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Acoustic MEMS

The Acoustic MEMS research group harnesses acoustic waves manipulated on a microfabricated chips for a broad range of applications that include next-generation fast computation, ultrasound imaging and non-destructive testing, gesture recognition, sound generation and perception, wireless power delivery, cell & particle manipulation on lab-on-chips, ultra-low power wake-up sensors for Internet-of-things (IoTs), wireless passive sensors for environmental monitoring, high frequency piezoelectric resonators for ultra-low power wireless communications for IoT.


Piezoelectric Micromachined Ultrasonic Transducers (PMUT)

The use of ultrasound is familiar to all, especially in a medical context as well as structural health monitoring. Existing ultrasound applications are enabled by traditional bulk transducers. IME is working on creating the next generation of ultrasound transducers that can be fabricated at large scale using semiconductor wafer technology. Known as PMUTs, these devices are based on flexible membranes that are driven electrically by piezoelectric action to generate ultrasound as well as to sense ultrasonic echos. Benefits of PMUTs for ultrasonic sensing include power reduction, miniaturization, and the possibility of tighter integration with interface electronics to ride on benefits of digitalization and AI. IME has capabilities to process AlN, Sc-doped AlN (15% and 20% demonstrated to date) as well as PZT to address a broad range of needs. Applications of PMUTs include non-destructive testing, proximity sensing, imaging, remote environment sensing, as well as power delivery. 

 

Ultra-Low Power Wake-up Sensor Switch

With the growth of interest in IoTs, there has been extensive research on IoT sensor nodes for monitoring abnormal changes in urban environments. Most IoT sensor nodes to date depend on always-on sensors, which consume µW of stand-by power. This amount of power is a significant portion of the total power budget of an IoT sensor node. Therefore, even if an IoT node uses existing low power IC components to build the hardware, it is very difficult to extend the lifetime of the IoT node over one year due to the stand-by power consumption. To address this issue, IME has developed MEMS contact switches that can extend the battery lifetime of IoT sensor nodes to over 10 years. These switches have an almost zero-power consumption in the off-state, but they can sense environmental vibrations, sounds, temperatures, or pressures and wake up the entire IoT node if the signal exceeds a predefined threshold. In this way, the standby power consumption of a IoT node can be cut down to nW levels, and the lifetime is elongated to more than 10 years.


Piezoelectric Over Silicon-On-Nothing (PSON) Platform

Suspended form of piezoelectric MEMS devices has been realized as frequency references for wireless communication, piezoelectric micromachined ultrasonic transducers (pMUTs) for gesture recognition, ultrasonic imaging, fingerprint scanning and acoustofluidic sensors for biological cell manipulation. Conventional methods to fabricate such suspended structures include etching a port on the backside of a silicon-on-insulator (SOI) wafer and cavity-SOI wafers, where a cavity is etched into a substrate wafer and thereafter bonded to another wafer to form a sealed cavity. While backport etching on SOI wafers are generally limited to larger cavities with low densities, cavity-SOI comes at a higher cost with lower yield.