14 March 2013
Our main research focuses on the following two fields: inertial navigation technology and micro aerial vehicles (MAVs). The inertial navigation technology that we are researching includes gyroscopes, accelerators and inertial measurement units (IMUs). The aim of our team is to achieve the miniaturisation of non-silicon devices while keeping good characteristics. Traditional devices meet some problems during miniaturisation, and some devices based on the new methods will be coming through in the next few years.
A MEMS piezoelectric concentrated-mass BAW resonator based on an out-of-plane degenerate mode for a micro angular detector is reported in our Letter. The structure combines the BAW driving/sensing with a rocking concentrated mass, to increase the proof mass and the resonant frequency of the resonator. This device is fabricated by a simple MEMS process, and demonstrates good characteristics during mode testing. Without any tuning methods, the device works at the high resonant frequency of 173.8 kHz, with a small frequency split (about 200 Hz), and also achieves a high Q factor.
First, the result proves that devices with good characteristics can be achieved with non-silicon MEMS technology. And, as the processing accuracy increases, in the right circumstances it will have a better performance than that of silicon MEMS technology. Second, the device works at a new BAW out-of-plane degenerate mode, which is named ‘the rocking mode’. The design innovatively combines the BAW drive and sense with a rocking concentrated mass. Third, piezoelectric materials are used as the resonator rather than the power transducer. This design can increase the signal heavily. Finally, the test result confirms that the device could have a high Q factor with a wide bandwidth, so the response time and the sensitivity of the sensor would be highly predicted.
The device could be used in the field, such as in automobile and consumer electronics. It could be used as a micro angular detector or a gyroscope. When the device is designed to be even smaller and produced on the assembly line in the near future, the size and cost of the device could meet the demands of being used in a mobile phone. Alternatively, the device could be used as a resonator. When the device is made even more miniature, it could be used as a micro filter, and used in the ultrasound and communication fields.
At the moment we are continuing the testing work, and we expect that more data and results will be published in the near future. We anticipate that the introduction of a better piezoelectric material to a device with a better Q-factor will allow even better performances. At the same time, the driving and sensing circuit could be integrated on the wafer, to decrease the signal error. These works are significant, and there are many issues to be overcome.
As the Internet of the things develops, gyroscopes and accelerators will start to have broad application prospects. However, the Internet of the things is very complex so the needs for the devices are much more complex and diverse. In the coming years, devices based on different principles and different structures will be developed to meet this demand, and they will have made huge progress on the fields of low-cost and miniaturisation.
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