Composite Memory Research Articles

Alterations of Spatial Memory and Gut Microbiota Composition in Alzheimer's Disease Triple-Transgenic Mice at 3, 6, and 9 Months of Age.

Alzheimer's disease (AD) is a progressive neurological disease. Gut microbial dysbiosis is associated with AD. This study involves the comparative assessment of spatial learning, β-amyloid peptide accumulation, and fecal microbiota alterations in 3×Tg-AD mice from 3 age groups: AD asymptomatic stage (3m), presymptomatic stage (6m), and the symptomatic stage of AD (9m). We demonstrate that spatial memory deficits, brain Aβ accumulation, and weight gain in 3×Tg-AD mice gradually appear after 6 months of age. However, the total gut bacterial counts underwent changes from 3 to 6months of age and were further altered at 9months of age. Importantly, changes in gut bacteria abundance of Desulfobacterota and Actinobacteriota phyla in 6-month-old mice preceded apparent spatial memory deficits. In summary, Changes in the gut microbial community are one of the mechanisms of early AD pathology.

Fabrication of EPDM/LDPE shape memory composites: the effect of vulcanization and crystals

Fabrication of EPDM/LDPE shape memory composites: the effect of vulcanization and crystals

Rapid-actuating high-Tg shape memory polyimide composites with synergistic “micro-nano” thermal conduction networks

Shape memory polyimide (SMPI) is one of the most promising intelligent materials and has a high potential for deformable flexible electrodes, intelligent thermal management devices, and high temperature active deployable structures, etc. In this paper, silane-modified AlN nanoparticles (M-AlN) are composited with SMPI matrix resin to prepare fast-response high-Tg shape memory composites. Besides, nano-sized AlN and micron-sized Al2O3 are used to construct “micro-nano” synergistic thermal conduction networks, in which the AlN acted as the “thermal conduction island”, and the Al2O3 acted as the “thermal conduction bridge”. The results show that the in-plane thermal conductivity of Al2O3/M-AlN/M-SMPI-2 is 5.99 W m−1K−1, compared with SMPI, its thermal conductivity increases by 91%. In addition, the shape transition temperature of Al2O3/M-AlN/M-SMPI-2 was higher than that of pure SMPI, which was at 426 °C, and the thermal response shape recovery speed is also greatly improved by 433%, which can be used in rapid-actuating and high temperature active deformation structure.

Advances in 4D printed shape memory composites and structures: Actuation and application

Advances in 4D printed shape memory composites and structures: Actuation and application

Effect of CaCO3 and compatibilizer SMA-2025 on the property of CaCO3/PLA/PBAT shape memory composites

PurposeThe purpose of this study is to improve the mechanical property and processing performance and reduce the cost of the polylacticacid/polybutyleneadipate-co-terephthalate(PLA/PBAT) composites, the calcium carbonate (CaCO3) and compatibilizer styrene-maleicanhydride copolymer (SMA-2025) were added to the PLA/PBAT system, and the effect of CaCO3 and SMA-2025 on the morphology, structure, mechanical property, thermal property, thermalstability and shape memory property of the CaCO3/PLA/PBAT composites were studied and discussed.Design/methodology/approachThe CaCO3/PLA/PBAT shape memory composites were prepared via melt-blending and hot-pressing methods, and the effect of CaCO3 and SMA-2025 on the property of the composites was investigated via scanning electron microscope, universal testing instrument, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis and DMA, respectively.FindingsThe interface property, mechanical property, thermal stability, shape memory recovery ratios and recovery stresses, and processing performance of the CaCO3/PLA/PBAT shape memory composites were significantly improved by adding of CaCO3 and SMA-2025. Moreover, the CaCO3/PLA/PBAT composites have good blowing film processing performance.Originality/valueThis study will provide a reference for the research, processing and application of the high-performance CaCO3/PLA/PBAT shape memory composites.

Effect of polybutylene adipate terephthalate on the properties of starch/polybutylene adipate terephthalate shape memory composites

In this work, the starch/polybutylene adipate terephthalate (PBAT) composite films with high starch content were prepared by hot-pressing and ultraviolet cross-linking methods using cassava starch, benzophenone (BP), degradable PBAT and citric acid as film-forming substrate, photosensitizer, toughening material and solvent, respectively. The results showed that starch and PBAT had excellent performance, resulting in the composites films exhibit robust tensile strength (9.90 MPa), decent elongation at break (500.05 %) and excellent shape memory property. Under 30 % pre-tensile strain, the shape memory fixity and recovery ratios reached 96.58 % and 93.94 %, respectively. In addition, the starch-based films were successfully rendered hydrophobic by PBAT hydrophobic characteristics. PBAT not only secures the biodegradability of the starch/PBAT composites films, but also improves the mechanical properties of them, and meets the requirements of the thermal shrinkage films when subjected to large strain.

Stiffness-tunable and self-sensing integrated soft machines based on 4D printed conductive shape memory composites

Through the synergy of nervous system and the self-regulation of muscle stiffness, living organisms are capable of quickly adjusting movements and actively adapting to dynamic environments. Likewise, the stiffness-changing and self-sensing functionalities are critical to empower soft robots with adjustable load capacity and agile movement. This work presents a paradigm for the design and fabrication of soft actuators with stiffness tunability and intrinsic self-sensing feedback through 4D printing method. The integration of 4D printed conductive composite into soft actuator body allows for stiffness adjustment within three orders of magnitude and ensures real-time stiffness-sensing, bending-sensing and pressure-sensing feedback. By constructing the theoretical deformation models and decoupling the resistance signals by machine learning methods, information on the stiffness, deformation and pressure of the material at different temperatures can be obtained. Cardiac-mimicking actuator and active therapeutic insoles are fabricated as proof-of-concept demonstrations, among which the active therapeutic insoles can perceive plantar pressure changes and conduct pressure-releasing actuation to ease the pain of patient at walk. It demonstrates the potential of this design approach for versatile applications such as medical assistive devices, artificial muscles, soft robotics, etc.

4D printing of shape memory composites with remotely controllable local deformation

Shape memory polymers with multiple temporary shapes have shown great potential for applications in biomedical, aerospace, and intelligent robotics fields. However, the realization of the multiple shape memory properties of shape memory polymers is currently mostly dependent on formula design. Here, we report a strategy to remotely program the local bending behavior of shape memory composites using an infrared light source. The infrared light source is used to locally activate a single side of the sample with a temporary shape, which induces an asymmetric shape recovery due to the temperature gradient along the thickness direction, and achieves the phototropic response on-demand bending deformation. We exerted control over the bending deformation of the composite prototypes by devising the 3D printing parameters, infrared light intensity, and temporary shape programming. As a demonstration case, we designed and prepared a hand-like structure that can be bent sequentially, a flower whose petals can be excited to fold sequentially, and a digital logic circuit for sequential lighting of LEDs.

Plasma biomarkers identify older adults at risk of Alzheimer's disease and related dementias in a real-world population-based cohort.

Plasma biomarkers-cost effective, non-invasive indicators of Alzheimer's disease (AD) and related disorders (ADRD)-have largely been studied in clinical research settings. Here, we examined plasma biomarker profiles and their associated factors in a population-based cohort to determine whether they could identify an at-risk group, independently of brain and cerebrospinal fluid biomarkers. We measured plasma phosphorylated tau181 (p-tau181), neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), and amyloid beta (Aβ)42/40 ratio in 847 participants from a population-based cohort in southwestern Pennsylvania. K-medoids clustering identified two distinct plasma Aβ42/40 modes, further categorizable into three biomarker profile groups: normal, uncertain, and abnormal. In different groups, plasma p-tau181, NfL, and GFAP were inversely correlated with Aβ42/40, Clinical Dementia Rating, and memory composite score, with the strongest associations in the abnormal group. Abnormal plasma Aβ42/40 ratio identified older adult groups with lower memory scores, higher dementia risks, and higher ADRD biomarker levels, with potential implications for population screening. Population-based plasma biomarker studies are lacking, particularly in cohorts without cerebrospinal fluid or neuroimaging data. In the Monongahela-Youghiogheny Healthy Aging Team study (n=847), plasma biomarkers associated with worse memory and Clinical Dementia Rating (CDR), apolipoprotein E ε4, and greater age. Plasma amyloid beta (Aβ)42/40 ratio levels allowed clustering participants into abnormal, uncertain, and normal groups. Plasma Aβ42/40 correlated differently with neurofilament light chain, glial fibrillary acidic protein, phosphorylated tau181, memory composite, and CDR in each group. Plasma biomarkers can enable relatively affordable and non-invasive community screening for evidence of Alzheimer's disease and related disorders pathophysiology.

Development of Ti–26Nb–1.2TiC shape memory composite for biomedical applications

Ti–Nb alloys have great potential in biomedical applications as bone-implant materials due to their low elastic modulus, superelasticity, high corrosion resistance, and good biocompatibility. However, the low yield strength and poor superelasticity of Ti–Nb alloys restrict their practical clinical applications. Here, we report the mechanical properties and superelasticity, corrosion behavior, and biocompatibility of a Ti–26 at.% Nb–1.2 vol.% TiC (Ti–26Nb–1.2TiC) shape memory composite (SMC) prepared by vacuum arc melting and hot rolling. The yield strength, critical stress for inducing martensitic transformation, and elongation of the Ti–26Nb–1.2TiC SMC and a Ti–26Nb alloy were 460 and 337 MPa, 251 and 115 MPa, and 27.2% and 24.1%, respectively. The recovery rate of the SMC under 4% pre-strain reached 91.4%, which was 1.2 times that of the Ti–26Nb. Electrochemical tests in Hanks’ solution revealed that the corrosion current density, passive current density, and corrosion rate of the SMC were lower than those of the Ti–26Nb. Both the Ti–26Nb alloy and Ti–26Nb–1.2TiC SMC showed good cell viability with grade 0 cytotoxicity in relation to MG-63 osteosarcoma cells.

Development of cyanate ester‐based shape memory composite reinforced by multi‐walled carbon nanotube modified with silicon dioxide

AbstractCyanate ester‐based shape memory composites with superior mechanical properties and good shape memory performance are needed in the aerospace field. In this work, we utilized a simple sol–gel method to fabricate multi‐walled carbon nanotubes coated with silica (MWCNT@SiO2), which were used to construct a cyanate ester‐based shape memory composite (SMPC). The moisture resistance of SMPC was improved by the introduction of MWCNT@SiO2. MWCNT@SiO2 had an efficient enhancement effect on the mechanical strength and toughness of SMPC, and the SMPC exhibited the best mechanical properties with 0.9 wt% loading of MWCNT@SiO2, which was associated with the dispersion of MWCNT@SiO2 in the resin matrix. Compared to neat cyanate ester and epoxidized hydroxyl‐terminated polybutadiene resin matrix, it was found that the storage modulus of SMPC increased and the values of glass transition temperatures decreased by incorporation of MWCNT@SiO2. Meanwhile, the SMPC retained good shape memory performance, corresponding to high shape fixity ratio and shape recovery ratio (over 98% after 10 test cycles). The addition of MWCNT@SiO2 accelerated the shape memory progress of SMPC.

Longitudinal associations of anticholinergic medications on cognition and possible mitigating role of physical activity.

Many older adults take at least one prescription medication with anticholinergic (ACH) activity, which can impact the central nervous system and can lead to cognitive decline and impairment especially in an aging population susceptible to cognitive changes. We examined this relationship between ACH burden and cognitive function in middle-aged and older adults. We further determined if increased activity levels mitigated the relationships between ACH burden and cognition. Data from The Reasons for Geographic and Racial Differences in Stroke project were used. We included 20,575 adults aged ≥45 years with longitudinal cognitive testing. The anticholinergic cognitive burden (ACB) scale was used to assess for ACH use and overall burden. Cognitive data included an overall composite score, a memory, and verbal fluency composites. Mixed effects models were conducted to determine if cognitive function worsened over time for participants with higher ACB (>3) scores. The full model adjusted for age, sex, race, education, diabetes, hypertension, cardiovascular disease, congestive heart failure, and dyslipidemia, self-reported physical activity (PA) and depressive symptoms. A significant relationship between ACH burden and composite cognitive scores was found (p= <0.001), with those with higher ACB showing more rapid cognitive decline over time. There was an effect of age for participants with higher ACB (>3) scores and ACB as a continuous variable. Baseline PA level was associated with less cognitive decline over time and this effect was greater in older cohorts. We observed an effect of ACHs on cognition in adults ≥45 years old that worsened with age. ACH users showed more cognitive effects, whereas PA emerged as a possible mitigating factor.

Programmable shape memory bismaleimide composite claw with two-way grabbing function

• A series of shape memory polymers (SMPs) based on bismaleimide (BMI) were synthesized. The BMI-based polymers are made of a 4,4'-bismaleimidodiphenylmethane (BDM) matrix and chain extender polyether diamine poly(propyleneglycol) bis(2-aminopropylether) (D400). Then crosslinking agent 2,4-tolylene diisocyanate (TDI) was added to form a crosslinking network. Last, it was toughened by adding liquid nitrile rubber (ETBN). • These BMI-based SMPs achieved wide T g ranges of 170-200 °C. This property allows these SMPs to remember two pre-deformed shapes. By designing the second pre-deformed shape similar to the original shape, the 2W-SME can be achieved. • Carbon fabric reinforced BMI-based shape memory composites (SMPCs) were prepared. By exploring the preparation process, the claw structure was formed with this BMI-based SMPC. The composite claw realizes the motion of reach out and grab 250g items. Functional polymer materials with a two-way shape memory effect (2W-SME) have attracted great interest recently. Herein, by introducing 2,4-tolylene diisocyanate (TDI) into the bismaleimide (BMI) network, the shape memory polymers we synthesized are a series thermosetting polymers with adjustable T g and triple-shape memory effect(triple-SME), and realized two-way behavior by programming. Those shape memory polymers (SMPs) were toughened by acrylonitrile-butadienerubber (ETBN) and reinforced with carbon fabric to make composites. The cured network with varying transition temperatures and flexibility was synthesized by varying the cyanate ester and rubber concentration in the system. Polymers with a broad glass transition temperature ( T g ) range can achieve triple-SME. Due to the complex cross-linked structure, the two-way behavior demonstrated above for BMI-based SMPs stem from its broad T g ranges. Select two temperatures higher and lower than T g as the switching temperature, and fix the pre-deformed shape in the opposite direction at these two temperatures to achieve the two-way behavior. These BMI-based SMPs could grab objects through the design of the structure. Results indicated that the above BMI-based SMPs with two-way function have excellent thermal stability and mechanical properties, which provides the basic attempts for the further development of thermosetting SMPs and their composite materials.

Bionic Shape Memory Polyurethane/Prussian Blue Nanoparticle-Based Actuators with Two-Way and Programmable Light-Driven Motions

A bionic smart actuator that can imitate types of biological motions plays a vital role in intelligent systems, which therefore becomes one of the hottest development directions in recent years and has attracted more and more attention from researchers. In this study, a kind of near-infrared (NIR) light-responsive shape memory polyurethane SMPU-PB is developed by doping the citric acid-modified Prussian blue nanoparticles. Based on it, a bionic “athlete” has performed repeatable photomechanical jumping behavior to cross obstacles under 808 nm NIR light irradiation. Furthermore, through the integration of SMPU-PB with pre-strained UV-responsive polyurethane film, a hybrid wavelength-selective responsive structure capable of reversible, programmable, and controllable motions is produced. By using the two-way light-driven shape memory composite, the bionic actuator is able to complete a series of tasks including accurate bending and mechanical gripping.

Magnetofriction—a new concept for shape memory composites

This paper introduces a new concept for shape memory based on elastic forces and magnetically induced friction forces in composite materials consisting of magnetoactive elastomers (MAEs). Magnetic attraction forces between two MAEs generate a contact pressure at their interface and the friction allows to maintain stable deformed shapes of the so-called magnetofriction shape memory polymers (MF-SMPs). When the contact is loosened, the friction forces vanish and the elastic forces in each part of the assembly bring the parts back into their initial state where the contact can be established once again. The shape memory effect is studied in three-point bending tests with two stacked MAEs. The global force-displacement relations reveal a hysteretic behavior due to local residual displacements after the test are observed by the help of digital image correlation. The test structure stores up to 25% of the applied displacement. The local contact state (sliding or sticking) is evaluated in different regions of the MF-SMP which gives an insight into the shape memory mechanism magnetofriction. Two methods for the shape-recovery of the MF-SMP by elastic forces in the MAEs are proposed, a manual separation and an air flow at the interface of the MF-SMP, and a comparison of magnetofriction to other shape memory mechanisms is performed.

3D Printing photo-induced lignin nanotubes/polyurethane shape memory composite

The excellent flexibility, biocompatibility, and shape memory properties of polyurethane (PU) have attracted great attention to fabricate devices for application in the fields of electronics and biomedical, etc. However, it still consists a challenge to fabricate shape memory polymer (SMP) materials with complicated shapes in response to remote stimuli precisely and instantly. In this paper, we achieved ultraviolet light responsive SMP composites by direct ink writing (DIW) 3D printing shape memory polyurethane (SMPU) with introduction of the laboratory prepared lignin nanotube (LNT) as UV absorbent. We prepared lignin nanotube with uniform morphology by dissolving and then controllable molecular assembling way during dialysis in deionized water. The 3D printed SMP composite of PU/LNT was found to reach the shape recovery rate of 99% under UV radiation (370 nm) for 15 min. In addition, the tensile strength of the 3D printed SMP composite of PU/LNT is increased to 16.4 MPa, which is 131% higher than that of the pristine PU (7.11 MPa). It is worth noting that the glass transition temperature (Tg) of the 3D printed SMP composite of PU/LNT changed steadily from 47 °C to 33 °C by increasing the LNT content to 9%, which endows the composites with much wider application feasibility. The exploration on photo responsive 3D printed SMP composites with accurate shape recovery rate provides new candidates to improve the development of biomaterials and intelligent robots.

Dual thermal/electrical-driven compressive recovery behaviors of 3D braided shape memory composite tubes

3D braided shape memory composite (SMPC) tubes have great potential in designing smart structural components because of high inertia moment and near-net shape manufacturing. Here we developed a 3D braided carbon fiber reinforced shape memory polyurethane-based composite tube and investigated their thermal/electrical shape memory behaviors subjected to compression. The radial and axial compressive behaviors, thermally-electrically shape memory behaviors, and shape recovery forces of the SMPC tubes with different braiding angles were analyzed. The out-of-plane displacement and temperature field were obtained with 3D digital image correlation (DIC) and infrared thermography to characterize transverse compression deformation. We found that the 60° sample had the highest recovery force compared to the other braided angle samples, while the shape recovery speed was lower than small-angle samples. In the transverse compressive electro-thermal recovery test, the 30° sample reaches to glass transition temperature faster at the same voltage, and the 45° sample exhibits maximum shape recovery speed. The 3D braided SMPC tubes exhibited excellent electro-thermal shape memory behaviors and high recovery force, which were expected to extend the application of smart actuators.

Preparation of PLA-TPU-Nanoclay composites and characterization of their morphological, mechanical, and shape memory properties

In this study, a combination of polylactic acid polymer and thermoplastic polyurethane with the addition of nano-clay particles was used. The reason for using clay nanoparticles and their strength is the low price and availability of this material. Adding nano-clay particles to the polymer composition improves the mechanical properties of the composite as they will interact with functional groups of the polymer.The results of the FTIR spectroscopy confirmed the presence of three components in the compound indicating that no chemical reactions occurred among the three components during the compounding process. The FE-SEM images taken from the compounds showed that TPU and nano-clay particles were evenly distributed in the PLA matrix. The DMTA results were utilized to determine the transfer temperature of the compounds as well as the storage and loss modulus and the shape memory properties. The XRD spectroscopy was used to determine the crystallinity and exfoliation of the nanoparticles. The mechanical properties of the fabricated polymer compounds were determined. It was found that the sample with 3% by weight of clay nanoparticles had the highest strength, and the sample with 5 wt% of clay nanoparticles had the highest toughness among nanocomposites. According to the hardness measurement, the sample with 5% by weight of clay nanoparticles has the highest hardness amongst all prepared composites. The memory properties of the prepared nanocomposites showed a significant improvement with increasing the amount of nanoparticles.This study showed the suitability and efficiency of PLA, TPU, and clay nanoparticle melt mixing methods in achieving a relatively tough shape memory composite. At the same time, this method is also inexpensive and scalable.

Bio‐Inspired Semi‐Active Safeguarding Design with Enhanced Impact Resistance via Shape Memory Effect

AbstractInspired by creatures reducing impact damage, a novel semi‐active protection strategy to enhance impact resistance through structural adjustment is proposed. The heat‐activated shape memory composites (PCLE) consisting of polycaprolactone (PCL) and shear stiffening elastomer are first prepared. The PCLE with 50 wt.% PCL (PCLE‐50%) presents tensile strength of 0.46 MPa, fracture strain of 148%, high shape fixity and recovery rates (97.9% and 91.1%), and stable shape‐memory repeatability. Furthermore, various PCLE‐50%‐based structures are fabricated, which show reinforced anti‐impact performance after shape‐shifting. Loading from 300 mm, the maximum drop hammer impact force of no protection, PCLE‐50%, and deformed assembled single‐branch structure are 3.98 kN, 1.75 kN, and 0.93 kN, respectively. Additionally, assembled complex structures also exhibit exceptional energy absorption properties. Ultimately, intelligent clothing is successfully manufactured. Besides good anti‐impact effect, the clothing shows excellent thermal insulation capabilities whose surface temperature is 31.7 °C after heating for 600 s at 42 °C. This study provides an innovative means to develop deformable, wearable, and intelligent protective devices.

Identification of a Hypoxia-Related Signature as Candidate Detector for Schizophrenia Based on Genome-Wide Gene Expression

Introduction: Schizophrenia (SCZ), a severe neuropsychiatric disorder with high genetic susceptibility, has high rates of misdiagnosis due to the unavoidably subjective factors and heterogeneous clinical presentations. Hypoxia has been identified as an importantly risk factor that participates in the development of SCZ. Therefore, development of a hypoxia-related biomarker for SCZ diagnosis is promising. Therefore, we dedicated to develop a biomarker that could contribute to distinguishing healthy controls and SCZ patients. Methods: GSE17612, GSE21935, and GSE53987 datasets, consisting of 97 control samples and 99 SCZ samples, were involved in our study. The hypoxia score was calculated based on the single-sample gene-set enrichment analysis using the hypoxia-related differentially expressed genes to quantify the expression levels of these genes for each SCZ patient. Patients in high-score groups were defined if their hypoxia score was in the upper half of all hypoxia scores and patients in low-score groups if their hypoxia score was in the lower half. GSEA was applied to detect the functional pathway of these differently expressed genes. CIBERSORT algorithm was utilized to evaluate the tumor-infiltrating immune cells of SCZ patients. Results: In this study, we developed and validated a biomarker consisting of 12 hypoxia-related genes that could distinguish healthy controls and SCZ patients robustly. We found that the metabolism reprogramming might be activated in the patient with high hypoxia score. Finally, CIBERSORT analysis illustrated that lower composition of naive B cells and higher composition of memory B cells might be observed in low-score groups of SCZ patients. Conclusion: These findings revealed that the hypoxia-related signature was acceptable as a detector for SCZ, providing further insight into effective diagnosis and treatment strategies for SCZ.