Interview

Abstract

Zongda Hu from the Chinese Academy of Sciences, China, talks to Electronics Letters about his paper ‘Highly sensitive resonant pressure sensor based on mode-localization effect’, page 882. Zongda Hu My field of research is concerned with Micro-Electro-Mechanical System (MEMS) including pressure sensor, accelerometer, gyroscope, and so on. As we all know, MEMS sensors have different advantages with low-power consumption, small volume, and low price in contrast with traditional sensors. I started working in this field whilst pursuing my master's degree in 2012. My tutor, Professor Yu, who has already worked in this field for almost 30 years guides me in this novel area. I appreciate it so much. The most interesting issue is developing a perfect sensor with high sensitivity, high resolution, and long-term stability. The exploration of petroleum and gas resources is the particular application which interests me as the harsh underground environment requires more reliable MEMS sensors. The exploration of petroleum needs pressure sensors to detect the pressure value in the drilling well. By measuring the gradient, the pressure values at different depths in the well can be accurately grasped. The distribution of petroleum is surveyed by measurement. We are aiming to obtain a more sensitive pressure sensor with high signal-to-noise ratio and large dynamic in contrast with traditional sensors which have insufficient precision. We proposed a novel resonant pressure sensor with two mechanically-coupled resonators. We use the amplitude ratios as the readout for the mode-localized sensors, which is different from the traditional resonant sensors using frequency readouts. The measured result shows that the relative sensitivity is two orders higher than traditional resonant sensors. Mode-localization effects which we used in our resonant pressure sensor, can enhance sensitivity greatly in any resonant sensors. This is expected to lead to high resolution, which will minimize the noise impact of the interface circuit. The amplitude-related metrics, such as amplitude ratios, are generally elected as the readout for the mode-localized sensors which is different from the traditional resonant sensors using frequency readouts. However, linear sensing across the veering point is still under investigation due to the inherent loci veering phenomenon. We have to choose a linear sensing range of the amplitude ratios in order to adapt a linear interface circuit system. The mode-localization effect developed in the present research is likely to have a broad technological impact. The present resonant sensor is not famous for its precision, but for its long-term stability. The sensitivity enhanced by mode-localization effect is a key to break the shackles on resonant sensors. The higher the sensitivity of the sensor is, the smaller the effect of circuit noise should be. We can obtain ultra-resolution resonant sensor through this method. In the long term, mode-localization detection method is expected to grow rapidly. Methods based on mode-localization effect have exploded in popularity and real world applications using this method are one of the most recent major breakthrough in some areas, including geological exploration, aerospace, and military industry. As we all know, the temperature in the Earth's crust can reach higher than 200 degrees Celsius. Thermal stress and thermal expansion in normal resonators will cause great measurement deviations. We are planning to focus on designing a micro-mechanical resonator structure that can release thermal stress extremely effectively. Besides, we also take aluminium nitride material into consideration for its good temperature characteristic. Such resonator systems will have sufficient robustness in such a high temperature environment. The current developed trend of MEMS technology is expected to the foreseeable future. This will open up new applications in fields such as the pressure sensor in our cell phone, the accelerometer in the airbags of our cars, and gyroscopes in drone. However, production of MEMS sensors according to design specifications is extremely difficult because the limitations in manufacturing conditions will result in inconsistencies with predictable design. In addition, integrating sensors and circuits is still a big challenge for industrialisation. But I believe that MEMS technology will be the cornerstone for the development of all walks of life in the future.