A dual-planar-coil miniature dynamic microphone, one of the electro-acoustic transducers working with the principle of the electromagnetic induction, has been realized by semiconductor micro-processing and micro-electro-mechanical system (MEMS) techniques. This MEMS microphone mainly consists of a 1 μm thick diaphragm sandwiched by two spiral coils and vibrating in the region with the highest magnetic flux density generated by a double magnetic system. In comparison with the traditional dynamic microphone, besides the miniaturized dimension, the MEMS microphone also provides 325 times the vibration velocity of the diaphragm faster than the traditional microphone. Measured by an audio analyzer, the frequency response of the MEMS microphone is only 4.5 dBV Pa −1 lower than that of the traditional microphone in the range between 50 Hz and 20 kHz. The responsivity of −54.8 dB Pa −1 (at 1 kHz) of the MEMS device is competitive to that of a traditional commercial dynamic microphone which typically ranges from −50 to −60 dBV Pa −1 (at 1 kHz).

This work develops a new technology to fabricate polymer-dispersed microencapsulated liquid crystal (PDMLC) devices using screen-printing, which is a low temperature procedure (about 90 degrees C) for application on a soft plastic substrate. This research demonstrates numerically and in Mandarin, a 4.5-in multicolor PDMLC (MPDMLC) device with high color contrast, low electric consumption and flexible bending mechanical property. The current work coats three different color pastes (red, blue and black) on a single substrate. Their turn-on voltages are all as low as 5 V and saturation voltages are 20, 30, and 30 V for red, blue, and black colors, respectively

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