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The cochlea is a spiral-shaped, liquid-filled organ in the inner ear that converts sound with high frequency selectivity over a wide pressure range to neurological signals that are eventually interpreted by the brain. The cochlear partition, consisting of the organ of Corti supported below by the basilar membrane and attached above to the tectorial membrane, plays a major role in the frequency analysis. In early fluid-structure interaction models of the cochlea, the mechanics of the cochlear partition were approximated by a series of single-degree-of-freedom systems representing the distributed stiffness and mass of the basilar membrane. Recent experiments suggest that the mechanical properties of the tectorial membrane may also be important for the cochlea frequency response and that separate waves may propagate along the basilar and tectorial membranes. Therefore, a two-dimensional two-compartment finite difference model of the cochlea was developed to investigate the independent coupling of the basilar and tectorial membranes to the surrounding liquid. Responses are presented for models using two- or three-degree-of-freedom stiffness, damping, and mass parameters derived from a physiologically based finite element model of the cochlear partition. Effects of changes in membrane and organ of Corti stiffnesses on the individual membrane responses are investigated. [ABSTRACT FROM AUTHOR]

This paper demonstrates the feasibility of shape memory polymer (SMP) activation by medium-infrared laser light. Medium-infrared light is transmitted by an optical fiber embedded in the SMP matrix, and the shape recovery process and temperature distribution are recorded by an infrared camera. Light-induced SMP exhibits potential applications in biomedicines and flexible displays. [ABSTRACT FROM AUTHOR]

The present work studies the synergistic effect of carbon nanofiber (CNF) and carbon nanopaper on the shape recovery of shape memory polymer (SMP) composite. The combination of CNF and carbon nanopaper was used to improve the thermal and electrical conductivities of the SMP composite. The carbon nanopaper was coated on the surface of the SMP composite in order to achieve the actuation by electrical resistive heating. CNFs were blended with the SMP resin to improve the thermal conductivity to facilitate the heat transfer from the nanopaper to the underlying SMP composite to accelerate the electroactive responses. [ABSTRACT FROM AUTHOR]

Electromechanical instability may occur in dielectric elastomer films due to the coupling between mechanical forces and electric fields. According to Zhao and Suo [Appl. Phys. Lett. 91, 061921 (2007)], free-energy in any form, which consists of elastic strain energy and electric energy, can be used to analyze the electromechanical stability of dielectric elastomer. By taking the permittivity as a variable depending on the deformation in a free energy function, a relationship is established among critical nominal electric field, critical real electric field, nominal stress, and principal stretch ratios. The accurate expressions of these parameters are presented for a special equal biaxial stretch case. All the results obtained by utilizing the single material constant neo-Hookean elastic strain energy model coincide with the conclusions by Zhao and Suo. [ABSTRACT FROM AUTHOR]

We would like to thank Díaz-Calleja et al. [Appl. Phys. Lett. 93, 101902 (2008)] for their insight and help on “On electromechanical stability of dielectric elastomers;” unstable domain of electromechanical coupling system of neo-Hookean-type silicone was analyzed by Díaz-Calleja et al. Different from that given in the paper of Díaz-Calleja, in the current work, the elastic strain energy function with two material constants was used to analyze the stable domain of electromechanical coupling system of Mooney–Rivlin-type silicone, and the results seem to support the theory of Díaz-Calleja. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Water-driven Programmable Polyurethane Shape Memory Polymer: Demonstrate and Mechanism," by W. M. Huang in the previous issue.

We would like to thank Zhao and Suo [Appl. Phys. Lett. 91, 061921 (2007)] for their insights and help on “Method to analyze electromechanical stability of dielectric elastomers;” Suo provided the theory of stability of dielectric elastomers. In this Comment, the nonlinear electromechanical theory for deformable dielectrics described in Suo’s paper is applied to analyze the stability of dielectric elastomers. Different from that given in Suo’s paper, in the current work, elastic strain energy functional with two material constants is used for the stability analysis. Dielectric materials with different values of k are analyzed, and the results seem to support Suo’s theory. These results can be applied in the design of dielectric elastomer actuator and in larger application spectrum. [ABSTRACT FROM AUTHOR]

A correction to the article "Water-driven programmable polyurethane shape memory polymer: Demonstration and mechanism" that was published online on August 2, 2010 is presented.