This article reports a new micropump developed by NIKKISO. The micropump is a piezo-actuated diaphragm pump in a low flow rate range of L/min. The advantage is to be very compact in size compared to conventional pumps such as syringe pump and plunger pump using electromagnetic motors. Moreover, the piezoelectric actuator is quite low power consumption, so the pump can be battery-operated. Therefore the micropump is well suited not only for downsizing of existing devices but also for new application like portable devices.

This pump consists of a pump chamber with a diaphragm (pumping membrane) and two passive check valves. The diaphragm actuated by piezoelectric disc glued onto it generates a stroke volume and causes pressure for suction and discharge flow alternately. This is the same pumping principle as the heart. The pumping of liquid is shown in video 1 below. These structures are manufactured using Micro Electro Mechanical System (MEMS) technology, a series of photolithography and etching processes similar to traditional semiconductor processes.

Photograph and specifications of the pump are shown as follows. A MEMS-manufactured glass chip is set in a ceramic package. Two tubes in near side are fluidic inlet and outlet, and two pins in far side are electrical connection. This model is just an example and we can design for user's demand specification (flow rate, pressure, etc).

Fluid

The micropump has high chemical resistance because it is made of glass and single crystal silicon. It can handle various chemicals including organic solvents and acid solutions except for some alkaline solutions. However it may not be able to pump high viscosity liquids or liquids containing particles.

For Both Liquid and Gas

The micropump has the ability to pump gas as well as liquid. In order to pump gas, pump design should be taken into account that gas is compressible fluid. The ability was archived by maximizing the compression ratio, which is a ratio between stroke volume and dead volume. Consequently it makes the pump self-priming and bubble tolerant. In addition, it also enable the pump to push out liquid in a vial by air pressure (see video 2), and reversely suck liquid sample like pipette or dropper.

Pulseless pump available

Reciprocating pump including this micropump generate a pulsatile flow in principle when used by itself. We provide a pulseless pump in case that an application is adversely affected by the pulsatile flow. The pulseless pump consists of two micropumps connected in parallel. By running them in counter strokes, the discharge flow will become a continuous flow without pulses (video 3).

Nikkiso is developing some micro fluidic devices using MEMS technology. These devices are considered to be necessary in the field of miniaturized chemical analysis called "Micro total analysis system(TAS)" and rapid diagnostic testing near patient called "Point of care testing (POCT)" and so on.

(November 9, 2005)