Actuator applications of piezoelectrics started in late 1970s, and enormous investment was in-stalled on practical developments during ‘80s, aiming at consumer applications such as precision positioners with high strain materials, multilayer device designing and mass-fabrication process-es for portable electronic devices, ultrasonic motors for micro-robotics and smart structures. Af-ter the slump due to the worldwide economic recession in late ‘90s, we are now facing a sort of “Renaissance” of piezoelectric actuators according to the social environmental changes. This pa-per reviews the recent advances in materials, designing concepts, and new applications of piezoe-lectric actuators, and describes the future perspectives of this area. The 21st century faces to a “sustainable society”. Global regulations are strongly called on eco-logical and human health care issues, and the government-initiated technology (i.e., “politico-engineering”) has become essential. Because of significantly high energy efficiency of piezoe-lectrics in comparison with other actuators such as chemical engines and electromagnetic com-ponents, piezoelectric actuators have been re-focused most recently in the sustainable society (i.e., “Renaissance” in piezoelectric actuators). I will discuss five key trends in this paper for providing the future perspectives; “Performance to Reliability”, “Hard to Soft”, “Macro to Nano”, “Homo to Hetero” and “Single to Multi-functional”. First in the materials trend, the worldwide toxicity regulation is accelerating the de-velopment of Pb-free piezoelectrics for replacing the conventional PZTs. Second, high power piezoelectrics with low loss have become a central research topic from the energy-efficiency im-provement viewpoint; that is to say, “real (strain magnitude) to imaginary performance (heat generation reduction)”. Third, we are facing the revival polymer era after ‘80s because of their elastically soft superiority. Larger, thinner, lighter and mechanically flexible human interfaces are the current necessity in the portable electronic devices, leading to the development in elas-tically soft displays, electronic circuits, and speakers/microphones. Polymeric and polymer-ceramic composite piezoelectrics are reviving and commercialized. PZN-PT or PMN-PT single crystals became focused due to the rubber-like-soft piezo-ceramic strain after 25 years of the dis-covery. In the MEMS/NEMS area, piezo MEMS is one of the miniaturization targets for inte-grating the piezo-actuators in a micro-scale devices, aiming at bio/medical applications for main-taining the human health. “Homo to hetero” structure change is also a recent research trend: Stress-gradient in terms of space in a dielectric material exhibits piezoelectric-equivalent sensing capability (i.e., “flexoelectricity”), while electric-field gradient in terms of space in a semicon-ductive piezoelectric can exhibit bimorph-equivalent flextensional deformation (“monomorph”). New functions can be realized by coupling two effects. Magnetoelectric devices (i.e., voltage is generated by applying magnetic field) were developed by laminating magnetostrictive Terfenol-D and piezoelectric PZT materials, and photostriction was demonstrated by coupling photovolta-ic and piezoelectric effects in PLZT. In the application area, the global regime for “ecological sustainability” particularly accelerated new developments in ultrasonic disposal technology of hazardous materials, diesel injection valves for air pollution, and piezoelectric renewable energy harvesting systems.
Kenji Uchino, one of the pioneers in piezoelectric actuators, is Founding Director of International Center for Actuators and Transducers and Professor of EE and MatSE at Penn State University. He was Associate Director (Global Technology Awareness) at The US Office of Naval Research – Global Tokyo Office as IPA from 2010 till 2014. He was also the Founder and Senior Vice President & CTO of Micromechatronics Inc., State College, PA. After being awarded his Ph. D. degree from Tokyo Institute of Technology, Japan, he became Research Associate/Assistant Professor (1976) in Physical Electronics Department at this university. Then, he joined Sophia University, Japan as Associate Professor in Physics Department in 1985. He was then recruited from The Penn State University in 1991. He was also involved with Space Shuttle Utilizing Committee in NASDA, Japan during 1986-88, and Vice President of NF Electronic Instruments, USA, during 1992-94. He was the Founding Chair of Smart Actuators/Sensors Committee, Japan Technology Transfer Association sponsored by Ministry of Economics, Trading and Industries, Japan from 1987 to 2014, and is a longterm Chair of International Conference on New Actuators, Messe Bremen, Germany since 1997. He was also the associate editor for Journal of Advanced Performance Materials, J. Intelligent Materials Systems and Structures and Japanese Journal of Applied Physics. Uchino served as Administrative Committee Member (Elected) of IEEE Ultrasonics, Ferroelectrics and Frequency Control (1998-2000) and as Secretary of American Ceramic Society, Electronics Division (2002-2003). His research interest is in solid state physics, especially in ferroelectrics and piezoelectrics, including basic research on theory, materials, device designing and fabrication processes, as well as application development of solid state actuators/sensors for precision positioners, micro-robotics, ultrasonic motors, smart structures, piezoelectric transformers and energy harvesting. K. Uchino is known as the discoverer/inventor of the following famous topics: (1) lead magnesium niobate (PMN)-based electrostricive materials, (2) cofired multilayer piezoelectric actuators (MLA), (3) superior piezoelectricity in relaxor-lead titanate-based piezoelectric single crystals (PZN-PT), (4) photostrictive phenomenon, (5) shape memory ceramics, (6) magnetoelectric composite sensors, (7) transient response control scheme of piezoelectric actuators (Pulse-Drive technique), (8) micro ultrasonic motors, (9) multilayer disk piezoelectric transformers, and (10) piezoelectric loss characterization methodology. On-going research projects are also in the above areas, especially in the last three items (8), (9) and (10) most recently. He has authored 501 papers, 68 books and 31 patents in the ceramic actuator area. 30 papers/books among his publications have been cited more than 100 times, leading to his average h-index 56. Total citation number 18,000 and annual average citation number 400 are very high in College of Engineering. He was also awarded his MBA degree from St. Francis University (2008), and authored a textbook, “Entrepreneurship for Engineers” for College of Business. He is a Fellow of American Ceramic Society since 1997, a Fellow of IEEE since 2012, and also is a recipient of 27 awards, including IEEE-UFFC Ferroelectrics Recognition Award (2013), Inventor Award from Center for Energy Harvesting Materials and Systems, Virginia Tech (2011), Premier Research Award from The Penn State Engineering Alumni Society (2011), the Japanese Society of Applied Electromagnetics and Mechanics Award on Outstanding Academic Book (2008), SPIE (Society of Photo-Optical Instrumentation Engineers), Smart Product Implementation Award (2007), R&D 100 Award (2007), ASME (American Society of Mechanical Engineers) Adaptive Structures Prize (2005), Outstanding Research Award from Penn State Engineering Society (1996), Academic Scholarship from Nissan Motors Scientific Foundation (1990), Best Movie Memorial Award at Japan Scientific Movie Festival (1989), and the Best Paper Award from Japanese Society of Oil/Air Pressure Control (1987). He is also one of the founding members of Worldwide University Network, which encourages the linking between the UK and US multiple universities since 2001.