ME353_GROUP 7.pptx mechanical enginnerring

additive manufacturing

1. ME-353 Electronic Devices and their Applications AUXETIC LATTICE STRUCTURE FOR BIO IMPLANTS HEMANT KUMAR [B21294] ABHISHEK [B21270] PRESENTED BY

2. AUXETIC MATERIAL Auxetic structures : →The word ‘auxetic’ derives from the Greek word ‘ auxetikòs ’, whose meaning is ‘tending to increase’. →Generally, materials are contracted in the direction orthogonal to load by reducing their section. → Materials characterised from auxetic structures show an opposite behaviour by revealing a complex flexure, which results as a whole in an increased section in the direction orthogonal to load (Evans and Alderson, 2000). →Auxetic behaviour is not related or specific to any particular material, being purely a consequence of how the material itself is structured microscopically. → In engineering terms, Poisson’s ratio is the ratio between the transverse and the longitudinal strain ( εy / εx ) produced by the application of a load F orthogonal to its section. →Auxetic materials show a negative Poisson’s ratio (NPR), ranging from 0 to –1, while common materials, also defined as ‘Newtonian’, have a positive Poisson’s ratio.

3. LATTICE STRUCTURE Lattice structures are a type of porous design which are used in various fields →Auxetic lattice structures are a type of lattice structure that exhibits a negative Poisson's ratio. →This means that when they are stretched, they get thicker in the direction of the applied force. → This is in contrast to most materials, which get thinner when they are stretched.

4. The negative Poisson's ratio of auxetic lattice structures is caused by their unique geometry. The unit cell of an auxetic lattice structure is typically shaped like a re-entrant honeycomb, which means that the edges of the unit cell are bent inwards. When the unit cell is stretched, the edges rotate outwards, causing the structure to get thicker.

5. Overview Advantages of Bioimplants Bioimplants are medical devices that are used to replace or support a damaged biological structure in the body. They play a vital role in enhancing the quality of life for patients who have suffered from injuries or ailments. In recent years, there has been a growing interest in the use of lattice structures as an alternative to traditional normal structures in bioimplants. Lattice structures offer unique advantages that make them a promising option for various applications. Enhanced Quality of Life: Bioimplants restore and improve bodily functions, allowing individuals to regain their independence and enjoy a higher quality of life. Biocompatibility: These devices are made from materials that are compatible with the body, reducing the risk of rejection or adverse reactions. Long-term Durability: Bioimplants are designed to withstand the test of time, providing long-lasting benefits for patients. WHAT ARE BIO IMPLANTS

6. WHY AUXETIC LATTICE STRUCTURE ARE PREFERRED IN BIO-IMPLANTS ? Auxetic lattice structures are more preferred in bio-implants than the normal lattice structures for several reasons. First, auxetic lattice structures have a negative Poisson's ratio, which means that they expand when stretched and contract when compressed. This property makes them ideal for bio-implants, as it mimics the mechanical properties of natural bone. Natural bone is a porous material with a negative Poisson's ratio, which allows it to absorb and dissipate stress. Auxetic lattice structures can also be designed to have a porosity that is similar to that of natural bone, which can further promote bone ingrowth and osseointegration

7. Auxetic lattice structures are very tough and can withstand a lot of deformation before they break. This makes them ideal for bio-implants, as they can withstand the stresses that are placed on them during movement. Conventional lattice structures, on the other hand, are more brittle and can break more easily. Auxetic lattice structures can be designed to have a specific surface topography that can promote cell adhesion and growth. This is important for bio-implants, as it allows cells to attach to the implant and form new bone. Conventional lattice structures, on the other hand, typically have a smooth surface that is not as conducive to cell adhesion and growth. Finally, auxetic lattice structures can be made from a variety of materials, including biocompatible metals, polymers, and ceramics. This makes them versatile and allows them to be tailored to specific applications. Conventional lattice structures, on the other hand, are typically made from a limited number of materials, which can limit their use in bio-implants. Overall, auxetic lattice structures have a number of advantages over conventional lattice structures that make them ideal for bio-implants. Their negative Poisson's ratio, toughness, surface topography, and versatility make them a promising material for a variety of bio-implant applications. WHY AUXETIC LATTICE STRUCTURE ARE PREFERRED IN BIO-IMPLANTS ?

8. FABRICATION OF AUXETIC BIO MATERIALS →The advancements in fabrication methods have enabled researchers and manufacturers to produce complex structures with advanced materials. →Techniques such as laser cutting and lithography are effective in creating 2D structures, but for 3D auxetic materials, the most widely used method is additive manufacturing or 3D printing. →This method allows for the fabrication of 3D structures at various scales using materials ranging from polymers to metals. → The process involves creating a computer-aided design (CAD) of the desired structure, selecting the materials, and then printing the geometry layer by layer. →Additive manufacturing provides the flexibility to produce both low-cost prototypes and sophisticated finished products, making it increasingly popular in the manufacturing industry.

9. Back to Agenda 08 Different techniques that are used for manufacturing of auxetic bio materials: 1. Stereolithography (SLA) is a form of additive manufacturing (AM) that uses a laser to create three-dimensional objects from a liquid photopolymer resin. The process works by hardening the resin layer by layer, using a UV laser to trace the desired shape of the object.

10. working process Advantages The SLA process begins with a 3D model of the desired object. This model is then sliced into thin layers, typically 0.05-0.15mm thick. The laser then traces the shape of each layer onto the surface of the resin, hardening it in place. The platform then lowers, and the laser cures the next layer of resin. This process continues until the entire object has been built High precision and accuracy, Fast and efficient, variety of photopolymer resins available for SLA printing, with different properties and applications. HOW STEREOLITHOGRHY WORKS

11. 2.DIGITAL LIGHT PROCESSING The DLP method improves upon SLA by offering sub-micron resolution and the ability to print various materials, including polymers, resins, and even some metals. With DLP, the liquid polymer is exposed to selected light from a projector through a system of lenses. This method is even faster than SLA and supports continuous printing of multilayer structures due to the efficient curing or photopolymerization step. The advancements in DLP technology have contributed to the rapid development of 3D auxetic materials, providing enhanced resolution and material flexibility. Working Principle: 3D Model Preparation: A 3D model of the desired object is generated. Slicing: The 3D model is sliced into thin layers. Photopolymer Resin Preparation: A photopolymer resin is placed under the DMD projector. Light Projection and Curing: The DMD projects light patterns onto the resin, curing it layer by layer. Layer-by-Layer Build: The build platform is lowered after each layer is cured, allowing the next layer to be projected and curedxt

12. 3.FUSED DEPOSITION MODELING (FDM) Fused Deposition Modeling (FDM) is another widely used additive manufacturing technique for fabricating auxetic materials. FDM involves melting a thermoplastic filament and depositing it in layers to create the desired structure. The flexibility and affordability of FDM printers make them accessible for both prototyping and commercial production. By carefully controlling the deposition process and optimizing the filament material, FDM can produce auxetic materials with tailored properties, making it a valuable method in the fabrication process. Advantages of FDM: Easy to use Affordable Versatile High precision Wide range of applications

13. CASE STUDIES AND APPLICATIONS: Studies by the research group of Mehmood et al. involved the manufacture of a polyurethane-based auxetic polymeric bone plate, which can be used as an internal fixator for fractures of long bones. The manufactured construction, in contrast to conventional implants the auxetic implants for the hip stem , allows micromovement, which is of great importance in the process of bone healing. In this case, according to references, micromovement is desirable for the formation of callus , facilitating the connection of Bone fragments . The fabrication of the bone auxetic plate was performed using the injection moulding technique discussed by Ali et al. The authors showed that the auxetic bone plate has a potential use for fixing the bone in cases where protection against stress shielding and the creation of micromotions is required. Arguably, manufacturing these solutions employing resorbable materials may benefit from auxetic behaviour during healing and lead to a natural state after resorption. 1.Fixation for Long Bones:

14. 2.SPINAL SURGERY: Artificial intervertebral discs made of high-density auxetic polyethylene can bend and twist and may provide improved biomechanical performance compared with traditional disc replacement solutions. Thanks to its negative Poisson’s ratio, the disc prevents bulges that could injure the surrounding nerve endings. Importantly, the disc perfectly mimics the behaviour of a natural lumbar intervertebral disc. Later, Baker put forward a theory on the use of auxetic foams as a material for an artificial intervertebral disc. Auxetic foam has a re-entrant cellular structure with a negative Poisson’s coefficient after heating by triaxial compression. Finite element analysis showed that the use of an artificial intervertebral disc with a negative Poisson’s ratio would be a solution to the problem, as damage to the surrounding nerves by the intervertebral disc is eliminated . As another application linked to spinal surgery, Yan Yao et al. proposed an auxetic pedicle screw based on a Ti6Al4V resin cell (DPR New Materials Technology Co., Ltd., Beijing, China) to improve the biomechanical interaction between the surrounding bone and the screw, mainly for the spine. According to the results of the finite element method (FEM), the correspondence between Young’s modulus of bone and screw is a necessary condition of pull-out protection for a particular bone .

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