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Marina di Pisa, Italy

Wang H.,Zhejiang University | Wang H.,Harvard University | Cai S.,Zhejiang University | Carpi F.,University of Pisa | And 2 more authors.
Journal of Applied Mechanics, Transactions ASME | Year: 2012

A hydrostatically coupled dielectric elastomer (HCDE) actuator consists of two membranes of a dielectric elastomer, clamped with rigid circular rings. Confined between the membranes is a fixed volume of a fluid, which couples the movements of the two membranes when a voltage or a force is applied. This paper presents a computational model of the actuator, assuming that the membranes are neo-Hookean, capable of large and axisymmetric deformation. The voltage-induced deformation is described by the model of ideal dielectric elastomer. The force is applied by pressing a rigid flat punch onto one of the membranes over an area of contact. The computational predictions agree well with experimental data. The model can be used to explore nonlinear behavior of the HCDE actuators. © 2012 American Society of Mechanical Engineers.

Carpi F.,University of Pisa | Carpi F.,Technology and Life Institute | Kornbluh R.,SRI International | Sommer-Larsen P.,Technical University of Denmark | Alici G.,University of Wollongong
Bioinspiration and Biomimetics | Year: 2011

Electroactive polymer (EAP) actuators are electrically responsive materials that have several characteristics in common with natural muscles. Thus, they are being studied as 'artificial muscles' for a variety of biomimetic motion applications. EAP materials are commonly classified into two major families: ionic EAPs, activated by an electrically induced transport of ions and/or solvent, and electronic EAPs, activated by electrostatic forces. Although several EAP materials and their properties have been known for many decades, they have found very limited applications. Such a trend has changed recently as a result of an effective synergy of at least three main factors: key scientific breakthroughs being achieved in some of the existing EAP technologies; unprecedented electromechanical properties being discovered in materials previously developed for different purposes; and higher concentration of efforts for industrial exploitation. As an outcome, after several years of basic research, today the EAP field is just starting to undergo transition from academia into commercialization, with significant investments from large companies. This paper presents a brief overview on the full range of EAP actuator types and the most significant areas of interest for applications. It is hoped that this overview can instruct the reader on how EAPs can enable bioinspired motion systems. © 2011 IOP Publishing Ltd.

Galantini F.,University of Pisa | Gallone G.,University of Pisa | Carpi F.,University of Pisa | Carpi F.,Technology and Life Institute
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2012

The main problem of dielectric elastomer (DE) actuators is today represented by the high driving electric fields (orders of 10-100 V/m) necessary for their activation. Although several attempts have been made in order to increase strains by enhancing the dielectric constant (ε') of such matrices and keeping low elastic moduli (Y) to control the ε/Y ratio, currently several challenges have still to be faced. In this work, a new approach is presented to enhance the electrical properties of DE elastomers. Soft elastomeric polyurethane (PU) matrices with foam structure were electrically modified via Corona process. Such matrices showed electret-like properties, possibly due to the presence of macro-dipoles established both at the matrix/pore surfaces and inside the bulk. Morphological (SEM, Bet), dielectric and dynamic-mechanical (DMA) analyses were performed in order to characterize the material. Results showed that Corona charging may represent a new promising route to obtain dielectric elastomers with improved dielectric properties, although ways to promote charge trapping and retention are still do be found. © 1994-2012 IEEE.

Vertechy R.,SantAnna School of Advanced Studies | Frisoli A.,SantAnna School of Advanced Studies | Bergamasco M.,SantAnna School of Advanced Studies | Carpi F.,Queen Mary, University of London | And 4 more authors.
Smart Materials and Structures | Year: 2012

Buckling dielectric elastomer actuators are a special type of electromechanical transducers that exploit electro-elastic instability phenomena to generate large out-of-plane axial-symmetric deformations of circular membranes made of non-conductive rubbery material. In this paper a simplified explicit analytical model and a general monolithic finite element model are described for the coupled electromechanical analysis and simulation of buckling dielectric elastomer membranes which undergo large electrically induced displacements. Experimental data are also reported which validate the developed models. © 2012 IOP Publishing Ltd.

Carpi F.,University of Pisa | Carpi F.,Technology and Life Institute | Frediani G.,University of Pisa | De Rossi D.,University of Pisa | De Rossi D.,Technology and Life Institute
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

Electrical control of optical focalisation is important in several fields, such as consumer electronics, medical diagnostics and optical communications. As an alternative to complex, bulky and expensive current solutions based on shifting constant-focus lenses, here we report on an electrically tunable lens made of dielectric elastomers as 'artificial muscle' materials. The device is inspired to the architecture of the crystalline lens and ciliary muscle of the human eye. A fluid-filled elastomeric lens is integrated with an annular elastomeric actuator that works as an artificial muscle. Electrical activation of the artificial muscle deforms the lens, with a relative variation of focal length comparable to that of the human lens. Optical performance is achieved with compact size, low weight, fast and silent operation, shock tolerance, no overheating, low power consumption, and inexpensive off-the-shelf materials. Results show that combing bio-inspired design with dielectric elastomer artificial muscles can open new perspectives on tunable optics. © 2012 Springer-Verlag.

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