors for studying a variety of biochemical reactions such as the enzymatic activity that occurs in yeast metabolism. For a variety of studies it is important to know the volume of liquid that has been deposited in a given well and/or to monitor the evaporation of the liquid. Using silicon as our substrate means that we can take advantage of the ability to build microelectronics into the wells in order to develop `smart' wells.