Papers by paola nardinocchi
Journal of Biomechanics, 2006
Oral Presentations increases (i.e. mechanical anisotropy decreases). To demonstrate its capabilit... more Oral Presentations increases (i.e. mechanical anisotropy decreases). To demonstrate its capabilities, the model is first applied to study remodeling of the fiber architecture in a biaxially loaded cube. The model is then employed to investigate collagen remodeling in the arterial wall and aortic valve. In addition, the feasibility of using strain and stress based remodeling laws can be addressed with the proposed algorithm.
Procedia IUTAM, 2015
Bio-hybrid system are morphing structures whose shaping can be electrically driven and strongly d... more Bio-hybrid system are morphing structures whose shaping can be electrically driven and strongly depends on the geometrical and mechanical characteristics of the system. The estimation of those characteristics which allow for getting target shapes is a great challenge. We present and discuss an approximate model for narrow bio-hybrid strips which works well in plane bending. A generalization towards three-layers bio-hybrid system is presented.
Proceedings. Mathematical, physical, and engineering sciences / the Royal Society, Jan 8, 2014
We describe swelling-driven curving in originally straight and non-homogeneous beams. We present ... more We describe swelling-driven curving in originally straight and non-homogeneous beams. We present and verify a structural model of swollen beams, based on a new point of view adopted to describe swelling-induced deformation processes in bilayered gel beams, that is based on the split of the swelling-induced deformation of the beam at equilibrium into two components, both depending on the elastic properties of the gel. The method allows us to: (i) determine beam stretching and curving, once assigned the characteristics of the solvent bath and of the non-homogeneous beam, and (ii) estimate the characteristics of non-homogeneous flat gel beams in such a way as to obtain, under free-swelling conditions, three-dimensional shapes. The study was pursued by means of analytical, semi-analytical and numerical tools; excellent agreement of the outcomes of the different techniques was found, thus confirming the strength of the method.
Journal of Intelligent Material Systems and Structures, 2011
The modeling of the complex response of the IPMC-like body to electrical and mechanical stimuli i... more The modeling of the complex response of the IPMC-like body to electrical and mechanical stimuli is set within the context of the 3-D theory of linear elasticity. A field of chemically induced distortions is included in the model; these mechanical distortions and the derivation of the final PDE equations of the multiphysics problem are thermodynamically consistent. Some results of the numerical experiments are revisited through an original analysis of the stress distribution along the IPMC-like body.
Soft Matter, 2015
Understanding and controlling the shape of thin, soft objects has been the focus of significant r... more Understanding and controlling the shape of thin, soft objects has been the focus of significant research efforts among physicists, biologists, and engineers in the last decade. These studies aim to utilize advanced materials in novel, adaptive ways such as fabricating smart actuators or mimicking living tissues. Here, we present the controlled growth-like morphing of 2D sheets into 3D shapes by introducing a new class of geometric composite structures that deform by residual swelling. The morphing of these geometric composites is dictated by both swelling and geometry, with diffusion controlling the swelling-induced actuation, and geometric confinement dictating the structure's deformed shape. Building on a simple mechanical analog, we develop an analytical model that quantitatively describes how the Gaussian and mean curvatures of a thin disk are affected by the interplay among geometry, mechanics, and swelling. This model is in excellent agreement with our experiments and numerics. We show that the dynamics of residual swelling is dictated by a competition between two characteristic diffusive length scales governed by geometry. Our results provide the first 2D analog of Timoshenko's classical formula for the thermal bending of bimetallic beams -our generalization explains how the Gaussian curvature of a 2D geometric composite is affected by geometry and elasticity. The understanding conferred by these results suggests that the controlled shaping of geometric composites may provide a simple complement to traditional manufacturing techniques.
Journal of Applied Physics, 2013
ABSTRACT The curled actuated shapes of ionic polymer metal composites (IPMCs) are described withi... more ABSTRACT The curled actuated shapes of ionic polymer metal composites (IPMCs) are described within a nonlinear physics-based model of IPMC actuators. A key characteristic of the model is the refined, even if black box based, modeling of the relative permittivity of the IPMCs which strongly influences the actuation performances of the IPMC, when voltages higher than 1 V are involved. A varying-along-the-thickness relative permittivity is proposed to take into account the highly heterogeneous layers resulting from electrode deposition, where a charge redistribution occurs. Moreover, the presence of the metal electrodes has been considered as hampering the IPMCs' bending deformations, so reducing the actuation performances of the IPMC. A series of numerical tests have been planned and discussed to show the characteristics of the model; in particular, the model is shown to be strong enough to catch the not monotonic behavior of IPMCs, when back relaxation is manifested.
PLoS ONE, 2014
The aim of this study is to investigate human left ventricular heart morphological changes in tim... more The aim of this study is to investigate human left ventricular heart morphological changes in time among 17 healthy subjects. Preliminarily, 2 patients with volumetric overload due to aortic insufficiency were added to our analyses. We propose a special strategy to compare the shape, orientation and size of cardiac cycle's morphological trajectories in time. We used 3D data obtained by Speckle Tracking Echocardiography in order to detect semi-automated and homologous landmarks clouds as proxies of left ventricular heart morphology. An extended Geometric Morphometrics toolkit in order to distinguish between intra-and inter-individual shape variations was used. Shape of trajectories with inter-individual variation were compared under the assumption that trajectories attributes, estimated at electrophysiologically homologous times are expressions of left ventricular heart function. We found that shape analysis as commonly applied in Geometric Morphometrics studies fails in identifying a proper morpho-space to compare the shape of morphological trajectories in time. To overcome this problem, we performed a special type of Riemannian Parallel Transport, called ''linear shift''. Whereas the two patients with aortic insufficiency were not differentiated in the static shape analysis from the healthy subjects, they set apart significantly in the analyses of motion trajectory's shape and orientation. We found that in healthy subjects, the variations due to inter-individual morphological differences were not related to shape and orientation of morphological trajectories. Principal Component Analysis showed that volumetric contraction, torsion and twist are differently distributed on different axes. Moreover, global shape change appeared to be more correlated with endocardial shape change than with the epicardial one. Finally, the total shape variation occurring among different subjects was significantly larger than that observable across properly defined morphological trajectories.
Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences
We describe swelling-driven curving in originally straight and non-homogeneous beams. We present ... more We describe swelling-driven curving in originally straight and non-homogeneous beams. We present and verify a structural model of swollen beams, based on a new point of view adopted to describe swelling-induced deformation processes in bilayered gel beams, that is based on the split of the swelling-induced deformation of the beam at equilibrium into two components, both depending on the elastic properties of the gel. The method allows us to: (i) determine beam stretching and curving, once assigned the characteristics of the solvent bath and of the non-homogeneous beam, and (ii) estimate the characteristics of non-homogeneous flat gel beams in such a way as to obtain, under free-swelling conditions, three-dimensional shapes. The study was pursued by means of analytical, semi-analytical and numerical tools; excellent agreement of the outcomes of the different techniques was found, thus confirming the strength of the method.
Proceedings of SPIE - The International Society for Optical Engineering
In the last decade, ionic polymer–metal composites are emerged as viable intelligent materials wo... more In the last decade, ionic polymer–metal composites are emerged as viable intelligent materials working both as bending actuators and energy harvesting systems. Recently, the feasibility of actuation from mechanical buckling has been investigated. In the present research, we present relevant numerical experiments concerning the possible electromechanical transduction when different patterned electrodes are considered. The focus of this research is theoretical, numerical, and experimental. In particular, with reference to almost one–dimensional IPMC strips, we take into account the large influence of electrodes’ bending stiffness on the IPMC behavior. We consider an original continuous metal strip covering the ionic polymer, and the patterned electrodes with one or more gaps. The actuation response of the system to low and to high voltages is studied; a strong difference is evidenced in the two situations as, in presence of high voltage, the system shows a buckling in opposite directi...
International Journal of Non-Linear Mechanics
A thermodynamically consistent modeling of the non-linear multiphysics behavior of ionic polymers... more A thermodynamically consistent modeling of the non-linear multiphysics behavior of ionic polymers is presented and discussed. A key ingredient of the model is the treatment of the electrically induced deformations, resulting in a large bending motion when ionic polymers are employed in IPMCs (Ionic Polymer-Metal Composites). With specific reference to the mechanics, the position of the linear models for ionic polymers is discussed and set within a formalized linearization procedure. A set of numerical experiments is developed, showing the capability of the model to capture the fundamental features of the actuation mechanism.
A joint preliminary study has been performed to elucidate the capability of IPMC-based structures... more A joint preliminary study has been performed to elucidate the capability of IPMC-based structures mimicking the behavior of biological systems. The structural deformation in response to an applied voltage is described within a nonlinear physics-based model of IPMC actuators. A characteristic of the model is the varying-along-the-thickness relative permittivity of the IPMCs, which takes into account the highly heterogeneous layers resulting from electrode deposition, where charge redistribution occurs. Preliminary experiments on an IPMC-based medusoid are presented to offer some validation of the modeling approach and provide directions for further studies.
Lecture Notes in Applied and Computational Mechanics, 2010
ABSTRACT Active Fiber-reinforced Composites are artificial bodies consisting of one or more layer... more ABSTRACT Active Fiber-reinforced Composites are artificial bodies consisting of one or more layers of parallel ceramic fibers embedded in a polymer matrix. In this paper we propose a mathematical model for their constitutive response by importing certain concepts from the modeling of fibrous living tissues and by regarding an AFC as a special piezoelectric material body whose stored energy is a weighted sum of the stored energies of fibers and matrix.
Procedia IUTAM, 2015
Bio-hybrid system are morphing structures whose shaping can be electrically driven and strongly d... more Bio-hybrid system are morphing structures whose shaping can be electrically driven and strongly depends on the geometrical and mechanical characteristics of the system. The estimation of those characteristics which allow for getting target shapes is a great challenge. We present and discuss an approximate model for narrow bio-hybrid strips which works well in plane bending. A generalization towards three-layers bio-hybrid system is presented.
International Journal of Solids and Structures, 2012
ABSTRACT The purpose of the paper is to present a class of reduced models borrowed from structura... more ABSTRACT The purpose of the paper is to present a class of reduced models borrowed from structural mechanics aimed at specifically describing swelling-induced bending deformations in a gel bar. A distinct bending pattern to be confirmed by an appropriate experimental setup is evidenced through the analysis of a plane stress–diffusion model. Moreover, a further reduced 1D stress–diffusion model driven by an integro-differential equation is derived. In particular, it is shown that there exists a range of the material parameters where the standard 1D diffusion equation holds.
International Journal of Non-Linear Mechanics, 2013
ABSTRACT A thermodynamically consistent modeling of the non-linear multiphysics behavior of ionic... more ABSTRACT A thermodynamically consistent modeling of the non-linear multiphysics behavior of ionic polymers is presented and discussed. A key ingredient of the model is the treatment of the electrically induced deformations, resulting in a large bending motion when ionic polymers are employed in IPMCs (Ionic Polymer-Metal Composites). With specific reference to the mechanics, the position of the linear models for ionic polymers is discussed and set within a formalized linearization procedure. A set of numerical experiments is developed, showing the capability of the model to capture the fundamental features of the actuation mechanism.
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Papers by paola nardinocchi