报告题目：Applications of bulk-PZT in microsystems:
Microassembly & Micro-beam resonant transduction
报告人： Dr. Serhan Ardanuç
时 间： 2015年11月12日（星期四）10:00am-11:00am
地 点： 中山大学东校区软件学院A101讲学厅
Abstract: The operation of most microsystems can be reduced down to one or more kinds of transduction (sensing and actuation) mechanisms. As such, piezoelectric materials, which provide a reciprocal platform for electrical to mechanical energy conversion, find wide-spread use in Microelectromechanical Systems (MEMS). While piezoelectric layers with thicknesses less than a few microns can be deposited using sputtering or sol-gel deposition, applications that require larger forces or strokes often require thicker layers. One of the fundamental limitations of using a common, high-quality, piezoelectric materials such as lead zirconium titanium oxide (Pb(Zr1−x,Tix)O3, PZT) within a microsystem is the high sintering temperatures exceeding 1000ºC. At these high temperatures severe reaction and diffusion occurs between PZT and silicon, which is one of the most common elements in microsystems. This limitation can be overcome by using off-the-shelf, high-quality bulk-PZT, which is optimally manufactured and sintered. Despite the challenges of bonding and hybrid integration, many microsystems such as medical ultrasonic imaging arrays, microfluidic mixers, separators, pumps, and ultrasonic motors commonly use bulk-PZT transduction.
In this talk, electromechanical modeling, actuation, and sensing aspects of bulk-piezoelectric transduction are investigated within the context of their applications to microsystems. In the first part of the talk, I describe the bidirectional energy exchange between surface-micromachined beams and bulk-lead zirconium titanate (PZT) actuators attached to the silicon substrate. A small-signal model is used to describe the detection of acoustic waves launched from electrostatically actuated structures on the surface of the die. The same model also describes the actuation of these structures through the elastic waves that are generated by the PZT ceramics. The interaction is modeled via an empirical electromechanical equivalent circuit, which is substantiated by experiments designed to extract the model parameters.
In the second part of the talk, I will introduce Ultrasound Enhanced Electrostatic Batch Assembly (U2EBA) method as a die level application of bulk-PZT for the realization of 3D microsystems. U2EBA involves placing the die in an external DC electric field perpendicular to the substrate and actuating the die with an off-chip, bulk-piezoelectric ceramic. Simplicity of the setup, applicability to a broad range of surface micromachining processes, lack of any additional fabrication steps or unusual materials, and fully off-chip nature that requires no electrical or mechanical contact to the assembled microstructures are the foremost advantages of this method. These attributes distinguish it from other popular assembly methods that rely on surface tension, magnetic coatings, or high-precision micro-tweezers and robotics. Yield rates reaching up to 100% are reported from 8 X 8 arrays of hinged mirrors with dimensions 180x100 μm2.
Introduction on the lecturer: Dr. Serhan Ardanuç is a research associate at Cornell University and a cofounder of Suntomics Inc., an Ithaca, NY based company. His Ph.D. thesis focused on the use of ultrasonically actuated mirror arrays, the basic platform that led to the Solar Tiles (STILEs) used by Suntomics. He received his B.Sc. degree in Electrical and Electronics Engineering from Middle East Technical University (METU), Ankara, Turkey in 2001, and his Ph.D. degree in 2010 from the School of Electrical and Computer Engineering at Cornell University, Ithaca, NY with a minor in theoretical and applied mechanics. As a research associate in the SonicMEMS Group at Cornell University, he works on multiple microelectromechanical systems (MEMS) related projects spanning from reconfigurable ultrasonic communication on chip to microsystems for electron acceleration. Serhan worked as a MEMS-characterization engineer at XEROX Research Center focusing on failure modes of electrostatic ink-jet heads, and as a senior research scientist at METU Micro-Electro-Mechanical Systems Research and Application Center, focusing on novel triboelectric energy harvesting methods. His research interests include array based microsystems, analog/digital circuit design, behavioral/finite-element simulations, applications of embedded, millimeter scale reflector platforms to concentrated solar power harvesting, and ultrasonic transduction of microsystems using piezoelectric materials. Serhan is a co-inventor of the STILE technology along with Dr. Amit Lal and served as the entrepreneurial lead of the NSF I-CORPS award winning team in 2014. He has >25 peer-reviewed publications, 2 patents, and 6 pending patent applications in the field of micro/nano systems, and concentrating solar energy harvesting technologies. Serhan is also a recipient of Cornell McMullen Fellowship and a co-author of the best student paper in 2010 IEEE NEMS Conference and 2014 IEEE Ultrasonic Symposium.