Piezoelectricity and Flexoelectricity in Solid and Soft Materials

Friday, March 25, 2011 3:00 pm – 4:00 pm
Room 610, M&M Building

Dr. John Y. Fu
Department of Mechanical and Aerospace Engineering
State University of New York

Abstract

Historically, the study of flexoelectricity is closely related to that of piezoelectricity though the physicalmechanisms behind these phenomena are completely different [1]. In solid dielectrics, bothpiezoelectricity and flexoelectricity can be derived from the energy coupling in crystalline structures,which are based on equilibrium thermodynamics. However, those phenomena in polymers and liquidcrystals are more complicated due to their complex molecular chains and conformations. Recently, agiant flexoelectric phenomenon has been observed in bent-core nematic liquid crystal elastomers(BCLCEs) [2], which attracts much scientific attention since the nematic phase cannot be regarded asthe ferroelectric phase in most mesomorphic materials. It was believed that the giant flexoelectric effectmight only be observed in certain mesomorphic materials with the chiral smectic C* phase, a ferroelectricphase predicted by Meyer in the 1970s for liquid crystals [3]. Inspired by this study, we investigatedcertain polyvinylidene fluoride (PVDF) polymer films. A giant flexoelectric effect in a PVDF polymer filmwith mixed α- and β-phases has been observed in our group [4], which contradicts the previoustheoretical estimation that the flexoelectric coupling is small, on the order of 10 pC/m. In this seminar, Iwill re-visit the definitions of both piezoelectricity and flexoelectricity in solid dielectrics, and then comparethem with their counterparts in liquid crystals and polymers. Some peculiar physical phenomena relatedto both piezoelectricity and flexoelectricity in polymers will also be discussed. Finally, I will demonstratethat such a giant flexoelectric effect can be exploited to fabricate soft flexoelectric piezoelectriccomposites and devices by using non-piezoelectric soft materials.

References: [1] P. G. de Gennes, Physics of Liquid Crystals (Oxford University Press, London, 1974). [2] J. Hardenet al., Appl. Phys. Lett. 96, 102907 (2010). [3] R. B. Meyer, L. Liebert, L. Strzelecki, P. Keller, J. Phys. Lett. (Paris)36, 69 (1975). [4] J. Y. Fu et al., “Giant flexoelectricity in a polyvinylidene fluoride film”, submitted to Applied PhysicsLetters.

Biography

Dr. John Y. Fu is an assistant professor of mechanical engineering. He came to Buffalo and joined theMAE Department in August 2008. Between 2005 and 2008, Dr. Fu worked as a postdoctoral scholar in a navysponsored materials research laboratory. He completed his college education in China, and received his Ph.D.degree in electrical engineering from the Pennsylvania State University at University Park in December 2004. Dr.Fu holds one American patent and four American and international pending patents. His current research interestsfocus on polymer physics, dielectric polymers, ferroelectric polymers, liquid crystal polymers, flexoelectricpiezoelectric polymer composites and devices, and flexoelectric and flexoviscous phenomena in polymers andbiomaterials.

Future Tech: Nanoscience Improves Flash Memory

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Nanotechnology is a growing field with great potential, and in addition to Nanotech Innovations, Michigan Tech is also home to research being done by faculty and professors. This includes Dr. Yoke Khin Yap, who is studying carbon nanotubes and their applications, Dr. Levy, who is doing research involving photonic wave drives (devices to integrate optics with electricity for computing), as well as Dr. Ming, who is researching the use of nanotubes as batteries for energy storage.

The Pressure Dependence of Pore Morphology in Aluminum Gasarite Metallic Foams Produced by Thermal Decomposition

Friday, March 18, 2011 3:00 pm – 3:30 pm
Room 610, M&M Building

Joe Licavoli
Graduate Student
Materials Science and Engineering
Michigan Technological University

Abstract

Gasarite metallic foams are those in which porosity is elongated due to eithergas-metal eutectic growth or evolution of gas from particulate during chillcasting.  Gasarite foams have several superior properties compared to othermetallic foam types, but in general repeatability of experimental results is amajor issue when studying such systems.  The current study replicatesexperiments conducted by other research groups in which ambient pressurewas varied during chill casting of pure aluminum on titanium hydride.According to ideal gas behavior it is expected that decreasing pressure at aconstant temperature will increase pore size and thus porosity, howeverquasi-boiling conditions and subsequent escape of gases from thesolidification front may nullify this effect.  Additional information provided inthis study includes the velocity profile of the solidification front, vacuumlevels, titanium hydride particle size, microstructure around pores andpackaging of the particulate are reported.  In agreement with previousstudies, it was found that operating under vacuum conditions increasesporosity and the tendency to form columnar pores.  Disagreement has beenfound in the propensity to form pores more than 10mm in length and inuniformity of pore radii.  Potential reasons for this disagreement have beendeduced from micro and macrostructural information.  Further studies andintegration of results into process models will be discussed.

Michigan Tech Graduate Engineering Programs Move Up One Position in US News Rankings

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Michigan Tech’s College of Engineering has moved up in the US News & World Report annual ranking of graduate schools. Tech’s graduate engineering program is ranked 85th in the nation in 2012 rankings released online today. Last year the graduate engineering program overall ranked 86th. Four graduate engineering specialties were ranked in the top 50 nationwide for the second year in a row. Environmental Engineering ranked 28th; Materials Science and Engineering and Mechanical Engineering-Engineering Mechanics each ranked 48th; and Civil Engineering ranked 49th. Their rankings were the same last year.

Design and Application of Bioadhesives Inspired by Marine Mussels

Friday, March 4, 2011 3:30 pm – 4:30 pm
Room G05, Rekhi Hall

Bruce P. Lee
Director of New Technology
Nerites Corporation, Madison, WI

Abstract

Bioadhesives have a wide range of important applications in the biomedical field.  Tissueadhesives simplify complex surgical procedures to achieve effective wound closure and surgicalrepair. Despite these important functions, currently available adhesives seldom meet the basicrequirements for in vivo applications because of possible disease transmission, poor adhesivequality, or toxicity concerns. Thus, there is an ongoing need for the development of tissueadhesives with improved characteristics. Nature provides many outstanding examples ofadhesive strategies from which chemists and materials scientists can draw inspiration in theirpursuit of new biomaterials. Of particular interest is the mussel adhesive protein (MAP) secretedby marine mussels. MAP is initially secreted as a proteinaceous fluid, and then subsequentlyharden in situ to form an adhesive plaque, which allow mussels to bind tenaciously to varioustypes of surfaces underwater. One of the unique structural features of MAP is the presence of L-3,4-dihydroxyphenylalanine (DOPA), an amino acid post-translationally modified from tyrosine,which is believed to fulfill the dual role as the adhesive moiety and the crosslinking precursor.Our research focuses on the incorporation of DOPA and its derivatives in creating syntheticmimics of MAPs for various medical applications. In this seminar, I will discuss the design andapplication of these biomimetic adhesive materials.

SAE Endorses Michigan Tech Hybrid Vehicles Certificate

Michigan Academy for Green Mobility Alliance (MAGMA)

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Through MAGMA, SAE International has approved three graduate certificate programs in hybrid electric vehicles and advanced battery systems. Michigan Tech’s hybrid vehicle engineering certificate, which takes 15 graduate credits to earn, tops the list of programs approved for up to $1,800 in training grants. This is an interdisciplinary program involving faculty and staff from mechanical engineering-engineering mechanics, electrical and computer engineering, materials science and engineering and chemical engineering.