Silicon microresonator arrays: A comprehensive study on fabrication techniques and pH-controlled stress-induced variations in cantilever stiffness

We introduce a detailed design and fabrication process of Silicon microcantilever arrays for biomolecular detection in liquid environment, utilized with laser readout. We present typical fabrication problems and provide related solutions to obtain high quality resonators via a robust, reproducible and high-yield process. Sensors in these arrays are individually functionalized with self-assembled chemical monolayers exposing various pH-active end-groups into solution. Dynamic-mode controlled frequency measurements in varying pH solutions result in stress-induced change of the sensor spring constant. pH changes in the solution lead to deprotonation of exposed functional chemical groups at high pH and the repulsive charges induced strain is proportional to the quantity and confinement of charges at the sensor interface. These built-up strains that affect the mechanical stiffness can be reversibly relaxed when exposed again to low pH environments.