Smart material

About: Smart material is a research topic. Over the lifetime, 3704 publications have been published within this topic receiving 74280 citations. The topic is also known as: intelligent material & responsive material.

Programmable Liquid Matter: 2D Shape Deformation of Highly Conductive Liquid Metals in a Dynamic Electric Field

Abstract: In this paper, we demonstrate a method for the dynamic 2D transformation of liquid matter and present unique organic animations based on spatio-temporally controlled electric fields. In particular, we deploy a droplet of liquid metal (Gallium indium eutectic alloy) in a 7x7 electrode array prototype system, featuring an integrated image tracking system and a simple GUI. Exploiting the strong dependance of EGaIn's surface tension on external electric voltages, we control multiple electrodes dynamically to manipulate the liquid metal into a fine-grained desired shape. Taking advantage of the high conductivity of liquid metals, we introduce a shape changing, reconfigurable smart circuit as an example of unique applications. We discuss system constraints and the overarching challenge of controlling liquid metals in the presence of phenomena such as splitting, self-electrode interference and finger instabilities. Finally, we reflect on the broader vision of this project and discuss our work in the context of the wider scope of programmable materials.

Through-the-thickness mechanical properties of smart quasi-isotropic carbon/epoxy laminates

Abstract: Integrating smart materials such as fibre optic sensors or actuating shape memory alloy (SMA) wires with the host composites during manufacturing is one of the most fundamental aspects in the technology of smart structures. Sensing or actuating needs often dictate at what depth and how many sensors or wires should be embedded in the host composites. Thus manufacturing defects like resin pockets or poor interfacial bonding occur and could affect interlaminar shear (ILS) and flexural mechanical behaviour of smart composite structures. Limited information on these through-the-thickness mechanical properties is available from smart quasi-isotropic (QI) laminates of less than 8-ply thick, but no such data exists for thicker smart QI laminates. Therefore in the present research, both ILS and flexural mechanical properties of smart QI carbon/epoxy beams have been determined by using short beam shear (SBS) and Iosipescu methods as well as three-point and four-point bending methods. While SMA wires were embedded at selected interfaces of two different lay-ups in the longitudinal direction, optical fibres (OFs) were embedded at six different ply interfaces in both the longitudinal and transverse directions. It was found that neither ILS properties nor flexural modulus was affected, irrespective of the smart materials, their orientation, or through-the-thickness location. The flexural strengths did not suffer any noticeable degradation when the OFs or SMA wires were embedded either in the longitudinal direction or in the transverse direction in the tensile region. It was shown that the flexural strength degraded significantly when the OFs embedded in the transverse direction were in the compressive region.

Comments on the physical basis of the active materials concept

Abstract: During the last decade constant improvements have been made in materials and structures design and control. But now some performance objectives cannot be achieved using classical technologies and require the use of the smart materials concept. But it is at the actuation end of the equation that smart materials and structures present the greatest challenge. It is here in particular that improved and even new materials have a leading role to play. Piezoelectrics, electrostrictives, photostrictives, magnetostrictives, electroactive polymers, shape memory materials, carbon nanotubes, rheological fluids,...all have their important contributions to make. So this paper aims to perform a brief review of the physical basis of the active materials behaviour.

Characterization and Variational Modeling of Ionic Polymer Transducers

Abstract: Ionomeric polymers are a promising class of intelligent material which exhibit electromechanical coupling similar to that of piezoelectric bimorphs. ionomeric polymers are much more compliant than piezoelectric ceramics or polymers and have been shown to produce actuation strain on the order of 2% at operating voltages between 1 V and 3 V (Akle et al., 2004, Proceedings IMECE). Their high compliance is advantageous in low force sensing configurations because ionic polymers have a very little impact on the dynamics of the measured system. Here we present a variational approach to the dynamic modeling of structures which incorporate ionic polymer materials. To demonstrate the method a cantilever beam model is developed using this variational approach. The modeling approach requires a priori knowledge of three empirically determined material properties: elastic modulus, dielectric permittivity, and effective strain coefficient. Previous work by Newbury and Leo has demonstrated that these three parameters are strongly frequency dependent in the range between less than 1 Hz to frequencies greater than 1 kHz. Combining the frequency-dependent material parameters with the variational method produces a second-order matrix representation of the structure. The frequency dependence of the material parameters is incorporated using a complex-property approach similar to the techniques for modeling viscoelastic materials. A transducer is manufactured and the method of material characterization is applied to determine the mtaerial properties. Additional experiments are performed on this transducer and both the material and structural model are validated. Finally, the model is shown to predict sensing response very well in comparison to experimental results, which supports the use of an energy-based variational approach for modeling ionomeric polymer transducers.

Mechanochromic Reconfigurable Metasurfaces.

Abstract: The change of optical properties that some usually natural compounds or polymeric materials show upon the application of external stress is named mechanochromism. Herein, an artificial nanomechanical metasurface formed by a subwavelength nanowire array made of molybdenum disulfide, molybdenum oxide, and silicon nitride changes color upon mechanical deformation. The aforementioned deformation induces reversible changes in the optical transmission (relative transmission change of 197% at 654 nm), thus demonstrating a giant mechanochromic effect. Moreover, these types of metasurfaces can exist in two nonvolatile states presenting a difference in optical transmission of 45% at 678 nm, when they are forced to bend rapidly. The wide optical tunability that photonic nanomechanical metasurfaces, such as the one presented here, possess by design, can provide a valuable platform for mechanochromic and bistable responses across the visible and near infrared regime and form a new family of smart materials with applications in reconfigurable, multifunctional photonic filters, switches, and stress sensors.