Showing papers on "Smart material published in 2022"

Bistable Morphing Composites for Energy-Harvesting Applications

Abstract: Bistable morphing composites have shown promising applications in energy harvesting due to their capabilities to change their shape and maintain two different states without any external loading. In this review article, the application of these composites in energy harvesting is discussed. Actuating techniques used to change the shape of a composite structure from one state to another is discussed. Mathematical modeling of the dynamic behavior of these composite structures is explained. Finally, the applications of artificial-intelligence techniques to optimize the design of bistable structures and to predict their response under different actuating schemes are discussed.

Disulfide-Mediated Reversible Polymerization toward Intrinsically Dynamic Smart Materials.

Abstract: The development of a dynamic chemistry toolbox to endow materials dynamic behavior has been key to the rational design of future smart materials. The rise of supramolecular and dynamic covalent chemistry offers many approaches to the construction of dynamic polymers and materials that can adapt, respond, repair, and recycle. Within this toolbox, the building blocks based on 1,2-dithiolanes have become an important scaffold, featuring their reversible polymerization mediated by dynamic covalent disulfide bonds, which enables a unique class of dynamic materials at the intersection of supramolecular polymers and adaptable covalent networks. This Perspective aims to explore the dynamic chemistry of 1,2-dithiolanes as a versatile structural unit for the design of smart materials by summarizing the state of the art as well as providing an overview of the fundamental challenges involved in this research area and its potential future directions.

Bistable and Multistable Actuators for Soft Robots: Structures, Materials, and Functionalities

Abstract: Snap‐through bistability is often observed in nature (e.g., fast snapping to closure of Venus flytrap) and the life (e.g., bottle caps and hair clippers). Recently, harnessing bistability and multistability in different structures and soft materials has attracted growing interest for high‐performance soft actuators and soft robots. They have demonstrated broad and unique applications in high‐speed locomotion on land and under water, adaptive sensing and fast grasping, shape reconfiguration, electronics‐free controls with a single input, and logic computation. Here, an overview of integrating bistable and multistable structures with soft actuating materials for diverse soft actuators and soft/flexible robots is given. The mechanics‐guided structural design principles for five categories of basic bistable elements from 1D to 3D (i.e., constrained beams, curved plates, dome shells, compliant mechanisms of linkages with flexible hinges and deformable origami, and balloon structures) are first presented, alongside brief discussions of typical soft actuating materials (i.e., fluidic elastomers and stimuli‐responsive materials such as electro‐, photo‐, thermo‐, magnetic‐, and hydro‐responsive polymers). Following that, integrating these soft materials with each category of bistable elements for soft bistable and multistable actuators and their diverse robotic applications are discussed. To conclude, perspectives on the challenges and opportunities in this emerging field are considered.

Mechanochromic, Shape‐Programmable and Self‐Healable Cholesteric Liquid Crystal Elastomers Enabled by Dynamic Covalent Boronic Ester Bonds

Abstract: Endowing a cholesteric liquid crystal elastomer (CLCE) exhibiting a helicoidal nanostructure with dynamically tailorable functionalities is of paramount significance for its emerging applications in diverse fields such as adaptive optics and soft robotics. Here, a mechanochromic, shape-programmable and self-healable CLCE is judiciously designed and synthesized through integrating dynamic covalent boronic ester bonds into the main-chain CLCE polymer network. The circularly polarized reflection of CLCEs can be reversibly and dynamically tuned across the entire visible spectrum by mechanical stretching. Thanks to the introduction of dynamic boronic ester bonds, the CLCEs were found to show robust reprogrammable and self-healing capabilities. The research disclosed herein can provide new insights into the development of 4D (color and 3D shape) programmable photonic actuators towards bioinspired camouflage, adaptive optical systems, and next-generation intelligent machines.

Recent Progress in Smart Polymeric Gel‐Based Information Storage for Anti‐Counterfeiting

Abstract: Information security protection has a tremendous impact on human life, social stability and national security, leading to the rapid development of anti‐counterfeiting materials and related techniques. However, the traditional stored information on hard or dry media is often static and lacks functions, which makes it challenging to deal with increasing and powerful counterfeiting technologies. Modified intelligent polymeric gels exhibit color changes and shape morphing under external stimuli, which give them great potential for applications in information storage. This paper provides an overview of the latest progress in polymeric gel‐based information storage materials in relation to counterfeiting. Following a brief introduction of anti‐counterfeiting materials, the preparation methods for intelligent gels with adjustable colors (e.g., chemical colors and physical colors) and various encryption/decryption modes involving dimensions and diverse colors are outlined. Finally, the challenges and prospects for information storage and anti‐counterfeiting based on smart gels are discussed.

Stimuli-Responsive Crystalline Smart Materials: From Rational Design and Fabrication to Applications.

Abstract: ConspectusStimuli-responsive smart materials that can undergo reversible chemical/physical changes under external stimuli such as mechanical stress, heat, light, gas, electricity, and pH, are currently attracting increasing attention in the fields of sensors, actuators, optoelectronic devices, information storage, medical applications, and so forth. The current smart materials mostly concentrate on polymers, carbon materials, crystalline liquids, and hydrogels, which have no or low structural order (i.e., the responsive groups/moieties are disorderly in the structures), inevitably introducing deficiencies such as a relatively low response speeds, energy transformation inefficiencies, and unclear structure-property relationships. Consequently, crystalline materials with well-defined and regular molecular arrays can offer a new opportunity to create novel smart materials with improved stimuli-responsive performance. Crystalline materials include framework materials (e.g., metal-organic frameworks, MOFs; covalent organic frameworks, COFs) and molecular crystals (e.g., organic molecules and molecular cages), which have obvious advantages as smart materials compared to amorphous materials. For example, responsive groups/moieties can be uniformly installed in the skeleton of the crystal materials to form ordered molecular arrays, making energy transfer between external-stimulus signals and responsive sites much faster and more efficiently. Besides that, the well-defined structures facilitate in situ characterization of their structural transformation at the molecular level by means of various techniques and high-tech equipment such as in situ spectra and single-crystal/powder X-ray diffraction, thus benefiting the investigation and understanding of the mechanism behind the stimuli-responsive behaviors and structure-property relationships. Nevertheless, some unsolved challenges remain for crystalline smart materials (CSMs), hampering the fabrication of smart material systems for practical applications. For instance, as the materials' crystallinity increases, their processability and mechanical properties usually decrease, unavoidably hindering their practical application. Moreover, crystalline smart materials mostly exist as micro/nanosized powders, which are difficult to make stimuli-responsive on the macroscale. Thus, developing strategies that can balance the materials' crystallinity and processability and establishing macroscale smart material systems are of great significance for practical applications.In this Account, we mainly summarize the recent research progress achieved by our groups, including (i) the rational design and fabrication of new stimuli-responsive crystalline smart materials, including molecular crystals and framework materials, and an in-depth investigation of their response mechanism and structure-property relationship and (ii) creating chemical/physical modification strategies to improve the processability and mechanical properties for crystalline materials and establishing macroscale smart systems for practical applications. Overall, this Account summarizes the state-of-the-art progress of stimuli-responsive crystalline smart materials and points out the existing challenges and future development directions in the field.

Graphene and CNT‐Based Smart Fiber‐Reinforced Composites: A Review

Abstract: Multifunctional fiber‐reinforced polymer (FRP) composites provide an ideal platform for next‐generation smart composites applications including structural health monitoring, electrical and thermal conductivity, energy storage and harvesting, and electromagnetic interference shielding without compromising their mechanical properties. Recent progress in carbon‐based nanomaterials such as graphene and carbon nanotubes (CNTs) has enabled the development of many novel multifunctional composites with excellent mechanical, electrical, and thermal properties. However, the effective incorporation of such carbon nanomaterials into FRP composites using scalable, high‐speed, and cost‐effective manufacturing without compromising their performance is challenging. This review summarizes the recent progress on graphene and CNT‐based FRP composites, their manufacturing techniques, and their applications in smart composites. Current technical challenges and future perspectives on smart FRP composites research to facilitate an essential step toward moving from research and development‐based smart composites to industrial‐scale mass production are also discussed.

4D Printing of Multiple Shape Memory Polymer and Nanocomposites with Biocompatible, Programmable and Selectively Actuated Properties

Abstract: 4D printing of shape memory polymers (SMPs) endows the 3D printed structures with tunable shape-changing behavior and functionalities that opens up new avenues towards intelligent devices. Multiple-SMPs, specially, could memorize more than two shapes that have greatly extended the performance of 4D printed structures. However, the actuation to trigger the shape change of 4D printed multiple-SMPs is usually by direct heating to different temperatures. It hasn’t brought the full superiority of the programmability of multiple-SMPs with distinct responsive regions that could be sequentially and selectively actuated by various stimuli. Besides, the functionality of multi-material based additive manufacturing is another area that has not been fully developed. Herein, 4D printing of poly (D,L-lactide-co-trimethylene carbonate) (PLMC)/poly (trimethylene carbonate) (PTMC)/Fe3O4 multi-material with multiple shape-changing capabilities under sequential stimuli of remotely magnetic field and heat was achieved. At first, we optimized the composition of pure SMP to fine tune the multiple shape memory effect and quantitatively characterized the shape recovery by stepwise heating. Then with the addition of Fe3O4 nanoparticles, the multi-material distribution of 4D printed structure consisting of multiple-SMP and its nanocomposites was designed. The integration of multi-material additive manufacturing with multiple shape memory effect extends the shape transformation to quintuple complex shapes with accurate and local controllability under selective multi-stimuli. The 4D printed multiple-SMP and its nanocomposites with simultaneously thermo- and magnetic- responsive shape-changing capability also demonstrated excellent biocompatibility. This work thus offers a feasible and robust approach for 4D printing of multi-functional devices for broad applications in entertainment, robotics, biomedical field and beyond.

Advances in smart/functional cementitious composites incorporating various carbon nanomaterials

Abstract: Conductive carbon nanomaterials have been extensively developed for smart cementitious composites to gain multifunctionalities (e.g. self-sensing, self-healing, self-heating, and electromagnetic interference shielding). This paper critically reviewed dispersion and percolation of 0 dimension (0D), 1 dimension (1D) and 2 dimensions (2D) carbon materials used in cementitious composites and their effects on the electrical and piezoresistive performances. The different dispersion methods summarized are from mechanical dispersion , ultrasonic and high shearing, chemical modification, mineral additives, to carbon materials at multiple dimensions and hybrid dispersion methods. The electrical resistivity and piezoresistivity of cementitious composites with single carbon material or hybrid carbon materials are comprehensively analysed and compared in terms of efficiency and self-sensing mechanism. Furthermore, the existing theoretical modelling studies have been reviewed, indicating that many factors related to the electrical and piezoresistive behaviours, such as water content and nanocomposite agglomeration, have not been considered yet. Although some previous studies demonstrated the potential of applying conductive cementitious composites for self-sensing or heating pavements, further explorations still should be conducted on sustainable and economical manufacturing. Subsequently, the challenges and perspectives of the self-sensing stability, data acquisition system and sensor configuration are proposed with potential solutions for future smart infrastructure. • Uniform dispersion of nanocarbon materials is responsible for electrical and piezoresistive properties of concrete. • Both CNT and 2D GNP can improve the electrical conductivity and piezoresistivity of cementitious composites. • Type and content of conductors, frequency and intensity of input power affect conductivity and piezoresistivity. • Further explorations are needed to develop smart concrete in terms of sustainability, low-cost, and field applications.

Alginate-Based Smart Materials and Their Application: Recent Advances and Perspectives

Abstract: Nature produces materials using available molecular building blocks following a bottom-up approach. These materials are formed with great precision and flexibility in a controlled manner. This approach offers the inspiration for manufacturing new artificial materials and devices. Synthetic artificial materials can find many important applications ranging from personalized therapeutics to solutions for environmental problems. Among these materials, responsive synthetic materials are capable of changing their structure and/or properties in response to external stimuli, and hence are termed "smart" materials. Herein, this review focuses on alginate-based smart materials and their stimuli-responsive preparation, fragmentation, and applications in diverse fields from drug delivery and tissue engineering to water purification and environmental remediation. In the first part of this report, we review stimuli-induced preparation of alginate-based materials. Stimuli-triggered decomposition of alginate materials in a controlled fashion is documented in the second part, followed by the application of smart alginate materials in diverse fields. Because of their biocompatibility, easy accessibility, and simple techniques of material formation, alginates can provide solutions for several present and future problems of humankind. However, new research is needed for novel alginate-based materials with new functionalities and well-defined properties for targeted applications.

Photoprogrammable Moisture-Responsive Actuation of a Shape Memory Polymer Film.

Abstract: Humidity-responsive polymeric actuators have gained considerable interest due to their great potential in the fields including soft robotics, artificial muscles, smart sensors, and actuators. However, most of them can only exhibit invariable shape changes, which severely restricts their further exploration and practical use. Herein, we report that programmable humidity-responsive actuating behaviors can be realized by introducing photoprogrammable hygroscopic patterns into shape memory polymers. Poly(ethylene-co-acrylic acid) is selected as a model polymer and the solvent-processed thin films are soft and elastic, whose external shapes can be programmed by a modified shape memory process. On another aspect, an Fe3+-carboxylate coordinating network formed by surface treatments can be spatially dissociated under UV, resulting in transient hygroscopic gradients as active joints for moisture-driven actuation. Moreover, we show that the shape memory effect can be an effective means to adjust the direction as well as the amplitude of the moisture-driven actuating behavior. The proposed strategy is convenient and can be generally extended to other shape memory polymers to realize programmable moisture-responsive actuating behaviors.

Near-Infrared Light-Driven Shape-Programmable Hydrogel Actuators Loaded with Metal-Organic Frameworks.

Abstract: Shape-programmable hydrogel-based soft actuators that can adaptively respond to external stimuli are of paramount significance for the development of bioinspired aquatic smart soft robots. Herein, we report the design and synthesis of near-infrared (NIR) light-driven hydrogel actuators through in situ photopolymerization of poly(N-isopropylacrylamide) (PNIPAM) hydrogels loaded with metal-organic frameworks (MOFs) onto the surface of the poly(dimethylsiloxane) (PDMS) thin film. The MOFs can not only function as an excellent photothermal nanotransducer but also accelerate the adsorption/desorption of water due to their porous nanostructure, which speeds up the response rate of the actuators. Shape-programmable hydrogel actuators are fabricated by tailoring the patterning of PDMS thin film, and thus different shape-morphing modes such as directional bending and chiral twisting are observed under the NIR light irradiations. As the proof-of-concept demonstrations, an artificial hand, biomimetic mimosa, and flower are conceptualized with light-driven MOF-containing hydrogel actuators. Interestingly, we are able to achieve an octopus-inspired light-driven soft swimmer upon cyclic NIR illumination due to the fast photoresponsiveness of as-prepared hydrogel actuators. This work can offer insights for fabricating programmable and reconfigurable smart aquatic soft actuators, thus shining a light into their potential applications in emerging fields including soft robots, biomedical devices, and beyond.

Actuation of Liquid Crystalline Elastomers at or Below Ambient Temperature.

Abstract: Liquid crystal elastomers (LCE) are an emerging class of material actuators. LCE undergo macroscopic dimensional changes when subject to a stimulus. The large stimuli-response of LCE is associated with thermotropic disruption of order. Historically, comparatively high temperatures are required to disrupt orientation in LCE to achieve meaningful work output. Here, we introduce a materials chemistry to prepare LCE via thiol-Michael/thiol-ene reactions that actuate at or below ambient temperature. Alignment was imparted to the LCE by mechanical alignment and 3-D printing. The LCE materials detailed here achieve strains of 40% with a maximum deformation rate of 6.5%˚C -1 . The functional utility of the tunability of the thermotropic response of these materials is illustrated in reconfiguration triggered via body heat and sequential actuation of a multi-material element.

Reversible energy absorption of elasto-plastic auxetic, hexagonal, and AuxHex structures fabricated by FDM 4D printing

Abstract: Abstract The present study aims at introducing reconfigurable mechanical metamaterials by utilising four-dimensional (4D) printing process for recoverable energy dissipation and absorption applications with shape memory effects. The architected mechanical metamaterials are designed as a repeating arrangement of re-entrant auxetic, hexagonal, and AuxHex unit-cells and manufactured using 3D printing fused deposition modelling process. The AuxHex cellular structure is composed of auxetic re-entrant and hexagonal components. Architected cellular metamaterials are developed based on a comprehension of the elasto-plastic features of shape memory polylactic acid materials and cold programming deduced from theory and experiments. Computational models based on ABAQUS/Standard are used to simulate the mechanical properties of the 4D-printed mechanical metamaterials under quasi-static uniaxial compression loading, and the results are validated by experimental data. Research trials show that metamaterial with re-entrant auxetic unit-cells has better energy absorption capability compared to the other structures studied in this paper, mainly because of the unique deformation mechanisms of unit-cells. It is shown that mechanical metamaterials with elasto-plastic behaviors exhibit mechanical hysteresis and energy dissipation when undergoing a loading-unloading cycle. It is experimentally revealed that the residual plastic strain and dissipation processes induced by cold programming are completely reversible through simple heating. The results and concepts presented in this work can potentially be useful towards 4D printing reconfigurable cellular structures for reversible energy absorption and dissipation engineering applications.

4D printing technology in medical engineering: a narrative review

Abstract: Abstract The addition of the time dimension to three-dimensional (3D) printing has introduced four-dimensional (4D) printing technology, which has gained considerable attention in different fields such as medical, art, and engineering. Nowadays, bioscience has introduced some ideas which can be fulfilled by 4D printing. Blending time with variations caused by the situation has many beneficial aspects such as perceptibility and adaptability. Since 4D printing can create a dynamic structure with stimuli-responsive materials, the applications of smart materials, stimulus, and 3D printing are the effective criteria in 4D printing technology. Smart materials with their flexible properties can reshape, recolor, or change function under the effect of the internal or exterior stimuli. Thus, an attractive prospect in the medical field is the integration of the 4D printing approach along with smart materials. This research aims to show the most recent applications of 4D printing technology and smart materials in medical engineering which can show better prospective of 4D printing applications in the future. Also, it describes smart medical implants, tissue engineering, and bioprinting and how they are being used for the 4D printing approach in medical engineering applications. In this regard, a particular emphasis is dedicated to the latest progress in the innovation and development of stimuli-responsive materials that are activated and respond over time to physical, chemical, and biological stimuli and their exploitation through 3D printing methods to fabrication 4D printing smart parts such as intelligent tissue-engineered scaffolds, smart orthopedic implants, and targeted drug delivery systems. On the other hand, major challenges in this technology are explained along with some suggestions for future works to address existing limitations. It is worth noting that despite significant research that has been carried out into 4D printing, it might be more valuable if some investigation is done into 4D bio-printing applications and how this approach will be developed.

Advances in 4D Printed Shape Memory Polymers: From 3D Printing, Smart Excitation, and Response to Applications

Abstract: Shape memory polymer (SMP) is a smart material that can revert from a temporary shape to a permanent shape under external stimuli, showing great potential for applications in biomedical, aerospace, and intelligent robotics fields. In recent years, with the in‐depth combination of SMP and 4D printing, many breakthroughs have been made in smart manufacturing and multifunctional integrated response. Here, the authors overview the research progress of 4D printing SMP, focusing on the diverse excitation methods, intelligent response deformation modes, and applications of 4D printing SMP. Finally, they point out the problems and future development directions of 4D printing SMP in terms of the printing process, SMP modification, structural design, and multifunctional coupling design.

4D printing of mechanically robust PLA/TPU/Fe3O4 magneto-responsive shape memory polymers for smart structures

Abstract: The integration of magneto-responsive shape memory polymers (SMPs) into 4D printing provides novel opportunities to create innovative and intelligent products controlled in a contactless method. In this study, a promising SMPs with robustly mechanical property and magneto-responsive behavior were proposed and fabricated into 3D printing feedstock based on polylactic acid (PLA), thermoplastic polyurethane (TPU) and Fe 3 O 4 particles. Results revealed that the 3D-printed PLA/TPU/Fe 3 O 4 possessed robust tensile strength and modulus with a homogeneous distribution of magnetic particles in polymer blends. Also, PLA/TPU/Fe 3 O 4 exhibited excellent shape fix ratio (∼100%), recovery ratio (>91%) and rapid magnetic response within as short as 40 s, suggesting the high efficiency of heat generation by magnetic particles. Moreover, smart structures including honeycomb and bionic flower-like model were designed and printed as an original shape. After programmed by an external force, the folded lattice structure at the temporary shape could recovered completely under a contactless magnetic field. The flower-bud structure sequentially restored layer-by-layer controlled by using three pedals with varied Fe 3 O 4 composites. Consequently, the high-load capacity, fast magneto-responsive behavior and high recovery performance of the proposed multi-material have great potentials in actuator or robots applications via 3D printing. • The PLA/TPU/Fe 3 O 4 composites with varying Fe 3 O 4 contents are capable to fabricate filaments for fused filament (FFF) 3D printing. • PLA/TPU/Fe 3 O 4 composite filaments show fast magneto-responsive shape memory and recovery behavior by heat or magneto stimulation. • Facile transformation are perfectly realized between designed structures with temporary shape fixed by heat or external force and then magneto-stimulated into original shape.

Sustainable Triboelectric Materials for Smart Active Sensing Systems

Abstract: With the vigorous development of the Internet of Things and artificial intelligence, the active sensing system based on triboelectric nanogenerators plays an excellent performance potential and application value as a pioneering technology for smart manufacturing. Nevertheless, achieving material innovation to strike a good balance between active sensing systems and environmental friendliness remains a difficult task. As the most abundant biopolymer on earth, the sustainability potential and excellent performance of cellulose are of great importance for the development of smart sensing systems. This review intends to provide a new perspective on the sustainability of smart active sensing systems to design and fabricate cellulosic triboelectric materials for self‐powered sensing systems. Herein, the structure and advantageous properties of cellulosic triboelectric materials are briefly described. Furthermore, the structure–property–application relationship of the materials is addressed from the perspective of material design and structure optimization. Next, the latest applications of cellulose triboelectric materials are comprehensively described in smart sensing fields such as environmental monitoring, smart home, smart medical, human–machine interaction, and the Internet of everything. Lastly, the current challenges and future developments of cellulose triboelectric materials for smart sensor systems are presented.

Designable Micro‐/Nano‐Structured Smart Polymeric Materials

Abstract: Smart polymeric materials with dynamically tunable physico-chemical characteristics in response to changes of environmental stimuli, have received considerable attention in myriad fields. The diverse combination of their micro-/nano-structural and molecular designs creates promising and exciting opportunities for exploiting advanced smart polymeric materials. Engineering micro-/nano-structures into smart polymeric materials with elaborate molecular design enables intricate coordination between their structures and molecular-level response to cooperatively realize smart functions for practical applications. In this review, recent progresses of smart polymeric materials that combine micro-/nano-structures and molecular design to achieve designed advanced functions are highlighted. Smart hydrogels, gating membranes, gratings, milli-particles, micro-particles and microvalves are employed as typical examples to introduce their design and fabrication strategies. Meanwhile, the key roles of interplay between their micro-/nano-structures and responsive properties to realize the desired functions for their applications are emphasized. Finally, perspectives on the current challenges and opportunities of micro-/nano-structured smart polymeric materials for their future development are presented.

A Review of Smart Materials for the Boost of Soft Actuators, Soft Sensors, and Robotics Applications

Abstract: Abstract With the advance of smart material science, robotics is evolving from rigid robots to soft robots. Compared to rigid robots, soft robots can safely interact with the environment, easily navigate in unstructured fields, and be minimized to operate in narrow spaces, owning to the new actuation and sensing technologies developed by the smart materials. In the review, different actuation and sensing technologies based on different smart materials are analyzed and summarized. According to the driving or feedback signals, actuators are categorized into electrically responsive actuators, thermally responsive actuators, magnetically responsive actuators, and photoresponsive actuators; sensors are categorized into resistive sensors, capacitive sensors, magnetic sensors, and optical waveguide sensors. After introducing the principle and several robotic prototypes of some typical materials in each category of the actuators and sensors. The advantages and disadvantages of the actuators and sensors are compared based on the categories, and their potential applications in robotics are also presented.

Reconfigurable 4D Printing of Reprocessable and Mechanically Strong Polythiourethane Covalent Adaptable Networks

Abstract: 4D printing has attracted tremendous interest because of its potential applications in smart devices, biomedical and tissue engineering. However, conventional shape memory polymers suffer from the single permanent shape and recovery direction, the flexibility of 4D printing is significantly limited. Besides, the cross-linked networks of photocuring 3D-printed objects cannot be reprocessed or repaired. To address these issues, the dynamic thiocarbamate bonds are introduced into the photocurable methacrylate to prepare reprocessable and self-healable 4D printing polythiourethane (4DP-PTU) with Young's modulus of 1.2 GPa and tensile strength of 61.9 MPa. The printed objects can be easily repaired by reprinting on the damaged surface. The shape memorized 4DP-PTU features high shape fixity and shape recovery, and reconfigurable permanent shape brought by the solid-state plasticity. A dual-mode triggered alarm is obtained by the incorporation of carbon nanotubes to demonstrate the potential application in smart alarms for warning of laser exposure or fire case. Moreover, the surface wettability and cell adhesion performance of 4DP-PTU with excellent biocompatibility can be facilely adjusted through the exchange reaction with sulfhydryl compounds. Accordingly, 4DP-PTU may show vast potential applications in the field of robotics, smart alarm, bio-implants and in solving the environmental challenges of 3D-printed products.

4D printing of electroactive shape-changing composite structures and their programmable behaviors

Abstract: 4D printing is an advanced manufacturing technology that combines the convenience of additive manufacturing and uses stimuli-responsive materials, which has great application potentials in the field of smart structures. Using electroactive shape memory polymer composites (SMPCs), smart devices with remote control capabilities without a heat source can be prepared by 4D printing. In this work, a variety of 4D printed structures based on PLA/CNT composites were fabricated by FDM. Electroactive SMPC filaments with different CNT contents were prepared, and their electrical, thermal, and shape-memory properties were investigated. Moreover, a series of 2D and 3D printed complex structures were designed and manufactured to realize their shape recovery behavior under the electrical field. The relationship between the electroactive shape-memory performance of 4D printed structures, structural design, and printing parameters was obtained. This work could provide a new feasible way for the design and manufacturing of electroactive devices in the future.