Showing papers on "Smart material published in 2019"

Design and Applications of Photoresponsive Hydrogels.

Abstract: Hydrogels are the most relevant biochemical scaffold due to their tunable properties, inherent biocompatibility, and similarity with tissue and cell environments. Over the past decade, hydrogels have developed from static materials to "smart" responsive materials adapting to various stimuli, such as pH, temperature, chemical, electrical, or light. Light stimulation is particularly interesting for many applications because of the capability of contact-free remote manipulation of biomaterial properties and inherent spatial and temporal control. Moreover, light can be finely adjusted in its intrinsic properties, such as wavelength and intensity (i.e., the energy of an individual photon as well as the number of photons over time). Water is almost transparent for light in the photochemically relevant range (NIR-UV), thus hydrogels are well-suited scaffolds for light-responsive functionality. Hydrogels' chemical and physical variety combined with light responsiveness makes photoresponsive hydrogels ideal candidates for applications in several fields, ranging from biomaterials, medicine to soft robotics. Herein, the progress and new developments in the field of light-responsive hydrogels are elaborated by first introducing the relevant photochemistries before discussing selected applications in detail.

Developments in 4D-printing: a review on current smart materials, technologies, and applications

Abstract: Recent advances in additive manufacturing (AM), commonly known as three-dimensional (3D)-printing, have allowed researchers to create complex shapes previously impossible using traditional fabricat...

X-ray and UV Dual Photochromism, Thermochromism, Electrochromism, and Amine-Selective Chemochromism in an Anderson-like Zn7 Cluster-Based 7-Fold Interpenetrated Framework

Abstract: Smart materials are highly desirable over the recent decade due to the growing demand of complicated nature. Stable stimuli-responsive smart materials exhibit widespread potential for applications in smart windows, sensors, separators, chemical valves, and release platforms but are rare. Despite being good candidates, viologen-based multifunctional smart materials are still a challenging task for chemists. To obtain such materials, the judicious strategy is to introduce polynuclear metal-carboxylate clusters as electron donors into a stable framework to increase chromic sensitivity. Toward this endeavor, we have synthesized a novel viologen-based polymer with a unique Anderson-like metal-carboxylate cluster, [Zn7(bpybc)3(o-BDC)6]·2NO3·6H2O (bpybc = 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium, o-BDC = o-benzenedicarboylic acid) (1), which is a particular 7-fold interpenetrated framework with a 3D pcu network in which bpybc ligand as the linker and Zn7O30C12 as the second building unit (Zn7 SBU) were used as 6-connected nodes. More importantly, it shows excellent chromic behavior in response to multiple external stimuli especially soft X-ray and UV dual light, temperature, electricity, and organic amines, which stand out in the viologen-based polymers. Interestingly, the coloration process of 1 from "core" to "edge" is observed upon heating at the appropriate temperature, which has not yet been found in other reported thermochromic materials. Of particular interest for 1 is the couple of quaternary stimuli-sensitive abilities because it simultaneously meets the following conditions: (i) the capability of withstanding high light, higher temperature, extreme pH, and other harsh conditions; and (ii) the high sensitivity to external stimuli keeping away from photodegradation, thermal relaxation, side reactions, and so on. To be noted, 1 has high thermal stability and chemical stability, which are excellent advantages as smart materials. To further develop possible practical utilization, 1 has been doped into the polymer matrixes to construct a hybrid film, which not only keeps the response to external stimuli but also significantly improves the repeatability of the photochromic process, indicating that a new smart device with multi-stimuli-responsive functions will emerge successively in the future.

Artificial phototropism for omnidirectional tracking and harvesting of light.

Abstract: Many living organisms track light sources and halt their movement when alignment is achieved. This phenomenon, known as phototropism, occurs, for example, when plants self-orient to face the sun throughout the day. Although many artificial smart materials exhibit non-directional, nastic behaviour in response to an external stimulus, no synthetic material can intrinsically detect and accurately track the direction of the stimulus, that is, exhibit tropistic behaviour. Here we report an artificial phototropic system based on nanostructured stimuli-responsive polymers that can aim and align to the incident light direction in the three-dimensions over a broad temperature range. Such adaptive reconfiguration is realized through a built-in feedback loop rooted in the photothermal and mechanical properties of the material. This system is termed a sunflower-like biomimetic omnidirectional tracker (SunBOT). We show that an array of SunBOTs can, in principle, be used in solar vapour generation devices, as it achieves up to a 400% solar energy-harvesting enhancement over non-tropistic materials at oblique illumination angles. The principle behind our SunBOTs is universal and can be extended to many responsive materials and a broad range of stimuli.

Magnetic programming of 4D printed shape memory composite structures

Abstract: 4D printed shape memory polymers and their composites are currently a highly topical research area. The potential applications for 4D printed smart materials are wide-reaching, with particular promise for personalized medicine. In this work, we 4D printed various structures made of biocompatible and biodegradable polylactic acid (PLA) and PLA/Fe3O4 composite filaments. The shape memory behaviors of the 4D printed structures triggered by magnetic field were investigated. The printed structures can return to their original shapes with a high speed in just a few seconds. Moreover, the structures like bone tissues printed by PLA/Fe3O4 composites filaments with 15% Fe3O4 were actuated by magnetic field at 27.5 kHz. During the shape recovery process, surface temperature of the printed structures is uniform and around 40 °C. This physiologically relevant operating temperature range is a highly attractive feature for potential healthcare and biomedical applications.

Smart materials in additive manufacturing: state of the art and trends

Abstract: Additive Manufacturing or 3D Printing has a great potential to develop significant advances in materials, printers’ technology, and processes. Thus, the layer by layer manufacturing has existed for...

Wettability of graphene: from influencing factors and reversible conversions to potential applications

Abstract: As a member of the carbon material family, graphene has long been the focus of research on account of its abundant excellent properties. Nevertheless, many previous research works have attached much importance to its mechanical capacity and electrical properties, and not to its surface wetting properties with respect to water. In this review, a series of methods are put forward for characterization of the water contact angle of graphene, such as experimental measurements, classic molecular dynamics simulations, and formula calculations. A series of factors that affect the wettability of graphene, including defects, controllable atmosphere, doping, and electric field, are also discussed in detail, and have rarely have been covered in other review articles before. Finally, with the developments of smart surfaces, a reversible wettability variation of graphene from hydrophobic to hydrophilic is important in the presence of external stimulation and is discussed in detail herein. It is anticipated that graphene could serve as a tunable wettability coating for further developments in electronic devices and brings a new perspective to the construction of smart material surfaces.

Dual-3D Femtosecond Laser Nanofabrication Enables Dynamic Actuation

Abstract: Strategies that can make general materials smart are highly desired for developing artificial shape-morphing systems and devices. However, at present, it still lacks universal technologies that enable designable prototyping of deformable 3D micro-nanostructures. Inspired by natural automation systems, for instance, tendrils, leaves, and flowers deform dynamically under external stimuli by varying internal turgor, we report a dual-3D femtosecond laser processing strategy for fabricating smart and deformable 3D microactuators based on general photopolymers. By programming the size and distributions of voxels at the nanoscale, both the 3D profile and the 3D internetwork of a general photopolymer could be tailored in a controlled manner; thus, 3D microstructures encoded with precisely tailored networks could perform predictable deformations under certain stimuli. Using this dual-3D fabrication approach, energetic 3D microactuators, including a smart microflower, a responsive microvale, and an eight-finger microclaw, that permit controllable manipulation have been successfully developed.

Review of Polymeric Materials in 4D Printing Biomedical Applications.

Abstract: The purpose of 4D printing is to embed a product design into a deformable smart material using a traditional 3D printer. The 3D printed object can be assembled or transformed into intended designs by applying certain conditions or forms of stimulation such as temperature, pressure, humidity, pH, wind, or light. Simply put, 4D printing is a continuum of 3D printing technology that is now able to print objects which change over time. In previous studies, many smart materials were shown to have 4D printing characteristics. In this paper, we specifically review the current application, respective activation methods, characteristics, and future prospects of various polymeric materials in 4D printing, which are expected to contribute to the development of 4D printing polymeric materials and technology.

Recent Advances on Stimuli‐Responsive Smart Materials and their Applications

Abstract: Stimuli-responsive materials have raised major attention in digital technology, sensors and biomedical applications owing to quick response towards external stimuli, for example light, voltage, pressure, temperature, mechanical friction and pH. Nevertheless, action of external stimuli on organic materials affects their internal physico-chemical properties and facilitates improved thermal/photo stability, tuning detection sensitivity, accuracy and biocompatibility. This review article highlights recent progress on stimuli-responsive materials with mixed valence species, viologens, twisting chirality, crystalline/amorphous, sol-gel phase transitions and resulting supramolecular nanostructures via non-covalent interactions. These materials can be applied in flexible electronics, drug delivery, detection of pollutants and bioimaging. Thus, the demand for widespread research on development of stimuli-responsive materials are requisite to resolve the challenges pertaining to stability and sensitivity of devices for design in comprehensive technology.

A novel flexible phase change composite with electro-driven shape memory, energy conversion/storage and motion sensing properties

Abstract: In addition to their lower thermal conductivity, leakage during the melting phase and poor energy conversion ability, the fragility of phase change materials is an issue that is worth addressing to widen their application scope. Herein, we propose a low-cost and facile method to develop a flexible electro-driven phase change composite with unidirectional shape memory effects and motion detection properties. The phase change composite is composed of carbonized cotton cloth as a conductive supporting structure, paraffin wax as a latent heat storage material and thermoplastic polyurethane as a protective layer. The woven framework of carbonized cloth endowed the paraffin wax with the ability to generate Joule heating at a lower voltage due to its high electrical conductivity (374 S m−1). The multifunctional layer of thermoplastic polyurethane wrapped the carbon cloth/paraffin and greatly improved the form-stability, flexibility and mechanical strength of the composite. Shape fixity and shape recovery properties of the composite were achieved by the synergic effect of the phase transition in paraffin and the elasticity of thermoplastic polyurethane. Moreover, the presence of conductive carbon cloth enabled the composite to achieve good electrothermal conversion efficiency and motion sensing properties. The fabricated flexible phase change composite may serve as a smart material for versatile thermal management applications.

Photomechanical Organic Crystals as Smart Materials for Advanced Applications.

Abstract: Photomechanical molecular crystals are receiving much attention due to their efficient conversion of light into mechanical work and advantages including faster response time; higher Young's modulus; and ordered structure, as measured by single-crystal X-ray diffraction. Recently, various photomechanical crystals with different motions (contraction, expansion, bending, fragmentation, hopping, curling, and twisting) are appearing at the forefront of smart materials research. The photomechanical motions of these single crystals during irradiation are triggered by solid-state photochemical reactions and accompanied by phase transformation. This Minireview summarizes recent developments in growing research into photoresponsive molecular crystals. The basic mechanisms of different kinds of photomechanical materials are described in detail; recent advances in photomechanical crystals for promising applications as smart materials are also highlighted.

pH and Thermo Dual-Responsive Fluorescent Hydrogel Actuator.

Abstract: As one of the most important smart materials, fluorescent hydrogel actuators can produce both color and shape changes under external stimuli. In the present work, an effective approach to develop a novel fluorescent hydrogel actuator with pH and thermo dual responsiveness is proposed. Through incorporating pH-responsive perylene tetracarboxylic acid (PTCA), which is a typical fluorescent moiety with aggregation-caused quenching (ACQ) effect, into an anisotropic poly(N-isopropylacrylamide)-polyacrylamide (PNIPAm-PAAm) structure, the obtained hydrogel exhibits stable thermoresponsive shape deformation and switchable fluorescence performance upon a pH trigger. Therefore, fluorescence-quenching-based and actuation-based information can be revealed when exposed to UV light and immersed into warm water, respectively. Moreover, the thermoresponsive actuating behavior can be applied to further hide the fluorescence-quenching-based images. The present work may provide new insights into the design and preparation of novel stimuli-responsive hydrogel actuators.

Voxelated Molecular Patterning in Three-Dimensional Freeforms

Abstract: The ability to pattern material response, voxel by voxel, to direct actuation and manipulation in macroscopic structures can enable devices that utilize ambient stimuli to produce functional respon...

Actuator Materials: Review on Recent Advances and Future Outlook for Smart Textiles

Abstract: Smart textiles based on actuator materials are of practical interest, but few types have been commercially exploited. The challenge for researchers has been to bring the concept out of the laboratory by working out how to build these smart materials on an industrial scale and permanently incorporate them into textiles. Smart textiles are considered as the next frontline for electronics. Recent developments in advance technologies have led to the appearance of wearable electronics by fabricating, miniaturizing and embedding flexible conductive materials into textiles. The combination of textiles and smart materials have contributed to the development of new capabilities in fabrics with the potential to change how athletes, patients, soldiers, first responders, and everyday consumers interact with their clothes and other textile products. Actuating textiles in particular, have the potential to provide a breakthrough to the area of smart textiles in many ways. The incorporation of actuating materials in to textiles is a striking approach as a small change in material anisotropy properties can be converted into significant performance enhancements, due to the densely interconnected structures. Herein, the most recent advances in smart materials based on actuating textiles are reviewed. The use of novel emerging twisted synthetic yarns, conducting polymers, hybrid carbon nanotube and spandex yarn actuators, as well as most of the cutting–edge polymeric actuators which are deployed as smart textiles are discussed.

Smart polymers for cell therapy and precision medicine

Abstract: Soft materials have been developed very rapidly in the biomedical field over the past 10 years because of advances in medical devices, cell therapy, and 3D printing for precision medicine. Smart polymers are one category of soft materials that respond to environmental changes. One typical example is the thermally-responsive polymers, which are widely used as cell carriers and in 3D printing. Self-healing polymers are one type of smart polymers that have the capacity to recover the structure after repeated damages and are often injectable through needles. Shape memory polymers are another type with the ability to memorize their original shape. These smart polymers can be used as cell/drug/protein carriers. Their injectability and shape memory performance allow them to be applied in bioprinting, minimally invasive surgery, and precision medicine. This review will describe the general materials design, characterization, as well as the current progresses and challenges of these smart polymers.

Multifunctional Superwettable Material with Smart pH Responsiveness for Efficient and Controllable Oil/Water Separation and Emulsified Wastewater Purification.

Abstract: Developing multifunctional superwettable materials is highly demanded in the oil/water separation field but remains challenging due to the critical limitations of complex fabrication strategy and high cost. Herein, based on the cost-effective kaolin nanoparticles, we present a convenient and mild strategy for fabricating a smart superwettable material with multiple excellent performances, such as pH-responsive water wettability, self-cleaning property, favorable buoyancy, and air purification performance. By virtue of the dual rough surface structure and special chemical composition, the resultant material surface exhibits a superior pH-dependent wettability, which can be reversibly switched between superamphiphobicity and superhydrophilicity-superoleophobicity for many times in accordance with the pH value of the corresponding aqueous solution. As a result, the obtained superwettable material with reversible and controllable water wettability can be applied in efficient and continuous separation of multiple types of oil/water mixtures, especially the highly emulsified oil/water emulsions, via in situ or ex situ wettability change. To our knowledge, the smart material with the wetting property of superamphiphobicity that can be used for continuous emulsified wastewater purification has been rarely discussed in the emerging research works. In addition, the as-prepared material presents universal applicability to diversiform substrates and exhibits robust durability and stability against high-concentration salt solutions and rigorous mechanical abrasion. All of these above-mentioned advantages indicate that the as-prepared superwettable material will hold great potential in various practical applications, including oily wastewater remediation, smart aquatic device fabrication, liquid droplet manipulation, guiding liquid movement, and optimizing multiple operations in industrial fields.

Smart materials: Properties, design and mechatronic applications:

Abstract: This paper describes the properties and the engineering applications of the smart materials, especially in the mechatronics field. Even though there are several smart materials which all are very i...

Smart Piezoelectric Nanohybrid of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Barium Titanate for Stimulated Cartilage Regeneration

Abstract: Piezoelectric materials strive to articulate smart materials and transduce electric fields by applying mechanical pressure and vice versa. This study demarcates augmented cartilage regeneration fro...

Vibration Controllability of Sandwich Structures with Smart Materials of Electrorheological Fluids and Magnetorheological Materials: A Review

Abstract: Vibration control is very significant issue in various engineering fields such as flexible structures, rotor systems, cable and bridge, and vehicle suspension. So far, three different recipes to suppress or control unwanted vibrations are used: passive, semi-active and active. As well known, the passive method has several limitations, such as the lack of real-time avoidance of the time-varying resonances. On the one hand, active vibration control method is very effective, but it is not attractive in terms of cost due to the use of several actuators and sensors. Therefore, recently semi-active vibration control method is popularly used in many practical environments. This article reviews vibration control of flexible structures using the semi-active method associated with smart materials of electrorheological fluids, magnetorheological fluids and magnetorheological elastomers. Modal characteristics of beam, shell and plate incorporating the core (or layer) of smart materials are deeply investigated and discussed in terms of field-dependent controllability. The field-dependent natural frequency and damping property of the sandwich beam type, plate type and shell type are experimentally identified. Subsequently, an appropriate control scheme based on the field-dependent modal properties is formulated to avoid the resonance behavior. In addition, several sandwich beams which are partially filled and fully filled with the magnetorheological fluid are investigated to understand the effectiveness of the modal property change. It has shown that both damping and stiffness properties of the sandwich structures can be effectively controlled by several ways: the change of the field intensity, the location of cores zones, the partial and full treatment and boundary conditions of the structures. In addition, it has identified that mode shapes of the sandwich plates featuring electrorheological core can be partially and fully controlled by applying the input field to an appropriate zone. Smart flexible structures associated with the field-responsive materials can be effectively used for vibration control due to its controllability of the stiffness and damping as well. However, to successfully implement in real environment, a more sophisticated analytical model considering the microscopic aspects of the particle motions needs to developed. Moreover, the field-dependent bucking problem and acoustic characteristics of smart structures subjected to external disturbances need to be explored.

Influence of fused deposition modeling process parameters on the transformation of 4D printed morphing structures

Abstract: 4D printing combines additive layer manufacturing processes with smart materials to create structures that are able to change shape or properties over time under the influence of environmental stimuli. The article presents 3D printed multi-material shape-variable structures imitating a hinge. Fused deposition modelling was used because it provides the ability to preprogram structures during the printing process by varying printing parameters. The structures are printed with PLA and TPU and remain flat after printing until they are exposed to a stimulus - heat. The main objective of this article is to present the possibilities of the aforementioned preprogramming step which can be adapted by varying the printing process and design parameters of the printed part. Experimental results are presented investigating the influence of printing speed, temperature of the build plate and number of active layers in the structure. Furthermore, the repeatability of deformations after a small number of cycles is investigated. The obtained results prove that the deformation of the structures can be controlled by printing parameters and a variety of bending degrees can be obtained by manipulating them. Hot water is used as a stimulus in the study to activate the structures but it is believed that other direct and indirect heating sources are also applicable. The research could help predict the behaviour of deformation of shape-morphing structures by selecting certain printing and design parameter values.