Title CMUT: Theory, Fabrication, and Applications
Instructor(s) and Affiliation  PKhuryYakub B. T. Khuri-Yakub, Stanford University

MarioKupnik M. Kupnik, Technische Universität Darmstadt

 OmerOralkan O. Oralkan, North Carolina State University

Short biography of instructor(s) Butrus (Pierre) T. Khuri-Yakub is a Professor of Electrical Engineering at Stanford University. He received the BS degree from the American University of Beirut, the MS degree from Dartmouth College, and the Ph.D. degree from Stanford University, all in electrical engineering. His current research interests include medical ultrasound imaging and therapy, ultrasound neuro-stimulation, chemical/biological sensors, gas flow and energy flow sensing, micromachined ultrasonic transducers, and ultrasonic fluid ejectors. He has authored over 600 publications and has been principal inventor or co-inventor of 97 US and international issued patents. He was awarded the Medal of the City of Bordeaux in 1983 for his contributions to Nondestructive Evaluation, the Distinguished Advisor Award of the School of Engineering at Stanford University in 1987, elected Fellow of the IEEE in 1995, the Distinguished Lecturer Award of the IEEE UFFC society in 1999, a Stanford University Outstanding Inventor Award in 2004, Distinguished Alumnus Award of the School of Engineering of the American University of Beirut in 2005, Stanford Biodesign Certificate of Appreciation for commitment to educate mentor and inspire Biodesgin Fellows in 2011, recipient of IEEE Rayleigh award 2011, and elected Fellow of the AIMBE in 2015.

Mario Kupnik received a degree in Engineering from Graz University of Technology, Austria, in 2000, and a Ph.D. degree from the University of Leoben, Austria, in 2004, both in electrical engineering. From 2005-2011 he was a Postdoctoral Researcher, Research Associate and Senior Research Scientist in the group of Prof. Khuri-Yakub at the Edward L. Ginzton Laboratory, Stanford University, USA. Prior to his Ph.D. studies (2000-2004), he was with Infineon Technologies AG, Graz, Austria, working as an Analog Design Engineer in the field of ferroelectric memories and contactless smart card systems (RFID). From March 2011 to December 2014 he was Professor of Electrical Engineering at Brandenburg University of Technology, Cottbus, Germany. Since January 2015, he is a Professor at the Technische Universität Darmstadt, Germany, heading the Measurement and Sensor Technology Group. His research interests are on ultrasonic gas flow meters, including modelling the sound propagation in harsh environment conditions, micromachined air-coupled ultrasonic transducers with a focus on elevated temperatures, low frequency phased arrays for air-coupled ultrasound, biological/chemical sensing in liquids, modelling and fabricating capacitive micromachined ultrasonics transducers (CMUTs) and applying these devices for various sensory applications.

Ömer Oralkan received the B.S. degree from Bilkent University, Ankara, Turkey, in 1995, the M.S. degree from Clemson University, Clemson, SC, in 1997, and the Ph.D. degree from Stanford University, Stanford, CA, in 2004, all in electrical engineering. Dr. Oralkan was a Research Associate (2004-2007) and then a Senior Research Associate (2007-2011) in the E. L. Ginzton Laboratory at Stanford University. In 2012, he joined the Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, as an Associate Professor. His current research focuses on developing devices and systems for ultrasound imaging, photoacoustic imaging, image-guided therapy, biological and chemical sensing, and ultrasound neural stimulation. Dr. Oralkan is an Associate Editor for the IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control and serves on the Technical Program Committee of the IEEE Ultrasonics Symposium. He received the 2013 DARPA Young Faculty Award and the 2002 Outstanding Paper Award of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society. Dr. Oralkan has authored more than 140 scientific publications.

Abstract This course provides basic knowledge and understanding of capacitive micromachined ultrasonic transducers (CMUTs) and their applications.

After a short background discussion of previous implementations of capacitive ultrasonic transducers, we will provide all the information necessary for the successful design of a CMUT: The simple parallel plate capacitor transducer and its electrical equivalent circuit model will be explained in detail, including the derivation of all essential design equations, and the theoretical device performance limits. Developing an approximate analytical model that better represents the realizable membrane of a CMUT follows this. A motivation for a more sophisticated finite element model is given, and the key techniques of finite element analysis based CMUT designs are explained and demonstrated using brief examples. Next, we compare and contrast CMUTs that are designed for airborne and immersion applications. Only for immersed operation the periodic structure of a CMUT array needs to be considered to minimize parasitic cross-talk effects. Two acoustic cross-talk modelling techniques will be discussed for that purpose.

Then, the two main CMUT fabrication techniques, i.e. sacrificial release and direct wafer bonding, are explained and compared to each other. Next, we discuss device characterization that will cover electrical, mechanical and ultrasonic measurements: optical interferometer, electrical input impedance, output pressure; receive sensitivity, impulse response and dynamic range. As part of the electrical characterization we will discuss the design and implementation of low noise front-end electronics and the need for their integration in the vicinity of the CMUT.

In addition to an overview of several CMUT applications, we conclude the course by giving two detailed design examples, one for an airborne device for chemical/biological sensing applications and one for medical imaging applications.

Overview of topics covered Capacitive micromachined ultrasonic transducers, micro electro mechanical systems, finite element modeling, applications in immersion (medical imaging, therapy, and neuro-modulation) and air or gas.
Target audience Graduate students, transducer engineers, and UFFC members with interest in transducers for various ultrasound applications.