Search

In this paper, we present the observation results of the surface potential of micropattemed thick (> 1 pm) self-assembled electrets (SAEs) for MEMS vibrational energy harvesters (VEHs). To evaluate the surface potential of micropattemed SAEs, we propose and develop test devices with removable through-hole substrates corresponding to the moving electrodes of SAE-MEMS VEHs. In this study, SAEs are deposited simultaneously on two test devices with different through-hole spacings and on a reference flat substrate using the same vacuum evaporation process. The surface potential of SAEs is proportional to the film thickness, and when the film thickness of the SAE deposited on the flat substrate is 4.48 pm, the surface potential exceeds 200 V. At this time, in a test device where the average thickness of micropattemed SAEs is 3.08 pm, the measured surface potential is 68 V. In addition, it is experimentally observed that when micropattemed SAEs are formed using the through-hole structures, the microfabrication process causes the SAE pattern to spread wider than the through-hole dimensions, and the surface profiles are not flat. These findings provide useful insights for the design of SAE-MEMS VEHs using micropattemed SAEs with through-hole structures. [ABSTRACT FROM AUTHOR]

Objective. To evaluate the effectiveness of radiation protective curtains in reducing the occupational radiation exposure of medical personnel. Methods. We studied medical staff members who had assisted in 80 consecutive therapeutic endoscopic retrograde cholangiopancreatography (ERCP) procedures. Use of radiation protective curtains mounted to the X-ray tube was determined randomly for each procedure, and radiation doses were measured with electronic pocket dosimeters placed outside the protective apron. Results. When protective curtains were not used, the mean radiation doses to endoscopists, first assistants, second assistants, and nurses were 340.9, 27.5, 45.3, and 33.1 μv, respectively; doses decreased to 42.6, 4.2, 13.1, and 10.6 μv, respectively, when protective curtains were used (P < 0.01). When the patient had to be restrained during ERCP (n = 8), the radiation dose to second assistants without protective curtains increased by a factor of 9.95 (P < 0.01) relative to cases in which restraint was not required. Conclusions. During ERCP, not only endoscopists, but also assistants and nurses were exposed to high doses of radiation. Radiation exposure to staff members during ERCP was reduced with the use of protective curtains. [ABSTRACT FROM AUTHOR]