We demonstrate a peristaltic micropump that utilizes traveling waves on polymer membranes to transport liquids. This micropump requires no valves and, more importantly, the traveling waves can be generated by a single actuator. These features enable the design of simple, compact devices. This micropump has a hydraulic displacement amplification mechanism (HDAM) that encapsulates an incompressible fluid with flexible polymer membranes made of polydimethyl siloxane. A microchannel is attached to the top side of the HDAM. We used a cantilever-type piezoelectric actuator to oscillate the flexible membrane at the bottom of the HDAM, while the top-side membrane drives the liquid in the channel. This format enables rectangular parallelepiped micropumps as compact as 36 mm long, 10 mm wide and several millimeters high, depending on the channel height. Experiments using the fabricated micropumps equipped with microchannels of various heights revealed that the flow rate was dependent on the ratio of the amplitude of the traveling waves to the height of the fluidic channel. The manufactured micropump could successfully generate a maximum flow rate of 1.5 ml min−1 at 180 mW.
We studied superfluidity of liquid 4 He confined in an array of well-characterized straight nanopores of porous alumina (PA). The PA plate sample of 45 nm pore size is set in an annular flow channel and the superflow is detected by torsional oscillator (TO) technique. Superfluid transition Tc in the nanopores is suppressed by 3.5 mK from the bulk λ point. Tc is consistent with the temperature at which the healing length is equal to the pore radius. We have observed many anti-crossing anomalies in the TO frequency associated with dissipation peaks, which are attributed to the coupling to second sound resonances.
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