Microfluidic based differential electrochemical sensors
Lab-on-a-chip systems aim to integrate analytical techniques on a single chip to achieve high-throughput measurements with little reagent. Microfluidic devices use the advantage of fluid dynamics in microscale to generate new physical phenomena which are less familiar in macroscale. Laminar flow is one of these emergent phenomena in microscale dimensions. Fluids flowing in a microchannel with low Reynolds number (Re), have small inertial effects which suppress the turbulent mixing. Ability to control liquids without turbulent mixing provides new tools for integration of analytical techniques on a single chip. In this work we present a new type of electrochemical device based on hydrodynamic modulation in a microfluidic channel. The presented microfluidic device is a kind of hydrodynamic modulation voltammetry (µ-HMV) that uses a periodic modulation of two laminar streams of buffer and analyte solutions in a micro channel. The periodic modulation of the laminar flow generates periodic variation of mass transport to the electrode surface. The generated periodic electrochemical current is detected by a phase-sensitive detector. The differential electrochemical sensor eliminates charging and other transient background current and provides high sensitivity with a detection limit of 10 nM. This technique provides a convenient hydrodynamic electrochemical detection with a relatively simple and compact instrument which does not require any moving mechanical parts.