Systematic Development Strategy for Smart Devices Based on Shape-Memory Polymers

Application of 4D printing and bioprinting in cardiovascular tissue engineering

Cardiovascular diseases have remained the leading cause of death worldwide for the past 20 years. The current clinical therapeutic measures, including bypass surgery, stent implantation and pharmacotherapy, are not enough to repair the massive loss of cardiomyocytes after myocardial ischemia. Timely replenishment with functional myocardial tissue via biomedical engineering is the most direct and effective means to improve the prognosis and survival rate of patients. It is widely recognized that 4D printing technology introduces an additional dimension of time in comparison with traditional 3D printing. Additionally, in the context of 4D bioprinting, both the printed material and the resulting product are designed to be biocompatible, which will be the mainstream of bioprinting in the future. Thus, this review focuses on the application of 4D bioprinting in cardiovascular diseases, discusses the bottleneck of the development of 4D bioprinting, and finally looks forward to the future direction and prospect of this revolutionary technology.

Harnessing 4D Printing Bioscaffolds for Advanced Orthopedics

The development of programmable functional biomaterials makes 4D printing add a new dimension, time (t), based on 3D structures (x, y, z), therefore, 4D printed constructs could transform their morphology or function over time in response to environmental stimuli. Nowadays, highly efficient bone defect repair remains challenging in clinics. Combining programmable biomaterials, living cells, and bioactive factors, 4D bioprinting provides greater potential for constructing dynamic, personalized, and precise bone tissue engineering scaffolds by complex structure formation and functional maturation. Therefore, 4D bioprinting has been regarded as the next generation of bone repair technology. This review focuses on 4D printing and its advantages in orthopedics. The applications of different smart biomaterials and 4D printing strategies are briefly introduced. Furthermore, one summarizes the recent advancements of 4D printing in bone tissue engineering, uncovering the addressed and unaddressed medical requirements. In addition, current challenges and future perspectives are further discussed, which will offer more inspiration about the clinical transformation of this emerging 4D bioprinting technology in bone regeneration.

Carbon-Based Materials for Articular Tissue Engineering: From Innovative Scaffolding Materials toward Engineered Living Carbon

Carbon materials constitute a growing family of high-performance materials immersed in ongoing scientific technological revolutions. Their biochemical properties are interesting for a wide set of healthcare applications and their biomechanical performance, which can be modulated to mimic most human tissues, make them remarkable candidates for tissue repair and regeneration, especially for articular problems and osteochondral defects involving diverse tissues with very different morphologies and properties. However, more systematic approaches to the engineering design of carbon-based cell niches and scaffolds are needed and relevant challenges should still be overcome through extensive and collaborative research. In consequence, this study presents a comprehensive description of carbon materials and an explanation of their benefits for regenerative medicine, focusing on their rising impact in the area of osteochondral and articular repair and regeneration. Once the state-of-the-art is illustrated, innovative design and fabrication strategies for artificially recreating the cellular microenvironment within complex articular structures are discussed. Together with these modern design and fabrication approaches, current challenges, and research trends for reaching patients and creating social and economic impacts are examined. In a closing perspective, the engineering of living carbon materials is also presented for the first time and the related fundamental breakthroughs ahead are clarified.

Development of Trans-1,4-Polyisoprene Shape-Memory Polymer Composites Reinforced with Carbon Nanotubes Modified by Polydopamine

In this study, which was inspired by mussel-biomimetic bonding research, carbon nanotubes (CNTs) were interfacially modified with polydopamine (PDA) to prepare a novel nano-filler (CNTs@PDA). The structure and properties of the CNTs@PDA were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The CNTs and the CNTs@PDA were used as nanofillers and melt-blended into trans-1,4 polyisoprene (TPI) to create shape-memory polymer composites. The thermal stability, mechanical properties, and shape-memory properties of the TPI/CNTs and TPI/CNTs@PDA composites were systematically studied. The results demonstrate that these modifications enhanced the interfacial interaction, thermal stability, and mechanical properties of TPI/CNTs@PDA composites while maintaining shape-memory performance.

Polymer-based actuators: back to the future

Polymer-based actuators play a key role in the area of smart materials and devices, and for this reason different polymer-based actuators have appeared in recent years and are implemented in a broad range of fields, including biomedical, optical or electronics, among others. Although it is possible to find more types, they are mainly classified into two main groups according to their different working principles: electromechanical - with electrical to mechanical energy conversion - and magnetomechanical - with magnetic to mechanical energy conversion. The present work provides a comprehensive and critical review of the recent studies in this field. The operating principles, some representative designs, performance analyses and practical applications will be presented. The future development perspectives of this interesting field will be also discussed. Thus, the present work provides a comprehensive understanding of the effects reported in the past, introduces solutions to the present limitations and, back to the future, serves as a useful guidance for the design of new polymer-based actuators aiming to improve their output performances.

Significant advancements of 4D printing in the field of orthopaedics

Researchers, engineers and doctors are continuously focusing on the development of orthopaedics parts characterised by the required responses. So, advanced manufacturing technologies are introduced to fulfil various previously faced challenges. 4D printing provides rapid development with its capability of customization of smart orthopaedics implants and appropriate surgical procedure. This technology opens up the making of innovative, adaptable internal splints, stents, replacement of tissues and organs. Thus, to write this review based article, relevant papers on 4D printing in medical/orthopaedics and smart materials are identified and studied. 4D printed parts show the capability of shape-changing and self-assembly to perform the required functions, which otherwise manufactured parts are not providing. Smart orthopaedics implants are used for spinal deformities, fracture fixation, joint, knee replacement and other related orthopaedics applications. This paper briefs about the 4D printing technology with its major benefits for orthopaedics applications. Today various smart materials are available, which could be used as raw material in 4D printing, and we have discussed capabilities of some of them. Due to the ability of shape-changing, smart implants can change their shape after being implanted in the patient body. Finally, twelve significant advancements of 4D printing in the field of orthopaedics are identified and briefly provided. Thus, 4D printing help to provide a significant effect on personalised treatments.

Chemical Sand Consolidation: From Polymers to Nanoparticles

The chemical sand consolidation methods involve pumping of chemical materials, like furan resin and silicate non-polymer materials into unconsolidated sandstone formations, in order to minimize sand production with the fluids produced from the hydrocarbon reservoirs. The injected chemical material, predominantly polymer, bonds sand grains together, lead to higher compressive strength of the rock. Hence, less amounts of sand particles are entrained in the produced fluids. However, the effect of this bonding may impose a negative impact on the formation productivity due to the reduction in rock permeability. Therefore, it is always essential to select a chemical material that can provide the highest possible compressive strength with minimum permeability reduction. This review article discusses the chemical materials used for sand consolidation and presents an in-depth evaluation between these materials to serve as a screening tool that can assist in the selection of chemical sand consolidation material, which in turn, helps optimize the sand control performance. The review paper also highlights the progressive improvement in chemical sand consolidation methods, from using different types of polymers to nanoparticles utilization, as well as track the impact of the improvement in sand consolidation efficiency and production performance. Based on this review, the nanoparticle-related martials are highly recommended to be applied as sand consolidation agents, due to their ability to generate acceptable rock strength with insignificant reduction in rock permeability.

3D printed biodegradable functional temperature-stimuli shape memory polymer for customized scaffoldings

Shape memory polymers (SMPs) and their composites have become the prominent choice of the various industries owing to the unique inherent characteristics which can be stimulated through the exposure of external stimuli. The use of SMPs in the three-dimensional (3D) technologies has produced enormous advantages. However, the potential of SMPs in 3D printing has limitedly explored. In the present study, an investigation was performed to study the shape memory effect (SME) of the fused filament fabricated (FFF) chitosan (CS) reinforced poly-lactic-acid (PLA) based porous scaffolds. Firstly, the composite filaments, with 1, 1.5, and 2% wt. of CS, were fabricated by using the twin-screw extrusion process, which was later used to print the test specimens at different infill density. The printed samples were selectively pre-elongated to 2.5 mm and then processed through direct heating, at 60-70 °C, for enabling the SME. It has been observed that the CS particles acted as rigid phases and interrupted the re-ordering of PLA chain. However, the scaffoldings showed 18.8% shape recovery at optimized process parametric settings. In addition, wettability and biocompatibility analyses of developed scaffoldings have also been performed to investigate the biological aspects of the developed scaffoldings. The stimulated samples found to be possessed with good wettability and cell proliferation. Overall, the 3D printed PLA/CS porous scaffoldings have shown significant shape recovery characteristics and are biologically active to be used as self-healing implants for acute bone deficiencies.

Review of Polymeric Materials in 4D Printing Biomedical Applications

The purpose of 4D printing is to embed a product design into a deformable smart material using a traditional 3D printer. The 3D printed object can be assembled or transformed into intended designs by applying certain conditions or forms of stimulation such as temperature, pressure, humidity, pH, wind, or light. Simply put, 4D printing is a continuum of 3D printing technology that is now able to print objects which change over time. In previous studies, many smart materials were shown to have 4D printing characteristics. In this paper, we specifically review the current application, respective activation methods, characteristics, and future prospects of various polymeric materials in 4D printing, which are expected to contribute to the development of 4D printing polymeric materials and technology.

Prospective Design, Rapid Prototyping, and Testing of Smart Dressings, Drug Delivery Patches, and Replacement Body Parts Using Microscopy Aided Design and ManufacturE (MADAME)

Natural materials exhibit smart properties including gradients in biophysical properties that engender higher order functions, as well as stimuli-responsive properties which integrate sensor and/or actuator capacities. Elucidation of mechanisms underpinning such smart material properties (i), and translation of that understanding (ii), represent two of the biggest challenges in emulating natural design paradigms for design and manufacture of disruptive materials, parts, and products. Microscopy Aided Design And ManufacturE (MADAME) stands for a computer-aided additive manufacturing platform that incorporates multidimensional (multi-D) printing and computer-controlled weaving. MADAME enables the creation of composite design motifs emulating e.g., patterns of woven protein fibers as well as gradients in different caliber porosities, mechanical, and molecular properties, found in natural tissues, from the skin on bones (periosteum) to tree bark. Insodoing, MADAME provides a means to manufacture a new genre of smart materials, products and replacement body parts that exhibit advantageous properties both under the influence of as well as harnessing dynamic mechanical loads to activate material properties (mechanoactive properties). This Technical Report introduces the MADAME technology platform and its associated machine-based workflow (pipeline), provides basic technical background of the novel technology and its applications, and discusses advantages and disadvantages of the approach in context of current 3 and 4D printing platforms.

Additive Manufactured Sandwich Composite/ABS Parts for Unmanned Aerial Vehicle Applications

Fused deposition modelling (FDM) is one of most popular 3D printing techniques of thermoplastic polymers. Nonetheless, the poor mechanical strength of FDM parts restricts the use of this technology in functional parts of many applications such as unmanned aerial vehicles (UAVs) where lightweight, high strength, and stiffness are required. In the present paper, the fabrication process of low-density acrylonitrile butadiene styrenecarbon (ABS) with carbon fibre reinforced polymer (CFRP) sandwich layers for UAV structure is proposed to improve the poor mechanical strength and elastic modulus of printed ABS. The composite sandwich structures retains FDM advantages for rapid making of complex geometries, while only requires simple post-processing steps to improve the mechanical properties. Artificial neural network (ANN) was used to investigate the influence of the core density and number of CFRP layers on the mechanical properties. The results showed an improvement of specific strength and elastic modulus with increasing the number of CFRP. The specific strength of the samples improved from 20 to 145 KN·m/kg while the Young's modulus increased from 0.63 to 10.1 GPa when laminating the samples with CFRP layers. On the other hand, the core density had no significant effect on both specific strength and elastic modulus. A case study was undertaken by applying the CFRP/ABS/CFRP sandwich structure using the proposed method to manufacture improved dual-tilting clamps of a quadcopter UAV.