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.

Fabrication of pH- and temperature-directed supramolecular materials from 1D fibers to exclusively 2D planar structures using an ionic self-assembly approach

Abstract: Constructing multiple-response smart materials is a very interesting and challenging task in materials science. Here we employed an ionic self-assembly (ISA) strategy to fabricate pH- and temperature-responsive supramolecular materials with controllable fluorescence emission properties by using charged Congo red (CR) and an oppositely charged COOH-functionalized imidazolium-based surface active ionic liquid (SAIL), N-decyl-N′-carboxymethyl imidazolium bromide ([N-C10, N′-COOH-Im]Br). One-dimensional (1D) slender fibers were obtained in aqueous solution at pH 3.2 by the self-assembly of CR/[N-C10, N′-COOH-Im]Br (molar ratio = 1 : 2) at room temperature. Noteworthy is that two-dimensional (2D) planar structures, viz. bamboo leaf-like, spindly, discoid and rectangular structures, were then formed only by further changing the pH of the solution. Of particular interest is that the transition between 1D and 2D structures is pH reversible. We also found that the slender fibers could aggregate into fiber bundle structures with increasing temperature. In addition, fluorescence emission of the obtained 1D and 2D materials can be controlled by adjusting the morphologies of the aggregates. The electrostatic and hydrophobic interactions, in concert with π–π stacking between Congo red and [N-C10, N′-COOH-Im]Br molecules, were regarded as the main driving forces. The dimer-type π–π stacking existing among CR molecules was testified by DFT calculations.

Multifunction fiber optic sensing system for smart applications

Abstract: The end of the twentieth century was witness to the merger of several technological disciplines that could eventually revolutionize engineering design philosophy and lead to the creation of intelligence within otherwise inanimate structures. This new technology will endow a structure with senses and the ability to react to its environment and change its state, shape and geometry. The key point for the practical realization of the so-called smart materials is the availability of robust and reliable structurally integrated sensors able to monitor the state of the structure. To this aim, a fiber optic multiparameter sensing system for process and structural health monitoring in concrete structures is presented. The reflectometric technique has been implemented for refractive-index measurements by using as transducer the fiber end/host interface. Results on the capability of the developed sensor to monitor the curing process of thermoset-based composites are presented. The integration with fiber Bragg gratings (FBGs) with the aim to perform temperature and strain measurements has been discussed. Two low-cost intensity-based demodulation techniques for FBGs interrogation have been developed and tested.

Fabrication of Moisture-Responsive Crystalline Smart Materials for Water Harvesting and Electricity Transduction.

Abstract: It is of profound significance with regard to the global energy crisis to develop new techniques and materials that can convert the chemical potential of water into other forms of energy, especially electricity. To address this challenge, we built a new type of energy transduction pathway (humidity gradients → mechanical work → electrical power) using moisture-responsive crystalline materials as the media for energy transduction. Single-crystal data revealed that a flexible zeolitic pyrimidine framework material, ZPF-2-Co, could undergo a reversible structural transformation (β to α phase) with a large unit cell change upon moisture stimulus. Dynamic water vapor sorption analysis showed a gate-opening effect with a steep uptake at as low as 10% relative humidity (RH). The scalable green synthesis approach and the fast water vapor adsorption-desorption kinetics made ZPF-2-Co an excellent sorbent to harvest water from arid air, as verified by real water-harvesting experiments. Furthermore, we created a gradient distribution strategy to fabricate polymer-hybridized mechanical actuators based on ZPF-2-Co that could perform reversible bending deformation upon a variation of the humidity gradient. This mechanical actuator showed remarkable durability and reusability. Finally, coupling the moisture-responsive actuator with a piezoelectric transducer further converted the mechanical work into electrical power. This work offers a new type of moisture-responsive smart material for energy transduction and provides an in-depth understanding of the responsive mechanism at the molecular level.

Phase change mediated mechanically transformative dynamic gel for intelligent control of versatile devices.

Abstract: Traditional devices, including conventional rigid electronics and machines, as well as emerging wearable electronics and soft robotics, almost all have a single mechanical state for particular service purposes. Nonetheless, dynamic materials with interchangeable mechanical states, which enable more diverse and versatile applications, are urgently necessary for intelligent and adaptive application cases in the future electronic and robot fields. Here, we report a gel-like material composed of a crosslinking polymer network impregnated with a phase changing molten liquid, which undergoes an exceptional stiffness transition in response to a thermal stimulus. Vice versa, the material switches from a soft gel state to a rigid solid state with a dramatic stiffness change of 105 times (601 MPa versus 4.5 kPa) benefiting from the liquid–solid phase change of the crystalline polymer once cooled. Such reversibility of the phase and mechanical transition upon thermal stimuli enables the dynamic gel mechanical transformation, demonstrating potential applications in an adhesive thermal interface gasket (TIG) to facilitate thermal transport, a high-temperature warning sensor and an intelligent gripper. Overall, this dynamic gel with a tunable stiffness change paves a new way to design and fabricate adaptive smart materials toward intelligent control of versatile devices.