A gas-flow device consisting of a valveless micro jet pump and flow sensor has been designed and fabricated using a
Si micromachining process. The valveless micro pump is composed of a piezoelectric lead zirconate titanate (PZT)
diaphragm actuator and flow channels. The design of the valvless pump focuses on a crosss junction formed by the neck
of the pump chamber and one outlet and two opposite inlet channnels. The structure allows differences in the fluidic
resistance and fluidic momentum inside the channels during each pump vibration cycle, which leads to the gas flow
being rectified without valves. Before the Si micro-pump was developed, a prototype of it was fabricated using
polymethyl methacrylate (PMMA) and a conventional machining techinique, and experiments on it confirmed the
working principles underlying the pump. The Si micro-pump was designed and fabricated based on these working
principles. The Si pump was composed of a Si flow channel plate and top and botom covers of PMMA. The flow
channels were easily fabricated by using a silicon etching process. To investigate the effects of the step nozzle structure
on the gas flow rate, two types of pumps with different channel depths (2D- and 3D-nozzle structures) were designed,
and flow simulations were done using ANSYS-Fluent software. The simulations and excperimental data revealed that the
3D-nozzle structure is more advantageous than the 2D-nozzle structure. A flow rate of 4.3 ml/min was obtained for the
pump with 3D-nozzle structure when the pump was driven at a resonant frequency of 7.9 kHz by a sinusoidal voltage of
40Vpp. A hot wire was fabricated as a gas-flow sensor near the outlet port on the Si wafer.
This paper reports on the design and simulation of a new valve-less pump for use in microfluidic applications. The
simple-structure micropump comprises a piezoelectric Pb(Zr,Ti)O<sub>3</sub> (PZT) - Si diaphragm and flow channels which are
fabricated using silicon micromachining techniques. The silicon diaphragm (5×5×0.05mm<sup>3</sup>) is driven by the PZT (45-μm
thick) actuator that has quick response time and large driving force with low power consumption. A key technology to
realize the pump diaphragm is the PZT-Si bonding process using a thin gold film as an intermediate layer. Under
fabrication conditions of 550°C and 0.8 MPa, the strength of the bonding was experimentally validated to be 13 MPa.
The maximum displacement of the diaphragm was measured to be 3 μm<sub>0-P</sub> with driving voltage of 30 V<sub>p-p</sub> at resonance
frequency of 10 kHz. Structural analysis of the diaphragm was done in terms of three-dimensional model using
commercial software ANSYS. The flow channels are easily fabricated by silicon etching process. Design of flow
channels focused on a cross junction formed by neck of the pump chamber, one outlet and two opposite inlet channels.
This structure allows a difference in fluidic resistance and fluidic momentum to be created inside the channels during
each pump vibration cycle. Two designs of the devices which have different channel depths, namely type A and type B,
was investigated. Flow simulation was done by numerical transient model (using ANSYS-Fluent), in which only the
measured deformation of the PZT diagram is applied and therefore no other assumptions are required. The results
showed that the mass flow rate of the type A is 0.129×10<sup>-6</sup> kg/s (mean flow rate of 6.3 ml/min) and that of type B is
1.65×10<sup>-6</sup> kg/s (mean flow rate of 80.8 ml/min).