Cantilever-based chemical sensors for detecting catalytically produced reactions and motility forces generated via electrokinetic phenomena

This paper reports the fabrication, characterization, and modeling of a chemical sensor constructed from a microfabricated silicon cantilever, coated with gold, which is modified using photolithography techniques to contain a silver feature on the free-standing edge. When immersed in a fuel solution such as hydrogen peroxide, catalytic reactions occurring at the bimetallic silver-gold junction cause a catalytic force to act on the cantilever. The catalytic reaction is detected by measuring change in resonance frequency of the cantilever using a position-sensitive split photodiode and atomic force microscopy instrument. A model based on the Cleveland method is developed to quantify the forces produced and to study the effect of change of hydrogen peroxide concentration on the magnitude of the force. The force is observed to increase linearly for lower concentrations of hydrogen peroxide and level off at higher concentrations. The chemical sensor offers a possible method for using catalytically produced forces in microelectromechanical systems and microfluidic devices.