18 - Electrospun shape-memory polymer fibers and their applications

Electrospun poly (ɛ-caprolactone)/silk fibroin core-sheath nanofibers and their potential applications in tissue engineering and drug release

Tissue engineering (TE) is a modern approach to improve or restore tissues that has been diseased or damaged by combining the factors in growth signaling and appropriate cells to form compatible biomaterial scaffold. Bone repair has been a major global health challenge in recent decades. Bone transplantation is widely used as an effective clinical treatment for this purpose. However, there are several serious issues with transplantation, including a shortage of autologous bone, immune rejection, the risk of virus transmission with allogeneic bone, and postoperative complications. In recent years, scaffolds for bone tissue engineering have emerged as a promising alternative for bone repair. These scaffolds have porous structures that mimic the extracellular matrix, which can enhance the migration, proliferation, and differentiation of osteoblasts. This process accelerates the repair of bone defects.The usage of bioactive materials has become important tool in tissue engineering and regenerative medicine application as they are to mimic tissues mechanically, chemically, and physically. Polymeric scaffold provides numerous advantageous for tissue engineering since the physicochemical properties such as porosity, pore size, solubility and biocompatibility can be controlled. Therefore, research works were carried out to explore the potential of various materials in producing bone scaffolds in tissue engineering technology. As for both newcomers and experts, this review paper will help them to find information on various types of biomaterials in imparting or enhancing their biological properties such as biocompatibility, bacterial inhibition, tissue regeneration and cell growth, bio inertness, bioactive and resorbability for bone scaffold tissue engineering application.

Shape memory polymers (SMPs) have the capacity of memorizing a temporary shape and recovering their initial shape in response to various external stimuli. As one of promising class of intelligent materials, it has attracted great attention because of its potential applications in many areas, such as biomaterials and biotechnology, automotive industry, and aerospace field. Aliphatic polymers play an important role in the molecular design of SMPs owing to its excellent biodegradability and biocompatibility, and suitable thermal transition temperature range. This review focuses on the recent progress of shape memory polymers based on the aliphatic polyesters such as poly(lactic acid) (PLA), poly ( p -dioxanone) (PPDO), poly(butylene succinate) (PBS), poly( ω -pentadecalactone) (PPDL) and poly( ɛ -caprolactone) (PCL) and so on. From the view of architecture design, different systems are classified by block copolymers, crosslinking networks and interpenetrating networks. The influence of architectural features on the shape memory behaviors is also discussed. The block copolymers have been identified a typical mature system in design of dual-shape material, and the crystalline aliphatic polyesters can be served as the netpiont or the molecular switch in a SMP, depending on its transition temperature range among the binary systems. The thermoplastic feature of block copolymers endows an easy processibility. The various architectures of crosslinking network meet the increasing demand of SMPs design. Constructing network with crystallizable polyester segment such as PCL may achieve SMPs in one-way and two-way mode, and the stress-free two-way mode can also be realized by an elaborate architecture with pre-programed treatment. Embedding two segments in one network may achieve a triple-shape memory effect, meanwhile, incorporating two segments in an interpenetrating polymer network may result in a triple-shape material with improved performance. Recently, the SMPs based on dynamic networks become the new trend, which may combine the self-healing with shape memory effect in one system, and both dynamic covalent bond and non-covalent bond have been concerned. In order to fulfill the increasing requirement of application, the SMPs with multi-shape memory effect, multi-responsibility and multi-functionality are highly expected.

Shape memory polymers (SMPs) are a new member of the smart materials family. SMPs have found wide applications or potential applications in almost all manmade structures and devices. In order to better design smart structures and devices using SMPs, thermomechanical constitutive modeling is essential. In this insight paper, we will focus on presenting several multi-length-scale and multi-physics modeling frameworks, including the thermodynamics consistent model, elasto-viscoplastic model, statistical mechanics model, and phase evaluation law model. The SMPs modeled will include amorphous one-way shape memory polymers, semicrystalline one-way shape memory polymers, semicrystalline two-way shape memory polymers, and functional and mechanical damage effects on SMPs. Finally, we will give some in-depth perspectives on future development in this area of study.

Development of HAp Reinforced Biodegradable Porous Structure Through Polymer Deposition Technology for Tissue Engineering Applications

The European Union draft Waste Electrical and Electronic Equipment (WEEE) directive calls for the removal and separate treatment of liquid crystal displays (LCD). This aspect of the legislation will potentially have an important impact upon the future `End of Life' (EoL) processing of much WEEE. Active Disassembly using Smart Materials (ADSM) has been proven to have applicability in self-dismantling, nondestructive and rapid disassembly of small electronic products. This paper investigates the technical feasibility of removing LCD screens from IT communication products using ASDM technology. In this paper an option is suggested to cleanly separate LCD screens from printed circuit boards, utilizing an LCD bracket made from `shape memory polymer'. The case study products employed are Nokia Japanese J-Phones. Demonstration experiments with initial results are presented, and future developments discussed. SMB glass transformation temperatures (Tg) and time efficiency in disassembly are considered.

Shape memory polymers (SMPs) are known as smart polymer materials which can be deformed and fixed in a temporary shape and can recover to its original shape upon an external stimulus such as temperature which is the main stimulus for general SMPs. In this research, a renewable natural resource based on vanillin-furfurylamine benzoxazine (V-fa) and eugenol-furfurylamine benzoxazine (E-fa) are developed to substitute the use of petroleum based polybenzoxazine. The as-synthesized V-fa and E-fa show the degradation temperature at 5% weight loss to be as high as 343 and 310?C and char content to be 66 and 54%, respectively. Effects of epoxidized castor oil (ECO) content at 10-50wt% filled in bio-based polybenzoxazine on thermal, mechanical and shape memory properties of bio-based polybenzoxazine/bio-based epoxy SMPs are thoroughly investigated. The results reveal that with increase in ECO content, storage modulus and glass transition temperature of V-fa/ECO and E-fa/ECO copolymer decreased providing the values of 2.27 GPa to 1.60 GPa and 158?C to 100?C, respectively for V-fa/ECO copolymer and 1.53 GPa to 1.16 GPa and 40?C to -17?C, respectively for E-fa/ECO copolymer. In shape memory properties, the V-fa/ECO SMPs show shape fixity values at a room temperature of 86-94% and the values decrease with increasing ECO content, while the temporary shape at room temperature of the E-fa/ECO SMPs cannot fixed. Additionally, the V-fa/ECO SMPs provided the shape recovery values at Tg+20?C of 81-96% and the values increase with increasing of ECO content. Furthermore, it was observed that the V-fa/ECO copolymer having 40wt% of V-fa content exhibits good balance properties between shape memory performance and thermomechanical properties and it can be greatly recovered to the original shape for 5 cycles.

Stimuli-responsive materials are smart materials capable to adjust their properties (e.g. shape and size) in response to an external or internal stimulus including temperature, light, magnetic field, mechanical stress, and pH. Shape memory polymers (SMPs) are attractive class of stimuli-responsive, programmable smart materials with shape-memory behavior: memorize their original, permanent shape; deform and fix into a secondary, temporary shape; and recover the original, permanent shape upon applying an external stimulus. In recent years, advancing intelligent supercapacitors and batteries have attracted significant attention whereas stimuli-responsive materials were integrated to induce stimuli-responsive properties to introduce new properties or mitigate some of the existing issues such as thermal management, mitigating volume change-induced performance degradation, recovery from a mechanical deformation, self-healing, electrochromism. Indeed, integrating energy storage technologies with a variety of stimuli are a fascinating method to realize smart functions [1-3].Herein, we aim to develop a heat-responsive battery capable of mitigating the impact of incidental mechanical abuse or deformation. To achieve this, a shape-memory solid polymer electrolyte (SMSPE) is engineered and incorporated into lithium metal batteries (LMBs). In response to an external heat, the engineered SMSPEs recover their original shape and size from mechanical deformations such as bending and elongation. This study opens-up a promising approach for engineering intelligent batteries responsive to unfavorable internal or external stimuluses, with potential to have a broad impact on other energy storage technologies in different sizes and shapes. The Li|SPSPEs|LFP full cell batteries display a long-term cycle life with a discharge capacity of ~120 mAh g−1 at C/10 in ambient temperature with around 90% capacity retention after 100 cycles. Moreover, the Li|SPSPEs|Li symmetrical cells exhibit a long-term stability with a low voltage polarization at a current density of 0.05 mAh cm−2 for up to 1000 cycles.Overall, the proposed approach shows a promising design principle which can open up new possibilities for the next-generation batteries and their safe operation. With vast range of available SMPs with tunable chemistries, transition temperatures, and high shape-memory performance, and opens up new frameworks to address a variety of detrimental, unresolved issues such as thermal runaway, with potential expansion to the other energy storage technologies.

The present work describes the preparation of nanocomposites based on chitosan (QS)/copper nanoparticles (nCu) with antibacterial properties and potential application in tissue engineering. For this purpose, nanocomposites were prepared by solution blending with ultrasound assisted, aiming to increase the nanoparticles dispersion in the biopolymer. FTIR analyses demonstrates that nCu supported in QS increase their interaction of nanoparticles with amine/hydroxyl groups of QS molecule. UV-Vis analyses demonstrates that QS/nCu nanocomposites have an absorption signal associated with the presence of nanoparticles and the possible Cu2+ ions release in liquid media. AFM analyses shown that hydrated QS form a mesh with micro pores, improving the bacterial penetration and the direct contact with nCu. This behavior was corroborated by antibacterial assays, where QS/nCu nanocomposites shown an antibacterial activity higher than 90% between 90-180 minutes of interaction. Our results suggest that is possible to obtain combined antibacterial/biocompatible nanomaterials with potential application in tissue engineering.

Jewelry is a passion of a large segment of children, especially females, which inspires the jewelry designer to direct this passion to raise a generation of young jewelry designers, using the combination of the arts of jewelry design and formulation and the science of smart materials. Smart materials are one of the most important fruits of technological development, and they vary between shape memory materials, color-changing materials, light-sensitive materials, and others sensitive to electricity. Given that jewelry design is one of the most important fields that affect the culture and thinking of the recipient, and based on the major role of shaping processes in enriching jewelry design, the interest in this research was in studying smart materials as a result of advanced technological developments and the possibility of employing them in simulating some jewelry shaping processes, so that this simulation would be the nucleus of a project to raise the young designer. The problem of the research is the scarcity of the use of smart materials in children's jewelry, and the lack of diversity of shaping methods in jewelry crafting collections directed at children. The research aims to build a knowledge base about smart materials, and employ these materials in simulating jewelry shaping processes. The importance of the research lies in its attempt to benefit from smart materials as a result of advanced technological developments in simulating some jewelry forming processes, with the aim of raising the child practicing this simulation as a young designer. Through the descriptive analytical approach, the research concluded that there are multiple types of smart materials, including shape memory materials, color changing materials, and materials sensitive to pressure and electricity. Through the experimental approach, the research concluded that some smart materials can be developed to suit children's practices. Main Results: 1-.sing smart materials to simulate some jewelry formation processes. 2. Using smart materials leads to diversifying the forming methods in jewelry collections directed at children. 3. Shape memory polymer can be employed to simulate the process of forming ceramic jewelry. 4. Simulating the process of forming jewelry with wires using nitinol wires. 5. Simulating the process of inlaying jewelry with micromosaics using glow-in-the-dark lobes and (UV Resin) 6. The possibility of simulating the process of thermal forming glass jewelry through luminous thermal beads 7. Employing smart materials to simulate some jewelry forming processes makes them suitable for children's practices in middle childhood. 8. The high flexibility of nitinol wires weakens the stability of their formations. 9. Developing nitinol wire by combining it with another aluminum wire of the same thickness. 10. Nitinol wires combined with colored aluminum wires have an attractive surface appearance for children in addition to the ability to stabilize the formation.

Stimuli-responsive chitosan (CS) hydrogels exhibit great potential for drug delivery and tissue engineering; however, the structure of these stimuli-responsive CS hydrogels, such as dual pH- and thermo-responsive hydrogels, is difficult to control or needs additional crosslinking agents. Here, a new dual pH- and thermo-responsive hydrogel system is developed by combining pH-responsive C6 -OH allyl-modified CS (OAL-CS) with thermo-responsive poly(N-isopropylacrylamide) (PNIPAM). The thiol groups in PNIPAM and the allyl groups in OAL-CS can rapidly form crosslinking hydrogel network by "thiol-ene" click chemistry under UV irradiation. As expected, the swelling ratio of the OAL-CS/PNIPAM hydrogel can be controlled by changing pH and temperature. Moreover, the hydrogel displays non-cytotoxic nature toward human bone marrow mesenchymal stem cells, and the histological analyses reveal the subcutaneous tissue with no signs of inflammation after 5 days of injection in vivo. The results indicate that the new OAL-CS/PNIPAM hydrogel has potential to serve as a smart injectable platform for application in drug delivery and tissue engineering.

Shape memory polymers (SMPs) have emerged as a revolutionary class of smart materials with enormous potential for applications in engineering and science. This manuscript provides a comprehensive review, examining their processing techniques, compositions, characteristics, and applications. It also looks at different shape memory polymer materials, blends, and composites in a critical way by looking at their features and improved mechanical, thermal, electrical, and other properties. It discusses all reinforcements, such as carbon nanotubes, graphene, and metal nanoparticles, used in earlier studies and their impact on various shape memory composites and their properties. Recent trends in research related to shape memory polymer composites (SMPCs) have focused on providing solutions to these problems by adding fillers or reinforcements and/or combining them with other polymers. Further, it provides major applications of SMPS in biomedical, aerospace, smart textiles, sensors, and self-healing materials. A detailed review of all these applications, along with their challenges also discussed thoroughly. This review helps in providing a bridge between existing knowledge and future directions of SMPs and composites involve developing multi-stimuli responsive materials, improving material properties using hybrid reinforcements, developing complex shape recovery mechanisms, including self-healing and functional futures in emerging areas like biomedical, soft robotics, and other applications.

ABSTRACTIn the field of smart materials, an increasing demand is being observed for shape memory materials that exhibit advanced stimuli‐sensing and responsive capabilities. Two‐way shape memory polymers (2 W‐SMPs), as a novel type of smart shape memory material, offer numerous advantages over traditional one‐way shape memory polymers (1 W‐SMPs), particularly the fully reversible shape memory effect (SME), where the two‐way process (low‐temperature shape fixation and high‐temperature recovery to the original shape) occurs without the need for external energy input. These polymers are lightweight and exhibit remarkable deformation abilities, reversible changes in modulus, and multiple actuation modes. Additionally, they feature a high elastic modulus and increased response stress, making them particularly suitable and indispensable in fields ranging from medical devices and robotics to aerospace engineering and smart textiles. This review focuses on 2 W‐SMPs, detailing the underlying mechanisms of both 1 W‐SMPs and 2 W‐SMPs, as well as the various driving modes. We further discuss quasi‐2 W‐SMPs (with applied load force σ ≠ 0) and 2 W‐SMPs (with applied load force σ = 0) across different cross‐linking strategies. It also covers the broad applications of SMP materials and outlines the current challenges and potential avenues for future research.

In recent years, smart materials have piqued the interest of scientists and physicians in the biomedical community owing to their ability to modify their properties in response to an external stimulation or changes in their surroundings. Biocompatible piezoelectric materials are an interesting group of smart materials due to their ability to produce electrical charges without an external power source. Electric signals produced by piezoelectric scaffolds can renew and regenerate tissues through special pathways like that found in the extracellular matrix. This review summarizes the piezoelectric phenomenon, piezoelectric effects generated within biological tissues, piezoelectric biomaterials, and their applications in tissue engineering and their use as biosensors.

Chapter 14 reviews shape memory polymers (SMPs). Shape memory polymers belong to the family of shape memory materials (SMMs), which can be deformed into a predetermined shape under some imposed specific conditions such as temperature, electric or magnetic field, as well as strain and stress. These shapes can be relaxed back to their original field-free shapes under thermal, electrical, magnetic, strain, stress, temperature, laser, or environmental stimuli. These transformations are essentially due to the elastic energy stored in SMMs during initial deformation. As a member of SMMs, SMPs are stimuli-sensitive polymers. Shape memory polymers normally use either heat or laser light energy as a stimulant to change shape. The thermally-induced shape memory effect can be observed by irradiation with infrared light, exposure to alternating magnetic fields, application of an electric field or immersion in water.