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Filter-based sampling techniques are the conventional way to collect particulate matter, but particles collected and entangled in the filter fibers are difficult to be removed and thus not suited for the following cell- and animal-based exposure experiments. Collecting aerosol particles in powder form using a cyclone instead of a filter would be a possible way to solve this problem. We developed a hybrid virtual-impactor/cyclone high-volume fine and coarse particle sampler and assessed its performance. The developed system achieved 50% collection efficiency with components having the following aerodynamic cut-off diameters: virtual impactor, 2.4 μm; fine-particle cyclone, 0.18-0.30 μm; and coarse-particle cyclone, 0.7 μm. The virtual impactor used in our set-up had good PM2.5 separation performance, comparable to that reported for a conventional real impactor. The newly developed sampler can collect fine and coarse particles simultaneously, in combination with exposure testing with collected fine- and coarse- particulate matter samples, should help researchers to elucidate the mechanism by which airborne particles result in adverse health effect in detail.

Volume displacement of a direct radiator loudspeaker diaphragm is inversely proportional to the square of its signal frequency. The lowest frequency of a flat response is restricted by the diaphragmfs fundamental resonance frequency. Therefore, a loudspeaker diaphragm for radiation of a low‐frequency signal shall have large amplitude and low resonant frequency. The authors propose the application of a piezoelectric ultrasonic motor for this purpose. It produces a completely controlled large output force because its output mechanical impedance is much greater than any conventional transducer or motor. An ultrasonic motor whose stator is connected to a direct‐radiator loudspeaker cone diaphragm by a rod and whose rotor is loaded by a heavy metal ring rotates with a constant velocity. Modulation of the velocity by the audio signal causes driving force to the diaphragm because a heavy ring with large inertia tends to rotate with constant velocity. This paper reports construction of a practical experimental mo...