Water Induced Shape Memory and Healing Effects by Introducing Carboxymethyl Cellulose Sodium into Poly(vinyl alcohol)

Graphene Oxide-Modulated CMC/PVA Films with on-Demand Shape Recovery and Self-Healing Performance

With the advancement of artificial intelligence technologies, shape-memory polymers (SMPs) have attracted significant research interest due to their remarkable environmental responsiveness. However, conventional SMPs are limited to single-stimulus responsiveness and constrained performance, failing to meet practical application demands. This study develops a novel shape-memory carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) composite film modulated by graphene oxide (GO) with multi-stimuli responsive capabilities and water-assisted self-healing properties. The introduction of GO significantly enhances the mechanical properties, and provides efficient swelling-resistant ability and thermal conversion efficiency of the composite film, endowing it with on-demand shape-memory performance under thermal and water stimulation. It can achieve a shape fixation rate of 94.45% and a recovery rate of 97.22%. Meanwhile, the shape-memory behaviors can be precisely tailored by modulating the content of GO and PVA as well as interfacial interactions. Furthermore, the composite films achieve efficient water-triggered self-healing with a remarkable 90.6% recovery efficiency, which is attributed to their inherent hydrophilic nature and dynamic physical crosslinking architecture. This research demonstrates a novel strategy for creating stimuli-adaptive and shape-memory materials, providing a pivotal platform for their application in flexible actuation devices and intelligent medical systems.

MXene-Wood Composites: A Review of Fabrication, Properties, Applications, and Future Prospects

MXene is a cationic 2D material made of transition metal carbides known for its diverse structure and multifunctionality. It faces challenges like stacking, oxidation, and weak mechanical properties that limit its use. By integrating MXene with self-supporting porous materials, it can be stabilized and converted from fragile 2D sheets to strong 3D structures. Wood, due to its natural structure and stability, is ideal for depositing MXene, which adheres to wood via adsorption, hydrogen bonding, or reactions with wood fibers. New MXene-wood composites with improved functions have been created and show great potential for interdisciplinary research. This review covers preparation methods, applications, potential development, and challenges of MXene-wood composites, aiming to provide a research framework and progressive direction for their future development.

Foam-based antibacterial hydrogel composed of carboxymethyl cellulose/polyvinyl alcohol/cerium oxide nanoparticles for potential wound dressing

Foam-based wound dressing materials produced by dispersing gas phases in a polymeric material are soft, adapt to the body shape, and allow the absorption of wound exudate due to their porous structure. Most of these formulations are based on synthetic substances such as polyurethane. However, biopolymers have entered the field as a new player thanks to their biocompatible and sustainable nature. Incorporating biopolymers in formulations is gaining interest in scientific literature, and we extend this approach by adding antibacterial cerium oxide nanoparticles to biopolymer formulation. We introduce a novel biopolymer composite of carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and cerium oxide nanoparticles (CeO2 NPs), namely PVA-CMC@CeO2. This mixture was first foamed and then cross-linked with sodium tetraborate solution, followed by a freeze-thaw process. After the novel material's spectroscopic, structural, and morphological characterization, we investigated its swelling, drug-delivery, antibacterial, and biodegradability properties PVA-CMC@CeO2 dressing effectively inhibits Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) growth and delivers the antibiotic drug silver sulfadiazine for up to 6 h. The antibacterial properties, good swelling, and drug release profile of the blend material show promising potential in wound care applications.

4D Printing for Biomedical Applications

4D (bio-)printing endows 3D printed (bio-)materials with multiple functionalities and dynamic properties. 4D printed materials have been recently used in biomedical engineering for the design and fabrication of biomedical devices, such as stents, occluders, microneedles, smart 3D-cell engineered microenvironments, drug delivery systems, wound closures, and implantable medical devices. However, the success of 4D printing relies on the rational design of 4D printed objects, the selection of smart materials, and the availability of appropriate types of external (multi-)stimuli. Here, this work first highlights the different types of smart materials, external stimuli, and design strategies used in 4D (bio-)printing. Then, it presents a critical review of the biomedical applications of 4D printing and discusses the future directions of biomedical research in this exciting area, including in vivo tissue regeneration studies, the implementation of multiple materials with reversible shape memory behaviors, the creation of fast shape-transformation responses, the ability to operate at the microscale, untethered activation and control, and the application of (machine learning-based) modeling approaches to predict the structure-property and design-shape transformation relationships of 4D (bio)printed constructs.

Multistimuli-Responsive Shape-Memory Composites with a Water-Assisted Self-Healing Function Based on Sodium Carboxymethyl Cellulose/Poly(vinyl alcohol)/MXene

Recent advancements in artificial intelligence have propelled the development of shape-memory polymers (SMPs) with sophisticated, environment-sensitive capabilities. Despite the progress, most of the existing SMPs are limited to responding to a single stimulus and show poor functionality, which has severely hindered their future applications. Herein, we report a high-performance multistimuli-responsive shape-memory and self-healing composite film fabricated by embedding MXene nanosheets into a conventional shape-memory sodium carboxymethyl cellulose (CMC) and poly(vinyl alcohol) (PVA) matrix. The incorporation of photothermal MXene nanosheets not only enhances the composite films' mechanical strength but also provides efficient solar-thermal conversion and robust light-actuated shape-memory properties. The resultant composite films exhibit an exceptional shape-memory response to various stimuli including heat, light, and water. Meanwhile, the interfacial interactions can be modulated by adjusting the MXene content, thereby enabling precise manipulation of the shape-memory performance. Moreover, thanks to the intrinsic hydrophilicity of the components and the unique physically cross-linked network, the composite films also demonstrate an effective water-assisted self-healing capability with an impressive healing efficiency of 85.7%. This work offers insights into the development of multifunctional, multistimuli-responsive shape-memory composites, opening up new possibilities for future applications in smart technologies.

Plant-based Biomass/Polyvinyl Alcohol Gels for Flexible Sensors

Flexible sensors show great application potential in wearable electronics, human-computer interaction, medical health, bionic electronic skin and other fields. Compared with rigid sensors, hydrogel-based devices are more flexible and biocompatible and can easily fit the skin or be implanted into the body, making them more advantageous in the field of flexible electronics. In all designs, polyvinyl alcohol (PVA) series hydrogels exhibit high mechanical strength, excellent sensitivity and fatigue resistance, which make them promising candidates for flexible electronic sensing devices. This paper has reviewed the latest progress of PVA/plant-based biomass hydrogels in the construction of flexible sensor applications. We first briefly introduced representative plant biomass materials, including sodium alginate, phytic acid, starch, cellulose and lignin, and summarized their unique physical and chemical properties. After that, the design principles and performance indicators of hydrogel sensors are highlighted, and representative examples of PVA/plant-based biomass hydrogel applications in wearable electronics are illustrated. Finally, the future research is briefly prospected. We hope it can promote the research of novel green flexible sensors based on PVA/biomass hydrogel.

Mucoadhesive gellan gum-based and carboxymethyl cellulose -based hydrogels containing gemcitabine and papain for bladder cancer treatment

Local treatment of bladder cancer faces several limitations such as short residence time or low permeation through urothelium tissue. The aim of this work was to develop patient-friendly mucoadhesive gel formulations combining gemcitabine and the enzyme papain for improved intravesical chemotherapy delivery. Hydrogels based on two different polysaccharides, gellan gum and sodium carboxymethylcellulose (CMC), were prepared with either native papain or papain nanoparticles (nanopapain) to explore for the first time their use as permeability enhancers through bladder tissue. Gel formulations were characterized regarding enzyme stability, rheological behavior, retention on bladder tissue and bioadhesion, drug release properties, permeation capacity, and biocompatibility. After 90 days of storage, the enzyme loaded in the CMC gels retained up to 83.5 ± 4.9 % of its activity in the absence of the drug, and up to 78.1 ± 5.3 with gemcitabine. The gels were mucoadhesive and the enzyme papain showed mucolytic action, which resulted in resistance against washing off from the urothelium and enhanced permeability of gemcitabine in the ex vivo tissue diffusion tests. Native papain shortened lag-time tissue penetration to 0.6 h and enhanced 2-fold drug permeability All formulations demonstrated pseudoplastic behavior and no irritability. Overall, the developed formulations have potential as an upgraded alternative to intravesical therapy for bladder cancer treatment.

Highly sensitive self-healable strain biosensors based on robust transparent conductive nanocellulose nanocomposites: Relationship between percolated network and sensing mechanism

The conventional skin sensor detection of human physiological signals can be an effective method for disease diagnosis and health monitoring, but the poor biocompatibility, low sensitivity and complex design largely limit their applications. Developing natural nanofiller-reinforced composites as strain biosensors is an appealing solution to reduce environmental impacts and overcome technical bottleneck. Herein, a versatile nature skin-inspired composite film as flexible strain biosensor was developed based on cellulose nanocrystals-polyaniline (CNC-PANI) composites by utilizing their percolated conductive network in polyvinyl alcohol (PVA) matrix. The composite electronic skin showed robust mechanical strength (50.62 MPa) and high sensitivity (Gauge Factor = 11.467) with easy water-induced self-healing abilities. Moreover, we investigated the functioning mechanism of percolated network and the sensory behavior determined by CNC nanocomposite alignment. The percolation threshold of CNC-polyaniline (PANI) was determined at 4.278% and 5% CNC-PANI composite film shows the best overall sensing property. It was also discovered that the sensitivity of this type of conductive-filler electronic skin can be divided into two separate regions at different strain range due to its percolated network. With films prepared by dry casting and dip coating, the alignment of CNC-PANI also contributes to this unique change in electrical property. Generally, our results demonstrated the mechanism and tunability of conductive nanofiller-based composite strain biosensors as a potential alternative to commercial synthetic sensors.

Biodegradable shape-memory polymers and composites

Polymers have recently been making media headlines in various negative ways. To combat the negative view of those with no polymer experience, sustainable and biodegradable materials are constantly being researched. Shape-memory polymers, also known as SMPs, are a type of polymer material that is being extensively researched in the polymer industry. These SMPs can exhibit a change in shape because of an external stimulus. SMPs that are biodegradable or biocompatible are used extensively in medical applications. The use of biodegradable SMPs in the medical field has also led to research of the material in other applications. The following categories used to describe SMPs are discussed: net points, composition, stimulus, and shape-memory function. The addition of fillers or additives to the polymer matrix makes the SMP a polymer composite. Currently, biodegradable fillers are at the forefront of research because of the demand for sustainability. Common biodegradable fillers or fibers used in polymer composites are discussed in this chapter including Cordenka, hemp, and flax. Some other nonbiodegradable fillers commonly used in polymer composites are evaluated including clay, carbon nanotubes, bioactive glass, and Kevlar. The polymer and filler phase differences will be evaluated in this chapter. The recent advances in biodegradable shape-memory polymers and composites will provide a more positive perspective of the polymer industry and help to attain a more sustainable future.

A Mechanical Analysis of Chemically Stimulated Linear Shape Memory Polymer Actuation

In the present work, we study the role of programming strain (50% and 100%), end loads (0, 0.5, 1.0, and 1.5 MPa), and chemical environments (acetone, ethanol, and water) on the exploitable stroke of linear shape memory polymer (SMP) actuators made from ESTANE ETE 75DT3 (SMP‑E). Dynamic mechanical thermal analysis (DMTA) shows how the uptake of solvents results in a decrease in the glass temperature of the molecular switch component of SMP-E. A novel in situ technique allows chemically studying triggered shape recovery as a function of time. It is found that the velocity of actuation decreases in the order acetone > ethanol > water, while the exploitable strokes shows the inverse tendency and increases in the order water > ethanol > acetone. The results are interpreted on the basis of the underlying chemical (how solvents affect thermophysical properties) and micromechanical processes (the phenomenological spring dashpot model of Lethersich type rationalizes the behavior). The study provides initial data which can be used for micromechanical modeling of chemically triggered actuation of SMPs. The results are discussed in the light of underlying chemical and mechanical elementary processes, and areas in need of further work are highlighted.

Effects of Ultrasonication Time on the Properties of Polyvinyl Alcohol/Sodium Carboxymethyl Cellulose/Nano-ZnO/Multilayer Graphene Nanoplatelet Composite Films

Ultrasonication-assisted solution casting was used to prepare polyvinyl alcohol (PVA)/sodium carboxymethyl cellulose (CMC)/nano-ZnO/multilayer graphene nanoplatelet (xGnP) composite films; the performances (mechanical properties, water vapor permeability (WVP), biodegradability and antibacterial activity) of these films were investigated as a function of the ZnO NPs:xGnP mass ratio and ultrasonication time. Intermolecular interactions among ZnO NPs, xGnP and the PVA/CMC matrix were shown to improve WVP, while X-ray diffraction and scanning electron microscopy analyses revealed that the internal reticular structure of ultrasound-treated PVA/CMC/ZnO NPs/xGnP composite films was in a fluffier state than that of the untreated composite films and the PVA/CMC film. The incorporation of ZnO NPs and xGnP into the composite film reduced its tensile strength and elongation at break, and increased antibacterial activity and biodegradability. In addition, we carried out the experiment of strawberry preservation and measured weight loss ratio, firmness, content of total soluble solids and titration acid. Finally, the composite film of 7:3 had the best preservation effect on strawberries. Thus, the obtained results paved the way to develop novel biodegradable composite films with antimicrobial activity for a wide range of applications.

Ice-templating of chitosan/agarose porous composite hydrogel with adjustable water-sensitive shape memory property and multi-staged degradation performance

Water-induced shape memory polymers (SMPs) may have important applications in the fields of tissue engineering and biomedicine. However, most of the ideal candidates often suffer from non-biodegradation, weak mechanical strength and random macro-porous structure, which do limit the creativity and dynamism of water-sensitive SPMs. To address above issue, in this study, by incorporating the pH-responsive chitosan (CHIT) into a thermoplastic elastomer agarose (Agar) matrix and ice-templating, a novel dual-responsive interpenetrating polymer network hydrogel with highly porous structure was facilely prepared, which has a ultra-high porosity (>95 %) and water-induced shape recovery ratio (>90 %, response time <1 min). Results showed that such shape memory property is erasable and pH-dependent which achieves a great shape memory property at high pH and then can be erased in acidic condition. In vitro dissolution test indicates the great possibility of programming the multi-staged degradation of such composites in response to sequential pH or thermal stimuli. Based on the porous internal structure, we also demonstrate some potential applications of the hydrogels for assembly of nanomaterials, such as Au nanorods for remote sensing system and model protein of insulin for drug controlled release. Moreover, the process proved to be versatile, allowing the use of most natural polymer including gelatin, alginate, and so on. Thus, coupling of such straightforward fabrication approach, multifunctionality and biodegradable prerequisite feature indicates great potential for use in the minimally invasive surgery.

Self-Healable Conductive Nanocellulose Nanocomposites for Biocompatible Electronic Skin Sensor Systems

Electronic skins are developed for applications such as biomedical sensors, robotic prosthetics, and human-machine interactions, which raise the interest in composite materials that possess both flexibility and sensing properties. Polypyrrole-coated cellulose nanocrystals and cellulose nanofibers were prepared using iron(III) chloride (FeCl₃) oxidant, which were used to reinforce polyvinyl alcohol (PVA). The combination of weak H-bonds and iron coordination bonds and the synergistic effect of these components yielded self-healing nanocomposite films with robust mechanical strength (409% increase compared to pure PVA and high toughness up to 407.1%) and excellent adhesion (9670 times greater than its own weight) to various substrates in air and water. When damaged, the nanocomposite films displayed good mechanical (72.0-76.3%) and conductive (54.9-91.2%) recovery after a healing time of 30 min. More importantly, the flexible nanocomposites possessed high strain sensitivity under subtle strains (<48.5%) with a gauge factor (GF) of 2.52, which was relatively larger than the GF of ionic hydrogel-based skin sensors. These nanocomposite films possessed superior sensing performance for real-time monitoring of large and subtle human motions (finger bending motions, swallowing, and wrist pulse); thus, they have great potentials in health monitoring, smart flexible skin sensors. and wearable electronic devices.