© Fraunhofer IPMS
New applications for ultrasound technology through CMUTs
Anartz Unamuno
26-09-2013
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 2
Agenda Capacitive Micromachined Ultrasonic Transducers (CMUT)
• What is ultrasound
• 1o1 ultrasound transducers
• Comparison Piezoelectric & CMUT
• History of CMUTs
• Challenges CMUT & IPMS
• Strengths, Weaknesses, Opportunities, Threads
• Initial results of IPMS CMUTs
• Current research for CMUT applications (worldwide)
• Conclusion
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 3
What is ultrasound?
Sample applications:
Medical imaging
Non-destructive testing
Level sensors
Speed sensors
Etc… T.G. Leighton / Progress in Biophysics and Molecular Biology 93 (2007) 3–83
Images form Wikipedia search: Ultrasound
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 4
1o1 -- Ultrasonic transducers
Oralkan O., 2002
Capacitve Micromachined Ultrasonic Transducer
Piezoelectric Transducer
Image form Wikipedia search: Piezoelectricity
Mechanical displacement generates US waves
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 5
Advantages -- Piezoelectric & CMUTs transducers
Piezoelectric CMUT
Accepted technology CMOS integration
Reliability(*) Batch production – reduced cost
Output acoustic pressure(*) RoHS compatible
Tight parameter specification
High temp. capable (ca. 800 ºC)
Scalability (size, shape, array, 2D)
Axial resolution
(*) Two factors that need to be addressed on CMUTs
Solving these two, CMUTs should be a winning technology!
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 6
History of CMUTs
Khuri-Yakub, http://www-kyg.stanford.edu/khuriyakub/opencms/en/research/cmuts/History/index.html
A MEMS device researched over the last 20 years
But no products on Euro nor US market using CMUTs yet!!
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 7
Challenges of fabricating CMUTs matches Fraunhofer IPMS expertise
Many issues have been previously solved at IPMS
Requirement Fraunhofer IPMS has marketed product
Large arrays of MEMS elements with quasi-identical performance
High voltage drive for capacitive MEMS
Low noise amplifiers or receive side
Integration MEMS-CMOS
Material expertise (process control)
Testing capabilities
Infrastructure to access and service small-to-medium size customers
US system integration
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 8
Testable CMUT devices
Work at IPMS -- Electrically testable 1D CMUT array
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 9
Work at IPMS -- Electrical impedance measurement
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 10
Resonance frequency spread, SD = 17 kHz (62 array elements)
Work at IPMS -- Resonance frequency distribution
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 11
Applications – Intra Vascular UltraSound (IVUS)
Khuri-Yakub, 2009
Degertekin, 2012
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 12
Applications – Harsh environment
Reference 1
High Temperature
High Pressure
1. Kupnik et Al., US patent 7,843,022 2. M.-C. Ho, M. Kupnik, K. K. Park, K. Eckhoff, and B. T. Khuri-Yakub, “Wide pressure range
operation of air-coupled CMUTs,” in Proc. IEEE Ultrasonics Symposium, pp. 93-96, 2012.
Reference 2
Reference 2
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 13
Applications – Chemical sensors
Almira Ramanaviciene, Darius Virzonis, Gailius Vanagas and Arnas Ramanavicius, “Capacitive micromachined ultrasound transducer (cMUT) for immunosensor design“, Analyst, 2010, 135, 1531 DOI: 10.1039/c0an00104j
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 14
Applications – Neural stimulation
1. Omer Naor et al, “Towards multifocal ultrasonic neural stimulation II: design considerations for an acoustic retinal prosthesis“, J. Neural Eng. 9 026006, 2012
2. Menz, Michael D - Oralkan, Omer - Khuri-Yakub, Pierre T - Baccus, Stephen A, “ Precise neural stimulation in the retina using focused ultrasound“, The Journal of neuroscience: the official journal of the Society for Neuroscience, Vol. 33, No. 10
Reference 1
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 15
Conclusions
• CMUTs enable novel ultrasonic applications
• CMUTs should not be seen as a replacement for pezoelectric transducers, but they are the only option in some applications (e.g. High temp, large 2D array integration, etc.)
• Technology is reaching a mature state to be deployed to the markets.
• IPMS has one of the few fabrication facilities around the world, where it is possible to produce large MEMS arrays at tight tolerances.
• Several team around the Globe are developing clever applications to make use of the CMUT capabilities.
© Fraunhofer IPMS
Anartz Unamuno I 26.09.2013 I slide 16
Thanks!