Integrated micro fluidic system using electrochemically generated bubbles
We developed a micro fluidic system by integrating on-chip micro pumps and check valves that function by means of a hydrogen bubble that is generated or extinguished electrochemically (Fig.1). Essential elements were thin-film three-electrode systems, including a platinum black working electrode. Micro flow channels and containers for electrolyte solutions were formed on a polydimethylsilixane (PDMS) substrate. The growth and shrinkage of the bubble were controlled reproducibly by setting the working electrode potential at a constant value. The elastic nature of the bubble clogged in a valve compartment in the middle of the flow channel hindered the effective passage of the solution. By making the valves open and close cooperatively, a solution could be introduced into the system and transported in the flow channel (Fig.2). When two dye solutions were transported and merged in a flow channel, sheath flows were observed, reflecting a low Reynold’s number. As a model system, two solutions containing luciferin and luciferase were introduced separately, transported, and mixed. Chemiluminescence originating from the enzymatic reaction was observed.
Fig. 1 Structure of the electrochemical liquid transport system with integrated on-chip micro pumps and valves. (a): construction of the system. (b): completed system showing the mutual relation between the respective components.
Fig. 2 Introduction of an Orange G solution from the injection port on the right. The solution entered from the injection port in (a) and moved to the syringe of the pump in (b).