In this study, we successfully designed and tested a new micropump that utilizes an active check valve and bottom-protruding structure to achieve sample transportation. We performed theoretical analyses and numerical simulations to determine the optimal location of the active check valve. We also experimentally analyzed variations in the generated flow rate with respect to the pneumatic frequencies, actuated air pressures, and locations of the active check valve. The experimental results indicate the optimum air pressure, driving frequency, and location of the active check valve to be 68.9 kPa, 26.0 Hz, and 2.0 mm, respectively. We obtained a maximum pumping rate of 488 μL/min and a maximum pumping efficiency of 35.4%. The proposed micropump could perform a crucial function in the transportation of microfluids and could be incorporated into micro total analysis systems.
This paper presents the world’s smallest inset permanent magnet synchronous motor (PMSM) with a soft magnetic composite (SMC) core, providing ease of manufacturing for micromachine applications without silicon steel laminations. The inset motor can offer an additional reluctance torque and higher torque density with a lower usage amount of permanent magnet. A 15 mm diameter inset motor was developed with the thickness of a tile-type permanent magnet which is limited to 1 mm by the manufacturer. The motor was designed with high torque density and low torque ripple by varying the interpole iron width for the rotor. Two inset motors were made using both SMC and silicon steel materials for comparison. The performance of the SMC motor was inferior to the silicon steel motor, but it still meets the specifications of the commercial market. If the thickness of the tile-type permanent magnet is further reduced, the micro inset motor with a SMC core can be easily mass-manufactured using powder sintering.
A polymer-based capacitive micromachined ultrasonic transducer (CMUT) is developed to measure surface roughness. The transducer is designed with two groups in a ratio of two to one. By using air-coupled ultrasound, the transducer can evaluate surface roughness in five modes: full transmission/ full reception, majority transmission/ majority reception, majority transmission/ minority reception, minority transmission/ majority reception, and minority transmission/ minority reception. Experimentation shows the CMUT can identify the surface roughness using a sample of sandpaper with surface roughness Rrms ranging from 11.4μm to 179.8μm. The results indicate that the full transmission/ full reception mode has maximum signal output and the minority transmission/ majority reception mode can obtain a good signal output with a better energy efficiency rating.
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