Development of micro-vibrating flow pumps using MEMS technologies

In the present paper, we propose a micro-vibrating flow pump (micro-VFP), which is a novel micropump. The micro-VFP is constructed using an actively vibrating valve that has a cantilever-like structure fixed on a wall of a microchannel and a slit orifice downstream. The slit orifice is designed to make the flow asymmetric around the vibrating valve and to effectively generate a net flow in one direction. At the same time, the valve works as an actuator to induce liquid flow in the microchannel. Since the valve is made of a flexible material including magnetic particles, it is manipulated by changing the magnetic field from outside the micro-VFP. This design allows external operation of the micro-VFP without any electrical or mechanical connections. In addition, the micro-VFP, which realizes pumping with a chamber free design, is advantageous for implementation in a small space. In order to demonstrate its basic pumping performance, a prototype micro-VFP was fabricated in a microchannel with a cross section of 240 mu m x 500 mu m using microelectromechanical systems technologies. The vibration characteristics of the valve were investigated using a high-speed camera. The pump performance at various actuation frequencies in the range of 5 to 25 Hz was evaluated by measuring the hydrostatic head and the flow rate. The proposed micro-VFP design exhibited an increase in performance with the driving frequency and had a maximum shut-off pressure of 3.8 +/- 0.4 Pa and a maximum flow rate of 0.38 +/- 0.02 mu l/min at 25 Hz. Furthermore, in order to clarify the detailed pumping process, the flow characteristics around the vibrating valve were investigated by analyzing the velocity field based on micron-resolution particle image velocimetry (micro-PIV). The validity of the hydrostatic measurement was confirmed by comparing the volume flow rate with that estimated from micro-PIV data. The present study revealed the basic performance of the developed micro-VFP.