A review of shape memory alloy research, applications and opportunities

Supramolecular materials, dynamic materials by nature, are defined as materials whose components are bridged via reversible connections and undergo spontaneous and continuous assembly/disassembly processes under specific conditions. On account of the dynamic and reversible nature of noncovalent interactions, supramolecular polymers have the ability to adapt to their environment and possess a wide range of intriguing properties, such as degradability, shape-memory, and self-healing, making them unique candidates for supramolecular materials. In this critical review, we address recent developments in supramolecular polymeric materials, which can respond to appropriate external stimuli at the fundamental level due to the existence of noncovalent interactions of the building blocks.

Stimuli-responsive supramolecular polymeric materials.

Shape-memory polymers and their composites: Stimulus methods and applications

Shape memory polymers are materials that can memorize temporary shapes and revert to their permanent shape upon exposure to an external stimulus such as heat, light, moisture or magnetic field. Such properties have enabled a variety of applications including deployable space structures, biomedical devices, adaptive optical devices, smart dry adhesives and fasteners. The ultimate potential for a shape memory polymer, however, is limited by the number of temporary shapes it can memorize in each shape memory cycle and the ability to tune the shape memory transition temperature(s) for the targeted applications. Currently known shape memory polymers are capable of memorizing one or two temporary shapes, corresponding to dual- and triple-shape memory effects (also counting the permanent shape), respectively. At the molecular level, the maximum number of temporary shapes a shape memory polymer can memorize correlates directly to the number of discrete reversible phase transitions (shape memory transitions) in the polymer. Intuitively, one might deduce that multi-shape memory effects are achievable simply by introducing additional reversible phase transitions. The task of synthesizing a polymer with more than two distinctive and strongly bonded reversible phases, however, is extremely challenging. Tuning shape memory effects, on the other hand, is often achieved through tailoring the shape memory transition temperatures, which requires alteration in the material composition. Here I show that the perfluorosulphonic acid ionomer (PFSA), which has only one broad reversible phase transition, exhibits dual-, triple-, and at least quadruple-shape memory effects, all highly tunable without any change to the material composition.

Tunable polymer multi-shape memory effect

Recent advances in shape–memory polymers: Structure, mechanism, functionality, modeling and applications

Shape-memory polymers (SMPs) have attracted significant attention from both industrial and academic researchers due to their useful and fascinating functionality. This review thoroughly examines progress in shape-memory polymers, including the very recent past, achieved by numerous groups around the world and our own research group. Considering all of the shape-memory polymers reviewed, we identify a classification scheme wherein nearly all SMPs may be associated with one of four classes in accordance with their shape fixing and recovering mechanisms and as dictated by macromolecular details. We discuss how the described shape-memory polymers show great potential for diverse applications, including in the medical arena, sensors, and actuators.

http://research.vuse.vanderbilt.edu/srdesign/2009/group8/Papers/shape%20memory%20polymers%20review%20article.pdf

Review of progress in shape-memory polymers

Accurate and reliable temperature measurement of many special inaccessible objects is a challenging task. Optical temperature sensing is a promising method to achieve it. The current status of optical thermometry of rare-earth ion doped phosphors is reviewed in detail. Based on the mechanisms of optical temperature sensing of different phosphors, temperature dependent luminescence spectra, the fluorescence intensity ratio technique in the data fitting process, and errors of the energy difference between thermally coupled levels, we describe the recent developments in the use of optical thermometry materials. The most important results obtained in each case are summarized, and the main challenges that we need to overcome are discussed. Research in the field of phosphor sensors has shown that they have significant advantages compared to conventional sensors in terms of their properties like greater sensitivity, freedom from electromagnetic interference, long path monitoring, and independence of compatibility with electronic devices.

/pdf/optical-temperature-sensing-of-rare-earth-ion-doped-gvd85epcl1.pdf

Optical temperature sensing of rare-earth ion doped phosphors

Based on first-principles density functional theory, we show that boron-doping significantly enhances the Li bond strength on the graphene. The transition from s–p hybridization of the Li-graphene complex to p–p hybridization of the Li-coated boron-doped graphene is responsible for the enhanced binding energy. The charge redistribution induced by boron-doping gives rise to two parts of an electrostatic potential energy (one is around the Li atom and the other is parallel to the graphene plane). Four polarized H2 molecules are attached to one Li atom with an optimal binding energy of ∼0.13 eV/H2.

Boron-tuned bonding mechanism of Li-graphene complex for reversible hydrogen storage

Improving the battery capacity usually induces a large volume expansion of the electrode, leading to poor reversibility and safety of the battery. Therefore, high specific capacity, fast charging rate, and good reversibility should be balanced in electrode materials. Using first-principles calculations, we systematically explore the InP3 monolayer as an anode material to hold Li (Na) atoms. The adsorption of Li (Na) induces the transformation of the sp2 hybridization of In to the sp3 hybridization, implying a strong binding and fast loading of Li (Na). Furthermore, the alkali-metal–InP3 system shows metallic characteristics which give rise to good electrical conductivity. In addition, Li (Na) diffusion in the zigzag direction is faster than that along the armchair direction. Especially, the Na diffusion barrier along the zigzag direction is as low as 0.06 eV, corresponding to ultrafast charge/discharge capability. Balancing the stability and storage capacity, the specific capacity and average electrode potential of Li (Na) are 258.1 (258.1) mA h g−1 and 0.53 (1.49) V, respectively. Finally, the structure of InP3 is well maintained upon the adsorption of Li (Na) even at the maximum concentration, suggesting its good stability and reversibility. The above-mentioned excellent properties suggest that the InP3 monolayer is a promising anode material for alkali-metal batteries.

Chun-Sheng Liu

Papers

Review of progress in shape-memory polymers

Optical temperature sensing of rare-earth ion doped phosphors

Boron-tuned bonding mechanism of Li-graphene complex for reversible hydrogen storage

Monolayer InP3 as a reversible anode material for ultrafast charging lithium- and sodium-ion batteries: a theoretical study

Arsenene as a promising candidate for NO and NO 2 sensor: A first-principles study