This Small Business Technology Transfer (STTR) Phase II project will develop a microphone for the test and measurement (T&M) market that utilizes piezoelectric microelectromechanical systems (MEMS) technology. During Phase I of this project, feasibility was demonstrated by building and testing a microphone with the necessary performance for this market. Specifically, this microphone has a noise floor that is 10 times lower than any piezoelectric MEMS microphone previously demonstrated. The unique device modeling and optimization that allowed for this significant performance improvement enables a new class of microphones. During Phase II of this project, the commercialization effort will be accelerated by partnering with a production foundry to develop a fabrication process, enabling the mass fabrication of these parts. Successful completion of this task requires the repeatable fabrication in a production foundry with yield exceeding 90%. This Phase II project also seeks to further develop self-calibration capabilities, building on a unique aspect of these microphones demonstrated during Phase I. Successful completion of this task will result in a microphone capable of determining its own sensitivity to within 1 dB of that determined by standard calibration methods.
The broader impact/commercial potential of this project is significant due to the widespread use of microphones in today's markets. This microphone?s unique combination of device simplicity and high performance enables a new class of microphones that fills the gap between extremely low-cost microphones used in consumer electronics applications and extremely high-cost microphones used in laboratories and test facilities. Through discussions with manufacturers and end-users of microphones and related systems, the company have determined that a wide range of applications would benefit from such a device. These microphones will significantly reduce the cost of complex T&M systems such as arrays that can cost more than $1M and improve the accuracy of equipment used by noise control engineers, work safety inspectors, police officers, and many others. Further, this microphone technology not only has the potential to impact the T&M market, but provides advantages for the hearing aid and consumer electronics markets as well. The total addressable market for this technology is more than $2.5B.
This NSF STTR project has contributed to the advancement of the state-of-the-art in piezoelectric microphone technology. Due to the inherent advantages of piezoelectric transduction over capacitive transduction, the current state-of-the-art in microphones, we expect this to lead to an overall advancement of microphone technology. This award allowed for the development of a new piezoelectric (microelectromechanical systems) MEMS fabrication process for microphones that is more amenable to mass fabrication than previous processes. We are now using the findings from this work to bring up high-volume manufacturing of piezoelectric MEMS microphones. These microphones will have a superior signal-to-noise ratio (SNR), superior matching, and superior particle and water resistance compared to today's capacitive MEMS microphones. These traits make them ideal for a number of emerging uses including directional microphone arrays in smart electronics and acoustic sensing in wearable electronics. They also allow for improved sound quality in devices such as hearing aids and mobile phones. In addition to developing a more robust manufacturing process, this award also helped us develop a self-calibrating microphone. A self-calibrating microphone is especially well suited to applications in which matching is extremely important, such as large arrays. Self-calibrating microphones are also ideal for instrumentation applications where absolute sound pressure level is paramount.