A Microfabricated Pistonless Syringe Pump Driven by Electro‐Conjugate Fluid with Leakless On/Off Microvalves

In contrast to microfluidic devices, bulky syringe pumps are widely used to deliver a small amount of solution with high accuracy. Miniaturizing the syringe pump is difficult due to the scale effect in the microscale where the friction of the piston-cylinder is dominant and there are few high-power microactuators. To solve these problems, an on-chip microsyringe pump without mechanical sliding parts and with high power sources is proposed. The microsyringe pump utilizes the interface between water and oil (electro-conjugate fluid, ECF) instead of a piston and an electrohydrodynamic (EHD) flow driven by ECF in place of a linear actuator. ECF as a functional fluid has two capabilities: a) making the water-oil interface in microchannels and b) generating an active ECF flow at an applied voltage to withdraw and infuse aqueous solution by the interface. To control the flow direction, ECF-driven leakless on/off microvalves are also integrated. It is demonstrated that the proposed ECF microsyringe pump synchronized with the ECF on/off microvalves can control the withdrawing and infusing of aqueous solution with high resolution and precision. The experiments prove the feasibility of the microsyringe pump to be embedded as a module for the precise and linear control of flow rates in microfluidic devices.