抄録
Micropump using boiling propagation as the actuation mechanism is proposed. A film heater on a silicon (Si) substrate placed facing a microchannel is powered pulsewise. Boiling propagation is triggered at a high wall superheat by generating a vapor bubble at the end of the heater. The repetition of unidirectional propagation over the heater length produces continuous pumping action in the microchannel. The propagation configuration, propagation velocity, propagating bubble size, maximum allowable repetition frequency and the wall superheat range for the occurrence of propagation are investigated under pool boiling conditions using ink for a thermal inkjet printer. The results obtained for Si substrate are compared with those on a quartz glass (SiO2). No significant difference in the propagation behaviors and the pumping head is observed between the Si and SiO2 substrates for a given pulse period, wall superheat and repetition frequency. However, a larger pulse power is required for the Si substrate because of its higher heat diffusion property. The resulting larger heat storage in the substrate before the boiling onset causes the delay of bubble collapse after the pulse heating. The gradual increase in the temperature of the thin Si substrate during the repetition of the pulse heating results in a lower allowable repetition frequency and therefore in lower pumping performance compared with those for the SiO2 substrate.
