When PMUT and CMUT generate an echo in medical imaging

Six years after the first “on-a-chip technology” point-of-care ultrasound (POCUS) probe for medical imaging, the company Exo (pronounced “Echo”) has recently announced the availability of its first medical point-of-care ultrasound imaging product.

Based on his MEMS & sensing expertise and industry knowledge, Jérome Mouly, Director, Photonic & Sensing division at Yole Intelligence, delivers today a follow-up of this announcement. What is the impact of this innovation on the medical ultrasound industry? What can we expect in terms of business opportunities?

Enjoy reading this snapshot based on the following Yole Intelligence’s products: Status of the MEMS industryUltrasound sensingButterfly Network iQ CMUT Sensor. Yole Intelligence is a Yole Group company.

What differentiates the Exo probe and the initial POCUS probe from Butterfly Network iQ CMUT Sensor? Both are micromachined ultrasound devices based on different transducer principles. Exo has based its development efforts on PMUT (Piezoelectric Micromachined Ultrasound Transducer), while Butterfly Network developed CMUT (Capacitive Micromachined Ultrasound Transducer).

For years, ultrasound transduction was based on bulk piezoelectric ceramic (PZT) as the major and proven technology. It is still the dominant technology, and generated a market of more than $5.5 billion in transducers in 2022, according to the Ultrasound sensing report from Yole Intelligence, published in 2023.

Jérôme Mouly Director, Photonics & Sensing Division at Yole Intelligence, part of Yole Group.
Using MEMS processes, MUT technology (either CMUT or PMUT) enables semiconductor-based devices with a very high density of transducers (MUT array), broader frequency bandwidth than bulk PZT-based devices, serial processing, and higher reproducibility. It also offers better footprint optimization and higher AI/ML integration at the edge.

In total, the ultrasonic MEMS market in 2022 was estimated at  $480 million and will grow to $977 million in 2028. During this period, the CAGR will be 11%, according to the Status of the MEMS Industry report, 2023 edition, including MUT fingerprint sensing for consumer, automotive, and medical applications.

Exo has spent more than ten years in development and received about $300 million in funding to develop the Exo IRIS probe, competing in the medical imaging market with GE Healthcare, Philips, and Butterly Network. The advantage of the Exo and Butterfly Network probe is the “all-in-one” solution, which can work for different medical imaging applications, including skeletal, cardiovascular, organ,… with only one probe, whereas conventional ultrasound imaging requires different probes for different frequency ranges. Along with AI, it allows an easy and affordable tool to be used by physicians or nurses at the point of care for any situation, such as an examination at a local doctor’s practice, emergency, ICU, or location far from a hospital or any medical structure.

But Exo has not only chosen MUT technology but the Piezo-based detection principle, compared to the capacitive detection principle chosen by Butterfly Network and Fujifilm (former Hitachi Medical Unit). PMUT and CMUT have their own specificities in terms of manufacturing processes and have structured their own supply chain.

Various approaches can be used to get a high integration ratio, low power, and low noise transducer.

  • PMUT uses a MEMS above IC approach, allowing monolithic integration with low parasitic capacitance. This approach is well suited to high-volume applications.
  • On the other hand, the use of Piezo material is a possible challenge in terms of material choice and deposition process. From AlN to PZT, no material offers both good sensing and actuating capabilities. A doped material like Sc-AlN is a “good enough” choice, while PZT is a very good actuator to generate ultrasound waves despite being a non-friendly material for a cleanroom environment.

Without a doubt, the new competition in handheld probes between PMUT and CMUT is now starting. Yole Group is continuously investigating the MEMS industry and monitoring the trends in each market segment. These analyses are combined with multiple teardowns to get a deep understanding of the technologies and the strategic choices made by the leading companies.

About the author

Jérôme Mouly is Director of the Photonics & Sensing Division at Yole Intelligence, part of Yole Group.

Jérôme manages the expansion of the team’s technical expertise and market know-how. In addition, he focuses on the management of business relationships with company leaders and the development of market research and strategy consulting activities.

Jérôme has conducted more than 100 marketing and technological analyses for industrial groups, start-ups, and institutes in the field of MEMS and sensing technologies.

Jérôme has also been deeply engaged in Yole’s finance activities with a dedicated focus on the commercial exploitation of smart system technologies and access to funding opportunities.

Jérôme is regularly involved in international conferences, with presentations and keynotes.

Jérôme Mouly earned a Master of Physics from the University of Lyon (FR).