Active on-chip microfluidic transport system based on electrochemical bubble formation and its application to bio/chemical sensing

An integrated microfluidic transport system was constructed based on electrochemical bubble formation. The basic structure of the pumps and valves consisted of three-electrode systems to produce or shrink hydrogen bubbles and a polydimethylsiloxane (PDMS) diaphragm to separate the electrolyte solution from a sample solution in a micro flow channel. The production and extinction of the bubbles caused deformation of the PDMS diaphragm and the solution in the flow channel was mobilized. Two different solutions could be introduced from two injection ports, transported through the flow channels, and mixed in a mixing channel. By stopping the flows, the solutions mixed rapidly by diffusion. To demonstrate its applicability to micro analysis systems, fluorometric sensing of hydrogen peroxide was conducted. An enzyme solution and a solution containing enzyme substrates were injected from two injection ports, mixed, and allowed to react in the mixing channel. Distinct fluorescence was observed, and a linear relationship was observed between the fluorescence intensity and the concentration of hydrogen peroxide. The sensing scheme was also applied to the detection of L-glutamate.