Memory Materials Research Articles

4D Fabrication of Two-Way Shape Memory Polymeric Composites by Electrospinning and Melt Electrowriting.

This work presents a new method for 4D fabrication of two-way shape memory materials that are capable of reversible shapeshifting right after manufacturing, upon application of proper heating and cooling cycles. The innovative solution presented here consists in the combination of highly stretched electrospun shape memory polymer (SMP) nanofibers with a melt electrowritten elastomer. More specifically, the stretched nanofibers are made of a biocompatible thermoplastic polyurethane (TPU) with crystallizable soft segments, undergoing melt-induced contraction and crystallization-induced elongation upon heating and cooling, respectively. Reversible actuation during crystallization becomes possible due to the elastic recovery of the elastomer component, obtained by melt electrowriting of a commercial TPU filament. Thanks to the design freedom offered by additive manufacturing, the elastomer structure also has the role of guiding the shape transformation. Electrospinning and melt electrowriting process parameters are set up so to obtain smart 4D objects capable of two-way shape memory effect (SME), and the possibility of reversible and repeatable actuation is demonstrated. The two components are then combined in different proportions with the aim of tailoring the two-way SME, taking into account the effect of design parameters such as the SMP content, the elastomer pattern, and the composite thickness.

Photoelectric dual-mode triggered phase change materials for all-weather personal thermal management and shape memory

To cope with the demand of more complex and variable applications, it is urgent to develop dual-mode triggered, breathable, and shape-memory wearable heaters for all-weather personal thermal management of composite phase change materials (PCMs). Herein, after high-temperature carbonization of ZnCo-MOF (metal–organic framework) nanosheet array grown in situ on flexible and breathable carbon cloth (CC) and subsequent encapsulation of polyethylene glycol (PEG), the as-prepared PEG/CC@Co/CNT (carbon nanotube) composite PCMs exhibited good breathability, mechanical strength (tensile strength of 9.15 MPa), thermal energy storage density (114.19 J/g), and shape memory due to the synergy of flexible CC skeleton and rigid PEG. More importantly, composite PCMs possessed excellent solar-thermal (93.7 %, 100 mW/cm2) and electro-thermals (94.5 %, 2.0 V) conversion and storage capacity, benefiting from the conjugation effect of high graphitized carbon/carbon heterostructure with fast electron/photon/phonon transmission and the localized surface plasmon resonance effect of Co nanoparticles. Therefore, the integration of solar heating and Joule heating into breathable composite PCMs can be accurately used for next-generation all-weather, all-season, dual-mode triggered personal thermal management, including indoor/outdoor, daytime/night, rainy/cloudy and other complex and changeable scenarios.

Datafication of audiovisual archives: from practice mapping to a thinking model

PurposeRecent archiving and curatorial practices took advantage of the advancement in digital technologies, creating immersive and interactive experiences to emphasize the plurality of memory materials, encourage personalized sense-making and extract, manage and share the ever-growing surrounding knowledge. Audiovisual (AV) content, with its growing importance and popularity, is less explored on that end than texts and images. This paper examines the trend of datafication in AV archives and answers the critical question, “What to extract from AV materials and why?”.Design/methodology/approachThis study roots in a comprehensive state-of-the-art review of digital methods and curatorial practices in AV archives. The thinking model for mapping AV archive data to purposes is based on pre-existing models for understanding multimedia content and metadata standards.FindingsThe thinking model connects AV content descriptors (data perspective) and purposes (curatorial perspective) and provides a theoretical map of how information extracted from AV archives should be fused and embedded for memory institutions. The model is constructed by looking into the three broad dimensions of audiovisual content – archival, affective and aesthetic, social and historical.Originality/valueThis paper contributes uniquely to the intersection of computational archives, audiovisual content and public sense-making experiences. It provides updates and insights to work towards datafied AV archives and cope with the increasing needs in the sense-making end using AV archives.

Charge-Localized Retention and Long-Term Memory Enabled by Cooperating Sterically Confined Molecular Crystallization with Spiro[fluorene-9,9'-xanthene]-Based Csp3-Hindrance.

Charge localization of memory materials plays a crucial role in the endurance and retention ability of organic nonvolatile memory, which is completely opposite from the charge delocalization of high-mobility materials. However, charge transfer of both though-space and through-bond based on molecular design principles still faces challenges. Herein, a nonplanar wide-bandgap semiconductor with Csp3-hindrance (DOCH3-DDPA-SFX) has been designed and synthesized. An effective crystallization effect of self-assembled two-dimensional nanosheets on charge trapping dynamics and kinetics is visualized by Kelvin probe force microscopy (KPFM). The trapped charges are localized completely on a single nanosheet, which has better charge trapping and retention properties than an amorphous film. Meanwhile, crystallization also greatly improves structure stability. Combining DFT theoretical calculations, the mechanisms of localization and long-term retention are discussed. The steric crystallization effects on the charge localization will guide the effective design of single-component semiconducting charge-memory materials by molecular assembly and aggregate control for high-performance organic memory.

Nanocomposites of Nanocarbon Functionalized Carbon Fibers—Manufacturing to Methodological Applications

Abstract Carbon fibers have been technically applied in high performance materials and industrial scale applications. Importantly, carbon fiber reinforced composite materials have found applications in aerospace industries. These properties of carbon fiber reinforced composites depend upon the carbon fiber features such as length, orientation, surface properties, adhesion with matrices, etc. To improve the surface properties of carbon fibers and adhesion and interactions with polymers, fiber modification has been suggested as an efficient approach. Carbon nanoparticle or nanocarbon functionalized carbon fibers have been manufactured using various facile physical and chemical approaches such as electrospraying, electrophoretic deposition, chemical vapor deposition, etc. Consequently, the modified carbon fibers have nanocarbon nanoparticles such as graphene, carbon nanotube, nanodiamond, fullerene, and other nanocarbons deposited on the fiber surface. These nanocarbon nanoparticles have fine capability to improve interfacial linking of carbon fibers with the polymer matrices. The chemical vapor deposition has been adopted for uniform deposition of nanocarbon on carbon fibers and chemical methods involving physical or chemical modification have also been frequently used. The resulting advanced epoxy/carbon fiber/nanocarbon composites revealed improved tensile and physical profiles. This review basically aims manufacturing and technical aspects of polymer/fiber/nanofiller nanocomposites toward the development of high performance structures. The resulting morphology, strength, modulus, toughness, thermal stability, and other physical features of the nanocarbon functionalized carbon fibers have been enhanced. In addition, the fabricated polymer/fiber/nanofiller nanocomposites have fine interfacial adhesion, matrix-nanofiller-filler compatibility, and other characteristics. The application areas of these nanomaterials have been found wide ranging including the strengthened engineering structures, supercapacitors, shape memory materials, and several others.

A review on CuAlNi shape memory alloys: Production methods, applications and current trends

Shape Memory Alloys (SMAs) are one sort of shape memory material (SMM) that “remembers” the initial shape when subjected to stimuli like magnetic or thermomechanical changes. Cu-based SMAs in the past decade have emerged successfully as potential materials in various applications such as Sensors, actuators, and high-damping materials. Cu-Al-Ni SMAs have received attention because they are more thermally stable than other Copper-based SMAs. Cu-Al-Ni SMA is an excellent candidate with excellent SME and super-elastic behaviour in the narrow temperature range of 373–473 K. Nickel is added in the binary system of Cu-Al to lower the high transformation temperature and stabilise the austenite phase. This Paper reviews Production Methods, Applications and Current Trends of CuAlNi SMA.

High-performance shape memory epoxy resin with high strength and toughness: Prepared by introducing hydrogen bonds through polycaprolactone and low melting point alloy

Epoxy resin (EP) as common polymers have attracted much attention in the field of shape memory materials due to their excellent properties. However, epoxy-based shape memory polymers suffer from a trade-off between strength, toughness, variable stiffness capability and shape memory properties, and thus are subject to significant limitations in their applications. In this paper, we propose a method to prepare epoxy composites with high strength and toughness and high shape memory properties by introducing a lot of hydrogen bonds. Hydrogen bonding is generated through polycaprolactone (PCL) induced EP phase separation. A low melting point alloy (L) was also added to enhance the shape memory properties of the composites. The synthesis mechanism of EP and the formation mechanism of hydrogen bonding were revealed. The effects of the introduction of hydrogen bonding on the mechanical properties, stiffness and shape memory properties of the composites were investigated. New ideas and design directions are provided for the optimisation of modification of high-performance shape memory epoxy resins.

Supplemental Material for Ensemble Memory of a Scene Interacts With Current Perception Regardless of Attentional Requirements

Supplemental Material for Ensemble Memory of a Scene Interacts With Current Perception Regardless of Attentional Requirements

Concept Design of a Smart Haptic Suit for a Biological Signal Recognition and Feedback to Human Body Movements

The ultimate purpose of monitoring bio-signals in the form of individually tailored clothing is to monitor an unconstrained bio-signals during the wearer's physiological activities and provide freedom of movement, thereby eliminating inconvenience in workspace of HMI (Human-Machine Interaction) or HRI (Human-Robot Interaction), and healthcare life. In the form of smart clothing for human collaboration industries or everyday life, there is a need to provide new sensitive and high accurate functions to the wearer while also faithfully performing the functions of existing clothing. In this respect, auxetic pattern-based sensors and actuators can be said to be one of the most promising candidates to be combined with smart wearable technology. There is an emerging need to research the concepts of these new sensors and actuators and present a paradigm for clothing research on innovative smart haptic suits. Accordingly, there is a need for a concept of smart haptic system suitable to meet the conditions of sensors and actuators with improved sensitivity, conductivity, and receptivity that can have characteristics such as microporosity, flexibility, and large surface area of nano and micro web structures. When measuring a bio-signal sensing and motion feedback using an electro-active structural pattern, the signal waveform can be confirmed to have a similar signal waveform to the measured signal through direct visual evaluation, and muscle signals for each body part can be measured using a commercialized sensor. The same signal can be confirmed. Through Pearson's correlation analysis using statistical analysis techniques, signal data between nano and micro web structure-based respiration sensors and existing respiration sensors showed significant correlation with each other, indicating respiration obtained from nano and micro web-based sensors. A theoretical model which predicts the actuation stroke of the system based on the material properties of the auxetic SMM (Shape Memory Material) and bias components as well as the geometry of the metamaterial system was developed.

Effects of energized treatment on electro trigger shape memory behavior

The shape memory polymers (SMPs) can be programmed to take temporary shapes and return to their original shape when subjected to external stimuli. Electrically triggered SMP has become an important branch of shape memory materials because of its advantages such as remote heating, fast response and local control. In this paper, a novel shape memory composite structure is prepared by using polylactic acid (PLA) as substrate and short carbon fiber (SCF) as conductive filler. The electrification treatment during the preparation process has a beneficial effect on the SCF arrangement. Compared with the sample without electrification treatment, the highest conductivity can be increased from 43.96 S/m to 66.67 S/m, and the performance is improved by 51.66 %. When the voltage is increased from 3 V to 8 V, the time to reach the glass transition temperature (Tg) is reduced by 62.22 %, and the shape memory recovery time is reduced by 53.68 %. The intelligent fixture based on the composite structure can realize the remote grasp of 3D printed balls with a diameter of 40 mm and a weight of 18.35 g under pressure, which fully proves the reliable electrically triggered shape memory performance of the composite structure and the great application potential in the field of robot gripper.

Unravelling the amorphous structure and crystallization mechanism of GeTe phase change memory materials

The reversible phase transitions in phase-change memory devices can switch on the order of nanoseconds, suggesting a close structural resemblance between the amorphous and crystalline phases. Despite this, the link between crystalline and amorphous tellurides is not fully understood nor quantified. Here we use in-situ high-temperature x-ray absorption spectroscopy (XAS) and theoretical calculations to quantify the amorphous structure of bulk and nanoscale GeTe. Based on XAS experiments, we develop a theoretical model of the amorphous GeTe structure, consisting of a disordered fcc-type Te sublattice and randomly arranged chains of Ge atoms in a tetrahedral coordination. Strikingly, our intuitive and scalable model provides an accurate description of the structural dynamics in phase-change memory materials, observed experimentally. Specifically, we present a detailed crystallization mechanism through the formation of an intermediate, partially stable ‘ideal glass’ state and demonstrate differences between bulk and nanoscale GeTe leading to size-dependent crystallization temperature.

Eco-Friendly Flame-Retardant Phase-Change Composite Films Based on Polyphosphazene/Phosphorene Hybrid Foam and Paraffin Wax for Light/Heat-Dual-Actuated Shape Memory.

Multiactuated shape memory materials are a class of promising intelligent materials that have received great interest in the fields of self-healing, anticounterfeiting, biomedical, soft robotic, and smart thermal management applications. To obtain a light/heat-dual-actuated shape memory material for thermal management applications in fire safety, we have designed a type of halogen-free flame-retardant phase-change composite film based on polyaryloxyphosphazene (PDAP)/phosphorene (PR) hybrid foam as a support material and paraffin wax (PW) as a phase-change material (PCM). PDAP was synthesized as a flexible foam matrix through the ring-opening polymerization of hexachlorocyclotriphosphazene, followed by a substitution reaction of aryloxy groups. The porosity of the PDAP foam is improved by introducing PR nanosheets, facilitating a high latent heat capacity of the PDAP-PR/PW composite films for thermal management applications. The PDAP-PR/PW composite films can implement rapid shape recovery within 65 s in the heating process, which is much shorter than that of the corresponding film without PR nanosheets (185 s). Furthermore, the PDAP-PR/PW composite films also exhibit light-actuated shape memory behavior thanks to their good solar-to-thermal energy absorption and conversion contributed by PR nanosheets as a highly effective photothermal material. More importantly, the presence of PR nanosheets imparts an excellent flame-retardant property to the PDAP-PR/PW composite films. The PDAP-PR/PW composite film can be self-extinguished within 2 s after the flame. Through an innovative integration of flexible polyphosphazene foam, PR nanosheets, and solid-liquid PCM to obtain a sensitive actuating response to light and heat, this study offers a new approach for developing multiactuated and eco-friendly flame-retardant shape memory materials to meet the requirement of applications with a requirement of fire safety in soft actuators, thermal therapy, control devices, and so on.

Design features of drilling equipment elements using materials with shape memory effect

Alloys exhibiting thermoelastic phase transformations are getting more and more used in different industries. This is due to the shape memory effect and pseudo-elasticity (sometimes termed “superelasticity”) they exhibit, which can considerably improve the performance characteristics of various technical systems. One of the highest reliability and durability criterias are applied to equipment for drilling oil and gas wells, and according to this the above-described smart materials and the phenomena they exhibit have been gradually implemented in the oil and gas industry. This article analyzes the developed design of roller cone bits elements and proposes its assembly method, and presents its comparison with currently existing designs. Computational research and computer analysis of a drilling equipment assembly containing parts made of shape memory materials were performed, these studies showed significant advantages of the proposed method.

Biodegradable photo-crosslinked polycaprolactone/polydopamine elastomers with excellent light driven programmable shape memory and chemical degradation properties

Fabrication of biodegradable shape memory polymer with remotely controllable shape actuation is of great significance in the biomedical field but remains challenging. Herein, we present a simple strategy to fabricate a monolayer-based stretchable and mechanically robust polycaprolactone/polydopamine elastomer via efficient thiol-ene click chemistry. The resultant elastomers exhibit desirable photothermal transfer efficiency and can enable rapid temperature increase over the melting temperature of polymeric matrix, and quantitative results demonstrate that the crosslinked film exhibited excellent shape memory properties with shape fixity (Rf) and shape recovery ratios (Rr) approaching 92.3 % and 95.6 %, respectively. Combined with photo stimuli, anisotropic polymer chain relaxation of the prestretched film can generate asymmetric contractions and eventually give rise to ut out-of-plane bending actuations upon photo stimulation, meanwhile, numerical simulation reveals the interaction mechanism of light with film. Beyond this, we further demonstrate that the bending angle is correlated with the parameters of prestretch strain, film thickness as well as irradiation time, and the maximum value can reach 158° with prestretch strain of 200 % and film thickness of 0.3 mm. In particular, the bent structures could be reversibly deformed into plane state via photo-directed corresponding opposite surfaces. Remarkably, the in vitro degradation properties of the elastomers on PBS-T buffer solutions demonstrated that the degradation was composed of induction stage and acceleration stage. This work will pave way for designing biodegradable light-induced shape memory materials toward biomedical device fields and so on.

Impact of CoFe2O4 Magnetic Nanoparticles on the Physical and Mechanical Properties and Shape Memory Effect of Polylactide

The acceleration in advancements of smart materials and non-contact controlled devices in the field of 4D printing is facilitated by the use of magnetically responsive shape memory polymer (SMP) composites. This study is dedicated to the development of promising shape memory materials based on polylactic acid (PLA) and cobalt ferrite (CoFe2O4) nanoparticles. The activation of the shape memory effect (SME) in magnetic nanoparticle composites was achieved by applying a high-frequency alternating magnetic field (HFAMF). The PLA/CoFe2O4 composites exhibited a remarkable shape recovery ratio (>84%) and underwent rapid heating when exposed to HFAMF. The interaction of these composites with mouse adipose-derived mesenchymal stem cells demonstrated adequate cytocompatibility. The rapid magnetosensitive behavior and high shape recovery characteristics of PLA/CoFe2O4 composites make them promising candidates for biomedical applications.

Catalyst-Free Cardanol-Based Epoxy Vitrimers for Self-Healing, Shape Memory, and Recyclable Materials.

Bio-based vitrimers present a promising solution to the issues associated with non-renewable and non-recyclable attributes of traditional thermosetting resins, showcasing extensive potential for diverse applications. However, their broader adoption has been hindered by the requirement for catalyst inclusion during the synthesis process. In this study, a cardanol-based curing agent with poly-hydroxy and tertiary amine structures was prepared by a clean synthetic method under the theory of click chemistry. The reaction of a cardanol-based curing agent with diglycidyl ether of bisphenol A formed catalyst-free, self-healing, and recyclable bio-based vitrimers. The poly-hydroxy and tertiary amine structures in the vitrimers promoted the curing of epoxy-carboxylic acid in the cross-linked network and served as internal catalysts of dynamic transesterification. In the absence of catalysts, the vitrimers network can achieve topological network rearrangement through dynamic transesterification, exhibiting excellent reprocessing performance. Moreover, the vitrimers exhibited faster stress relaxation (1500 s at 180 °C), lower activation energy (92.29 kJ·mol-1) and the tensile strength of the recycled material reached almost 100% of the original sample. This work offers a new method for preparing cardanol-based epoxy vitrimers that be used to make coatings, hydrogels, biomaterials, adhesives, and commodity plastics in the future.

Tailoring the time delay of deployable structures using the Intermediate Axis Theorem

Deployment techniques devised from compliant joints, shape memory materials, and inertial effects from rotational motion can be employed in deployable structures to realize a time delay in deployment. Some of these deployment techniques require additional components to generate a time delay or are subject to premature failure caused by harsh environments. To surmount these limitations, this research proposes a method that tailors time-delayed structural deployment that is driven by the Intermediate Axis Theorem, where rotation about the intermediate axis generates a time delay in deployment before the structure tumbles and inertial effects instigate expansion. The proposed method requires that the deployable structures have three unique principal moments of inertia in the compacted configuration. Numerical results are generated to explore the influence of the rate of rotation and geometry on time delay in structural deployment. A physical prototype demonstrates the plausibility of applying the proposed method. The results in this study encourage broader exploration of passive deployment techniques with physical time delays in deployment inspired from the Intermediate Axis Theorem.

C-Axis Aligned 3 nm Thick In2O3 Crystal Using New Liquid DBADMIn Precursor for Highly Scaled FET Beyond the Mobility-Stability Trade-off.

Oxide semiconductors (OS) are attractive materials for memory and logic device applications owing to their low off-current, high field effect mobility, and superior large-area uniformity. Recently, successful research has reported the high field-effect mobility (μFE) of crystalline OS channel transistors (above 50 cm2 V-1 s-1). However, the memory and logic device application presents challenges in mobility and stability trade-offs. Here, we propose a method for achieving high-mobility and high-stability by lowering the grain boundary effect. A DBADMIn precursor was synthesized to deposit highly c-axis-aligned C(222) crystalline 3 nm thick In2O3 films. In this study, the 250 °C deposited 3 nm thick In2O3 channel transistor exhibited high μFE of 41.12 cm2 V-1 s-1, Vth of -0.50 V, and SS of 150 mV decade-1 with superior stability of 0.16 V positive shift during PBTS at 100 °C, 3 MV cm-1 stress conditions for 3 h.

Near‐infrared light response novel shape memory actuator based on photothermal rGO‐TiO2 filler

AbstractAs an efficient method to realize photoinduced shape memory, photothermal filler has the characteristics of economy and convenience. However, the aggregation of the photothermal filler in the matrix material will reduce the material's shape memory and mechanical properties. In this work, the photothermal filler of reduced graphene oxide (rGO)‐titanium dioxide (TiO2) was prepared by the solvothermal method and then introduced into the polycaprolactone (PCL) matrices to construct a photoresponsive actuator. Because of TiO2 is uniformly loaded on the rGO surface, rGO‐TiO2 disperses well in the composites. When the GO:TiO2 ratio of photothermal filler is 1:1, the mechanical properties of PCL‐GT‐3 are the best, and the tensile strength and elongation at break are 31.8 MPa and 239.5%, respectively, and the crosslinking material under near‐infrared light has a good photothermal effect. Due to the induced difference between the in‐plane stress of the surface and the volume layer, the shape transformation can be controlled by very low energy (808 nm, 700 mW near‐infrared laser). The scheme of controlling the properties of the photoinduced shape memory material by changing only the filler type is conducive to commercial application.

The effect of organic clay on the properties of TPI/NR composite materials

TPI shape memory materials’ low flexibility and poor mechanical properties currently limit their use in a broader range of applications. Most scholars use high performance fillers to improve their mechanical properties. However, the cost of high-performance fillers is high. Therefore, the introduction of flexible natural rubber (NR) and low-cost organic clay (OC) into the trans-1,4-polyisoprene (TPI) matrix as the reinforcing phase. A new shape memory polymer— TPI/NR/OC, was prepared by mechanical melt blending.The effect of the changes of filler content on the thermodynamic properties of the composite materials were revealed by series of tests. The results showed that OC formed a homogeneous intercalation structure with the composite matrix, and OC promoted the crystallization of TPI, and part of OC was able to form physical entanglements with the molecular chains of the composites, which led to the improvement of mechanical and shape memory properties. The tensile strength of the composite at an OC dosage of 3.6phr was 19.9 MPa, with a shape fixity ratio of 97.9% and a shape recovery ratio of 96.8%. The relevant findings of this research may provide valuable design references for more areas of application of shape memory composites.