Shalabi Nabil, Searles Kyle, Takahata Kenichi
Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC V6T 1Z4 Canada.
School of Biomedical Engineering, University of British Columbia, Vancouver, BC V6T 1Z3 Canada.
Microsyst Nanoeng. 2022 Dec 23;8:132. doi: 10.1038/s41378-022-00469-w. eCollection 2022.
Switch mode capacitive pressure sensors are proposed as a new class of microfabricated devices that transform pressure into a mechanically switching capacitance to form an analog-to-digital signal with zero power, high sensitivity, and a high signal-to-noise ratio. A pressure-sensitive gold membrane suspended over a capacitive cavity makes ohmic contact with patterned gold leads on the substrate, closing circuits to fixed on-chip capacitors outside the cavity and leading to significant step responses. This function is achieved by allocating the switch leads on the part of the counter electrode area, while the remaining area is used for touch mode analog capacitive sensing. The sensor microchip is prototyped through a novel design approach to surface micromachining that integrates micro-Tesla valves for vacuum sealing the sensor cavity, showing an unprecedented response to applied pressure. For a gauge pressure range of 0-120 mmHg, the sensor exhibits an increase of 13.21 pF with resultant switch events, each of which ranges from 2.53-3.96 pF every 12-38 mmHg, in addition to the touch mode linear capacitive increase between switches. The equivalent sensitivity is 80-240 fF/mmHg, which is 11-600× more than commercial and reported touch mode sensors operating in similar pressure ranges. The sensor is further demonstrated for wireless pressure tracking by creating a resonant tank with the sensor, showing a 32.5-101.6 kHz/mmHg sensitivity with frequency jumps led by the switch events. The developed sensor, with its promising performance, offers new application opportunities in a variety of device areas, including health care, robotics, industrial control, and environmental monitoring.
开关模式电容式压力传感器被提议作为一类新型的微加工器件，它将压力转换为机械开关电容，以形成具有零功耗、高灵敏度和高信噪比的模拟到数字信号。一个悬浮在电容腔上方的压敏金膜与基板上的图案化金引线进行欧姆接触，闭合电路连接到腔体外的固定片上电容器，并导致显著的阶跃响应。此功能通过在对电极区域的一部分上分配开关引线来实现，而其余区域用于触摸模式模拟电容传感。传感器微芯片通过一种新颖的表面微加工设计方法进行原型制作，该方法集成了用于真空密封传感器腔的微特斯拉阀，对施加的压力表现出前所未有的响应。对于0 - 120 mmHg的表压范围，除了开关之间的触摸模式线性电容增加外，传感器在产生开关事件时电容增加13.21 pF，每个开关事件在每12 - 38 mmHg范围内变化2.53 - 3.96 pF。等效灵敏度为80 - 240 fF/mmHg，比在类似压力范围内工作的商业和已报道的触摸模式传感器高11 - 600倍。通过与传感器创建一个谐振回路，进一步证明了该传感器可用于无线压力跟踪，在开关事件导致的频率跳变下，灵敏度为32.5 - 101.6 kHz/mmHg。所开发的传感器具有良好的性能，在包括医疗保健、机器人技术、工业控制和环境监测等各种设备领域提供了新的应用机会。
