Applications In Medical Implants Research Articles

Tuneable mechanical performance and reusability of 4D-printed heterogeneous metamaterials using shape memory biomass-derived polymer

ABSTRACT Herein, hybrid triply periodic minimal surfaces (TPMS) metamaterials were structurally designed and additively manufactured via 4D printing using a biomass-derived shape memory polymer. Two TPMS topologies including gyroid and diamond with homogeneous and graded structures were separately generated by adjusting the C parameter. The mechanical performance and deformation behaviour between the uniform and graded structures were compared, and the compressive shaping-recovery cycles were conducted. The results showed that the gyroid (C:0.7→0.4) and diamond (C:0.7→0.4) samples exhibited superior reusability to the uniform counterparts. Subsequently, heterogeneous metamaterials assembled by gyroid and diamond subsections were established and 4D-printed. It was observed that both the yielding and shape recovery were preferred occurring in the gyroid part, while the diamond subsection played a stronger supporting effect. Therefore, the compressive performance and deformation mode could be feasibly tuned by the hybridisation of TPMS, which broadened the functional and sustainable applications in energy absorption, intelligent protection and medical implants.

A Comparative Review on Acoustic and Inductive Power Transfer

Wireless Power Transmission (WPT) has emerged as a prominent player in numerous industries recently. It is already established in wireless charging for electric cars and electronic gadgets. However, it has promising applications in medical implants and imaging as well. Among several proposals, Inductive Power Transfer (IPT) and Acoustic Power Transfer (APT) have shown a major impact on this area of interest. This paper presents a comparison between IPT and APT for wireless power transmission (WPT). Most recent proposals are reported, and several key parameters are considered to evaluate the proposals. That includes operating frequencies, separations gaps, powers and power transmission efficiencies and experimental validity. It is found from the review that; a maximum 818 kW of power is transmitted using IPT for electric vehicles. However, APT can transmit 1.068 kW and 5.4 W through wall and in-body medium (implants). Over 90% efficiencies are found for both APT and IPT. In fact, power transfer with 95.66% efficiency over a 6 cm distance of 23.4 W is achieved for APT and 95.6% with 20 cm separation gaps is achieved for IPT for 20 kW power. A wide range of frequencies are applied for both APT and IPT. However, lower frequencies are mostly suitable for high power, more specifically less than MHz ranges. Naturally, lower frequencies are preferable for low power high efficiencies.

Spectroscopic evaluation of nitrogen glow discharge for the surface nitriding of Ti-6Al-4V alloy

The study investigates the spectral characteristics of a DC glow discharge generated in a parallel electrode configuration for nitriding the Ti-6Al-4V alloy to enhance its surface properties. At first, optical emission spectroscopy (OES) was used to optimize the glow discharge for a certain nitrogen fill pressure and discharge power. The Ti-6Al-4V alloy is then subjected to plasma treatment in an optimized N2-discharge environment. The treated samples' microstructures, surface morphology, elemental composition, and surface roughness are all determined by several material characterization techniques, including XRD, SEM, EDX, and AFM. The Ti-alloy's crystalline phase distribution affects the alloy's physical and chemical characteristics, which determine its suitability for various applications in aerospace and medical implants. A phase shift from Ti(101)α to Ti(110)β is observed owing to the progressive increase in nitrogen interstitials in Ti sites, which promotes the phase transition. The EDX results show that the amount of nitrogen in the spectrum increases, demonstrating that nitrogen has successfully been incorporated into the surfaces of alloys. The surface morphology of the treated samples has improved with longer treatment times, as seen by SEM pictures of samples that have received plasma treatment. Finally, the comparison of the samples' AFM topological measurements and textures at 5, 10, and 15 h demonstrates the importance of treatment time on the development of the Ti-6Al-4V surface roughness and microstructure.

Wirelessly powered motor operation in dynamic scenarios using non-Hermitian parity-time symmetry

Motors arise as a heart of the mobility society, and wirelessly operated motors may improve our standard of living. Wireless power transfer in the kilohertz and megahertz range has been extensively explored, finding various potential applications in consumer electronics, electric vehicles, and medical implants. However, stable operation of wirelessly powered motors remains challenging due to voltage fluctuations for motors occurring in dynamic scenarios, e.g., the rotating speed of the motors is varied. Here, we theoretically and experimentally demonstrate the operation of a motor, where the power is wirelessly transferred via coils, is robust against the rotating speed by employing the analogy with non-Hermitian parity-time (PT) symmetry. In addition, our system is robust for misalignment of the coils. Our results open up opportunities for the robust operation of motors via wireless power transfer in dynamic scenarios towards autonomous vehicles.

Investigating the Degradation Behavior of Grain Refined WE43 Magnesium Alloy Produced by Friction Stir Processing for Medical Implant Applications

Developing Magnesium (Mg) based degradable implants for orthopedic applications is an attractive research area for the past two decades in the biomedical engineering. Mg is well accepted by human system and does not cause any health abnormalities during its degradation in the physiological environment. However, in order to improve its life span by controlling the aggressive degradation, novel Mg alloys are developed and subjected to different treatments to enhance their performance to tailor as promising candidates for implant manufacturing. In this context, recently, a special attention is paid towards using rare earth containing Mg alloys due to their excellent mechanical and corrosion resistance properties. Hence, in the present work, WE43 Mg alloy has been selected and the microstructual modification was carried out by friction stir processing. The role of grain refinement on the degradation behavior of FSPed WE43 Mg alloy was assessed by immersing the samples in simulated body fluids. From the microstructural studies, grain size reduction from 46 ± 4.2 µm to 16.1 ± 5.4 µm was achieved after FSP. The larger intermetallic particles were also observed as dissolved into the solid solution grains and fewer intermetallic particles were remained in the stir zone of FSPed alloy. After immersion studies, the surface of the samples was deposited with mineral phases and were analyzed by X-ray diffraction analysis and scanning electron microscope and found that the grain refinement achieved by FSP has a significant effect on increasing the mineral depositions which helps to control the degradation rate of the samples.

Rational design and additive manufacturing of grain boundary-inspired, multi-architecture lattice structures

The advent of additive manufacturing has facilitated the design and fabrication of hybrid lattice structures with multiple morphologies. These structures combine multiple distinct architectures into a single structure with an exceptional performance that far exceeds that of each constituting architecture. However, combining strut-based lattices poses serious challenges in establishing effective connections, primarily due to complications in formulating mathematical expressions. Here, we introduce a novel approach, inspired by the connections observed in the grain boundaries of polycrystalline materials, to design the interconnections of hybrid structures. This strategy involves shrinking the unit cell linkage, thereby addressing the difficulty of forming efficient connections at arbitrary spatial interfaces within strut-based lattice structures. We then use the relevant design theories to tune the performance of these connections and simplify the design process for hybrid structures – even for inexperienced designers. Our experimental observations confirm the efficacy of the proposed strategy, bridging the knowledge gap in the design of connected strut-based multi-lattice structures. Furthermore, this approach enhances the design of tailored hybrid structures and fosters the development of metamaterials with advanced, unique functionalities. The proposed approach has important implications for the development of designer materials, with applications in medical devices, (soft) robotics, and implants.

Research Progress of Selective Laser Melting Forming Medical Implants

Abstract:: Selective laser melting technology has the advantages of rapid manufacture, high precision, and the ability to produce fine structures. Medical implants made using selective laser melting technology have high precision and excellent mechanical properties that meet the needs of patients and make medical implants more promising in the medical field. This paper reviews the progress of research on selective laser melting of medical implants. This paper draws on numerous journals and patents. This paper firstly reviews the classification of medical implants, mainly including hip implants, knee implants, maxillo-craniofacial implants and spinal implants. Secondly, the common porous structure design methods, the effect of porous structure on the mechanical properties of the implant, and the effect of pore structure on the growth properties of porous titanium alloy bone are summarised. Finally, the process of manufacturing titanium alloy implants by selective laser melting technology is described. Medical implants made by selective laser melting have excellent properties and are widely used in the medical field. Compared to traditional mechanical processing methods, selective laser melting technology can better preserve the properties of the raw material, while providing higher precision and faster preparation. However, selective laser melting has a number of drawbacks, including differences in material microstructure, reduced strength and plasticity, inadequate surface treatment, and enhanced safety and reliability. Further scientific research and technological innovation are needed to solve these problems. In the future, as technology continues to innovate and develop, SLM technology will become more mature, resulting in implants that are more natural, suitable for the body and long-lasting. At the same time, as implants are personalised, there will be a huge market demand and development opportunities. In addition, the continuous improvement of regulatory policies is expected to further promote the market development and application of medical implants.

Impact of tetra ethyl ortho-silicate and magnesium nitrate hexahydrate on dielectric characteristics of forsterite powder

Forsterite powder with different compositions of tetra ethyl ortho-silicate (TEOS) and magnesium nitrate hexahydrate (MNH) is synthesized using the sol-gel method. X-ray Diffraction (XRD) technique is used for structural analysis and phase identification for forsterite powder. Surface morphology and elemental composition of forsterite samples are also investigated using scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) techniques. In addition, an extensive study is performed to estimate the dielectric properties (dielectric constant, dielectric loss, alternating current conductivity and loss tangent) and their relationship with frequency at room temperature in the frequency range of 200 MHz–20 GHz using a vector network analyzer (VNA) assembly. Furthermore, the intense effect of TEOS and MNH on surface morphology and dielectric properties of forsterite powder is also discussed in detail by focusing on the application in medical implants.

Miniature Integrated 2.4 GHz Rectennas Using Novel Tunnel Diodes.

This work presents the design, fabrication, and measured results of a fully integrated miniature rectenna using a novel tunnel diode known as the Asymmetrical Spacer Layer Tunnel (ASPAT). The term rectenna is an abbreviation for a rectifying antenna, a device with a rectifier and antenna coexisting as a single design. The ASPAT is the centrepiece of the rectifier used for its strong temperature independence, zero bias, and high dynamic range. The antenna is designed to be impedance matched with the rectifier, eliminating the need for a matching network and saving valuable real estate on the gallium arsenide (GaAs) substrate. The antenna is fully integrated with the rectifier on a single chip, thus enabling antenna miniaturisation due to the high dielectric constant of GaAs and spiral design. This miniaturisation enables the design to be fabricated economically on a GaAs substrate whilst being comparable in size to a 15-gauge needle, thus unlocking applications in medical implants. The design presented here has a total die size of 4 × 1.2 mm2, with a maximum measured output voltage of 0.97 V and a 20 dBm single-tone 2.35 GHz signal transmitted 5 cm away from the rectenna.

Environment-Responsive Therapeutic Platforms for the Treatment of Implant Infection.

The application of medical implants has greatly improved the survival rate and life quality of patients. Nevertheless, in recent years, there have been increasing cases of implant dysfunction or failure because of bacterial infections. Despite significant improvements in biomedicine, there are still serious challenges in the treatment of implant-related infections. With the formation of bacterial biofilms and the development of bacterial resistance, these limitations lead to low efficacy and considerable side effects of conventional antibiotics. To address these challenges, it is urgent to exploit innovative prevention and treatment strategies for implant-related infections. Based on these ideas, environment-responsive therapeutic platforms with high selectivity, low drug resistance, and minor dose-limiting toxicity have attracted widespread attention. By using different exogenous or endogenous stimulations, the antibacterial activity of environment-responsive therapeutic platforms can be activated on demand and exhibit remarkable therapeutic effects. Exogenous stimulations include applications of photo, magnetism, microwave, and ultrasound. Endogenous environmental stimulations are mainly based on the pathological characteristics of bacterial infections, such as acidic pH, anomalous temperature, and abnormal enzymatic activities. In this review, the recent progress of environment-responsive therapeutic platforms with spatiotemporally controlled drug release/activation is systematically summarized. Afterward, the limitations and opportunities of these emerging platforms in the treatment of implant-related infections are highlighted. Finally, we hope that this review will stimulate innovative ideas and offer novel technical methods for the development of environmentally responsive therapeutic platforms for implant-related infection management. This article is protected by copyright. All rights reserved.

Modifying Poly(caprolactone) Degradation through C–H Functionalization

There is a growing need for degradable polymers for applications in sustainable plastics and medical implants. To enhance the utility of degradable polymers, both better understanding of the factors that influence their degradation and new tools to modulate degradation are needed. We report the C–H xanthylation of poly(caprolactone), a biodegradable polyester, which results in changes in materials properties even at small incorporations. Despite the functionalized materials exhibiting a decrease in crystallinity and hydrophobicity, xanthylated poly(caprolactone) degrades more slowly than its unfunctionalized counterpart. To understand this rate difference, kinetic studies with a small-molecule surrogate were performed and demonstrated that functionalization adjacent to the hydrolyzable ester functional group led to slower degradation. This study illustrates how the interplay between molecular and materials characteristics can impact degradation.

A Novel Bio-Adhesive Mesh System for Medical Implant Applications: In Vivo Assessment in a Rabbit Model.

Injectable surgical sealants and adhesives, such as biologically derived fibrin gels and synthetic hydrogels, are widely used in medical products. While such products adequately adhere to blood proteins and tissue amines, they have poor adhesion with polymer biomaterials used in medical implants. To address these shortcomings, we developed a novel bio-adhesive mesh system utilizing the combined application of two patented technologies: a bifunctional poloxamine hydrogel adhesive and a surface modification technique that provides a poly-glycidyl methacrylate (PGMA) layer grafted with human serum albumin (HSA) to form a highly adhesive protein surface on polymer biomaterials. Our initial in vitro tests confirmed significantly improved adhesive strength for PGMA/HSA grafted polypropylene mesh fixed with the hydrogel adhesive compared to unmodified mesh. Toward the development of our bio-adhesive mesh system for abdominal hernia repair, we evaluated its surgical utility and in vivo performance in a rabbit model with retromuscular repair mimicking the totally extra-peritoneal surgical technique used in humans. We assessed mesh slippage/contraction using gross assessment and imaging, mesh fixation using tensile mechanical testing, and biocompatibility using histology. Compared to polypropylene mesh fixed with fibrin sealant, our bio-adhesive mesh system exhibited superior fixation without the gross bunching or distortion that was observed in the majority (80%) of the fibrin-fixed polypropylene mesh. This was evidenced by tissue integration within the bio-adhesive mesh pores after 42 days of implantation and adhesive strength sufficient to withstand the physiological forces expected in hernia repair applications. These results support the combined use of PGMA/HSA grafted polypropylene and bifunctional poloxamine hydrogel adhesive for medical implant applications.

Evaluation of Mechanical Properties of Bio-degradable Hybrid Particulate Fibre Reinforced Polymer Composite

Recent interest in advancement of biomaterials and their implant applications is well known. In the last five decades, great advances have been made in the field of biomaterials, including ceramics, glasses, polymers, composites, glass-ceramics and metal alloys. A variety of bio implants are currently used in body implantation. In the present study, ISO Polymer and crab shell derived hydroxyapatite (HAp) have been selected to develop composites by hand lay-up method targeted for degradable implant applications. Composite was successfully developed with various fractions of crab shell powder (0%, 5%, 10% and 15%) & e-glass fiber was composed to prepared hybrid polymer composites. HAp powder reinforced hybrid polymer composites, SEM studies and mechanical properties (hardness, tensile strength and impact strength) were determined as per ASTM standards. The higher mechanical properties were obtained at 15% Crabshell powder particulate composite. The introduced Crab Shell (HAp) enhances bio mineralization and promotes rapid healing rate in the bio medical implants applications.

Starch Modified Tough Biocompatible Polyurethane/acrylamide bio Composites: Physicochemical Properties and Biodegradation Studies

Biodegradable bio composites with potential applications in medical implants were prepared with starch content by in situ polymerization technique using polyurethane prepolymers. (PU) and acrylamide (AAM) monomers. The structure and properties of bio composites were evaluated. FT-IR spectroscopy showed bonding between N=C=O functional group terminated polyurethanes confirmed improved compatibility of prepolymers, AAM, starch and bio composites. The DSC data are the glass transition (Tg) of the bio composite and ordinary polyacrylamide (PAAM) network. By incorporating starch and polyurethane in the form of an interpenetrating network into a polyacrylamide network, mechanical and thermal properties of bio composites due to higher crosslink density given by hard segment content. We studied the swelling behavior of both bio composites and individual PAAM networks under different pH conditions to validate their biocompatibility and potential use in biomedicine setting. The hydrolytic stability of biocomposites and PAAM networks was investigated using phosphate buffer. Hydrolytic stability of biocomposites was found to be higher comparison with PAAM network. Morphological analysis of the samples showed uniform distribution and good interfacial adhesion. Improves sample biodegradability it was revealed by the soil runoff test.

Developing a Novel Growth Method for Carbon-Infiltrated Carbon Nanotubes on Ti6Al4V

Carbon-infiltrated carbon nanotubes (CICNT) are cylindrical rolls of pure carbon atoms with a honeycomb molecular structure. They have specific applications in medical implants due to their biofilm resistance properties. CICNT can be grown on a variety of material substrates such as silicon, stainless steel, and pure titanium. Different substrates require different CICNT growth processes. This study developed a growth method for CICNT on Ti6Al4V, a titanium alloy commonly used as a medical implant material due to its strong mechanical properties and excellent biocompatibility. However, due to the presence of vanadium in the alloy, it is difficult to use it as a substrate for CICNT growth. To solve this problem, this study used an indirect growth method, which placed a barrier layer of alumina (Al2O3) between the Ti6Al4V and an iron growth catalyst layer. A control group was also created without an alumina barrier layer. This study additionally investigated the differences between two deposition methods: electron-beam physical vapor deposition (PVD) and atomic layer deposition (ALD). After CICNT growth, the samples showed that the deposition of the barrier layer allowed the growth of CICNT on Ti6Al4V. Using a scanning electron microscope (SEM), the results also showed that at the levels of alumina studied, the deposition method did not make a difference to CICNT coverage of the Ti6Al4V. These results illustrate the fact that Ti6Al4V can be used as a substrate for CICNT if a barrier layer is used.

Additive Manufacturing of Polyetheretherketone (PEEK) and its Application in Medical Implants

PEEK is a polyaromatic semi-crystalline thermoplastic polymer with good mechanical characteristics for biomedical applications. The medical field has been applying its mechanical properties to make bone implants and modeling for surgical planning using 3D printing, more formally called Additive Manufacturing (AM). This paper provides a concise discussion about PEEK and its development for orthopedic applications. Some of the designs used to fix specific issues are shown in this review paper including the mechanical properties development for PEEK to be applicable in the medical field. Challenges and prospects when 3D printing using this material on improving PEEK’s biocompatibility and ease of printing are also discussed.

Promising Role of Polylactic Acid as an Ingenious Biomaterial in Scaffolds, Drug Delivery, Tissue Engineering, and Medical Implants: Research Developments, and Prospective Applications

In the present scenario, the research is now being focused on the naturally occurring polymers that can gradually replace the existing synthetic polymers for the development of bio composites having applications in medical surgeries and human implants. With promising mechanical properties and bio compatibility with human tissues, poly lactic acid (PLA) is now being viewed as a future bio material. In order to examine the applicability of PLA in human implants, the current article sheds light on the synthesis of PLA and its various copolymers used to alter its physical and mechanical properties. In the latter half, various processes used for the fabrication of biomaterials are discussed in detail. Finally, biomaterials that are currently in use in the field of biomedical (Scaffolding, drug delivery, tissue engineering, medical implants, derma, cosmetics, medical surgeries, and human implants) are represented with respective advantages in the sphere of biomaterials.

Hyaluronic acid-based nanofibers: Electrospun synthesis and their medical applications; recent developments and future perspective.

Hyaluronan is a biodegradable, biopolymer that represents a major part of the extracellular matrix and has the potential to be fabricated in a fibrous form conjugated with other polymers via electrospinning. Unique physicochemical features such as viscoelasticity, conductivity, and biological activity mainly affected by molecular weight attracted the attention of biomedical researchers to utilize hyaluronan for designing novel HA-based nano-devices. Particularly HA-based nanofibers get focused on a diverse range of applications in medical like tissue implants for regeneration of damaged tissue or organ repair, wound dressings, and drug delivery carriers to treat various disorders. Currently, electrospinning represents an effective available method for designing highly porous, 3D, HA-based nanofibers with features similar to that of the extra-cellular matrix making them a promising candidate for designing advanced regenerative medicines. This review highlights the structural and physicochemical features of HA, recently cited protocols in literature for HA production via microbial fermentation with particular focus on electrospun fabrication of HA-based nanofibers and parameters affecting its synthesis, current progress in medical applications of these electrospun HA-based nanofibers, their limitations and future perspective about the potential of these HA-based nanofibers in medical field.

Biodegradable Materials for Transient Organic Transistors

AbstractElectronic devices that can physically disappear in a controlled manner without harmful by‐products unveil a wide range of opportunities in medical devices, environmental monitoring, and next‐generation consumer electronics. Their property of transience is indispensable for mitigating the global problem of electronic waste accumulation. Additionally, transient technologies that are biocompatible and can be biologically resorbed are of great potential for applications in temporary medical implants, since it eliminates the need for expensive device recovery surgery. Transistors are the key building blocks of modern electronics, and their fabrication using organic materials is beneficial due to their low cost, unprecedented flexibility and facile processing. This contribution reviews the technological application of biodegradable materials in four major classes of organic transistors, namely organic field‐effect transistors (OFETs), organic synaptic transistors, electrolyte‐gated OFETs, and organic electrochemical transistors. The fundamental biodegradation mechanism is discussed in detail, followed by a perspective of various biodegradable materials utilized as active semiconductors, dielectrics, electrolytes and substrates in the various types of organic transistor devices. This contribution comprehensively discusses the role and application of biodegradable materials in all of the key modern‐day organic transistors, highlighting their unique properties that allow the fabrication of biodegradable, eco‐friendly, and sustainable devices.

Mechanical Properties of 3D-Printed PEEK/HA Composite Filaments.

The incorporation of bioactive ceramic into polyether ether ketone (PEEK) was expected to improve the bioinertia and hydrophobicity of pure PEEK, further facilitating osseointegration and bone ingrowth. However, the addition of bioceramic also changes the anisotropy of mechanical properties and failure mechanism of composite. Therefore, three-dimensional printed (3D-printed) PEEK/hydroxyapatite (HA) composite filaments with differing proportions (HA content: 10–30 wt%) were prepared using physical mixture and melting extrusion processes. The tensile elastic modulus and tensile strength of composite filaments were tested experimentally. These microscopic models, with multiple diameter variations and differing dispersity of HA particles, were built to estimate mechanical properties using finite element analysis. Based on a generalized version of Hooke’s Law, the influence of diameter variation and particle clustering on the elastic modulus was evaluated. The mathematical relationship between the elastic modulus and volume fraction of the bioceramic was established using the Halpin–Tsai model. The results showed that with an increase in HA content from 10 wt% to 30 wt%, the elastic modulus of the composite increased from 2.36 GPa to 2.79 GPa, tensile strength decreased from 95 MPa to 74 MPa, and fracture elongation decreased from 63% to 23%, presenting brittle fracture failure. When the dispersion of particles was uniform, the elastic modulus was less affected by diameter variation, but the modulus anisotropic coefficient was greatly affected by the composition ratio, particle diameter, and dispersity. Hence, 3D-printed PEEK/HA composite filaments can meet the strength requirements of human bone, and understanding the influence of mechanical anisotropy plays a very important role in the design, manufacture, and clinical application of medical implants.