Micropumps are important components of advanced microfluidic systems. Here, polyimide (PI) as an advantageous structural material for flexible micropumps was focused on. This is because PI has many advantageous properties such as high thermal stability and superior mechanical strength. However, the difficulty in realizing an all-PI micropump lies in fabricating microstructures on PI film surfaces. In this paper, we present a novel all-PI micropump fabricated using hot embossing. The micropump had diffuser/nozzle valves and functioned by vibrating a 2-µm-thick PI diaphragm with alternating air pressures between 0 and 10 kPa at a frequency of 3 Hz. The height and diameter of the PI micropump chamber were 200 µm and 5 mm, respectively. The flow rate of water in the micropump was 34 µl/min. This micropump is suitable for flexible microfluidic systems.

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A miniaturized diffuser/nozzle micropump with extremely thin (only 2.1 µm in thickness) polyimide (PI) membranes was fabricated on a 60-µm-thick Si wafer using simple photolithography processes. The diameter of the diaphragm was 2 mm, and the chamber depth was 60 µm. The micropump was functioned by deforming the membranes with alternating air pressure. The ethanol flow rate of the micropump was over 400 nl/min at 2.5 Hz with an actuated pressure of 5 kPa. The measured flow rate was relatively higher than those of previously reported micropumps with a similar chamber volume owing to the large deflection (over 40 µm) of the PI membrane. The micropump processing issues of plasma induced damage to the PI membrane during Si chamber etching and the behaviors of the static and dynamic deflections of the PI membrane was also discussed. On the basis of the advantages of photolithography processes and the good performance of the micropump, it is expected that the micropump can be fabricated on silicon integrated circuit chips.

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