A simple method to fabricate electrochemical sensor systems with predictable high-redox cycling amplification

In this paper an easy to fabricate SU8/glass-based microfluidic sensor is described with two closely spaced parallel electrodes for highly selective measurements using the redox cycling effect. By varying the length of the microfluidic entrance channel, a diffusion barrier is created for non-cycling species effectively increasing selectivity for redox cycling species. Using this sensor, a redox cycling amplification of ∼6500× is measured using the ferrocyanide redox couple. Moreover, a simple, but accurate analytical expression is derived that predicts the amplification factor based on the sensor geometry.