Rapid Prototyping.pptx......................

Rapid prototyping

1. Rapid Prototyping

2. Rapid Prototyping Method Imaging of the tissue defect via scanning techniques like, CT, X-ray or MRI to obtain basic information about the defect. CAD solid model- Complex shapes of the scaffold which would fill the defect (as per noted in the scan) are designed using CAD software ‘.STL’ file is generated Slicing the file into layers Final build file Fabrication of part- Scaffolds are fabricated using specific technique Post processing STEPS in general-

3. Rapid Prototyping Method

4. Schematic Representation of Rapid Prototyping Method

5. Rapid Prototyping Techniques Micro fabrication: 1. Solid freeform (SFF) Stereo lithography Analyzer (SLA) Stereo lithography Sintering or Selective laser Sintering (SLS) - Fused Deposition Modeling (FDM) - Three Dimensional Printing (3DP) - Micro syringe Deposition (MD) 2. Lithography Photolithography and etching High aspect ratio Photolithography Micro molding Electroplating 3. Cell Printing Technology

6. Solid freeform (SFF) Process:- CAD is applied to generate a 3D replica of scaffold. This image is organized into 2D slices typically of 100 microns thickness. Scaffolds are produced by mechanically controlling the laser within the horizontal plane forming pattern by polymerizing the monomers in specified locations according to CAD. Important points:- Lateral and vertical resolution depends upon various factors like- The lateral resolution is typically in the range of 50-250µm. Laser spot size is the principal driver of the lateral resolution. Smaller is the laser spot, better is the spatial resolution and thus manufacturing time is increased. Vertical resolution is determined by heat affected zone depth in photo-polymerization process.

7. Principle of SLA SLA was developed in 1986 by 3D Systems The process is based on the following principles: A laser is used to design precise regions of scaffolds through photo-polymerization Parts are built from a photo-curable liquid polymer that solidifies when sufficiently exposed to a laser beam which scans across the surface of the resin The structure is made layer by layer, each layer being scanned by the optical scanning system and controlled by an elevation mechanism which lowers at the completion of each layer This is a direct write method that requires substantial processing time to produce a scaffold of sufficient scale & resolution for complex tissue engineering applications.

8. Process of SLA A liquid state photosensitive polymer solidifies when exposed to a lighting source A platform that can be elevated is located just one layer of thickness below the surface According to the cross section of the part (starting with bottom layer). The laser scans the polymer layer above the platform to solidify the polymer The Platform is lowered into the polymer bath to the layer thickness Steps 3 and 4 are repeated until the top layer of the part is generated Post-curing and part finishing can then be performed

9. Schematic of SLA for polymer solution

10. Applications of SLA Models for conceptualisation, packaging and presentation Prototypes for design, analysis, verification and functional testing Masters for prototype tooling and low volume production tooling Patterns for investment casting, sand casting and moulding Tools for fixture and tooling design and production tooling Advantages of SLA High accuracy Surface quality is good Used for fabricating parts of varied sizes- from small pin to car dash board

11. Selective Laser Sintering (SLS) Process :- Roller spreads powder over a platform. According to structural information obtained from CAD, the scanner performs polymerization and sintering of powder (thus first layer from the bottom is formed). This is done by CO 2 laser that provides concentrated heating beam which is traced over tightly compacted layer of fine heat fusible powder. Platform moves one step down and above steps are repeated till the desired scaffold structure is obtained.

12. Advantages of SLS: Rapid manufacturing Large and complex functional parts can be manufactured in less time

13. Fused Deposition Modeling (FDM) Also known as Biological Particle Manufacturing (BPM) x-y-z plotter is utilized which has vertical stepping capability. Process:- According to the scaffold structure designed using CAD, molten scaffold material such as polymer or ceramics are ejected from a nozzle on to a surface Continuous deposition of molten material on a solidified surface leads to formation of a particular 3D scaffold structure. Porosity is generally not as high as it is with other technique.

14. FDM Representation:

15. Parts of a FDM Machine Raw material: The raw material mostly used in this process is generally thermoplastic filaments or thermoplastic beads. ABS (Acrylonitrile Butadiene Styrene) material, polyamide, polycarbonate, polyethylene, polypropylene, and investment casting wax are the raw materials that are used in the technique. Supporting materials are also used along with the main raw material. Extrusion nozzle : This is an important part of the apparatus from which metal gets heated up and liquefied. The extrusion nozzle can be moved along the X-Y plane only. Stepper motors : The stepper motor helps to move the nozzle according to the CAM (Computer-Aided Manufacturing) program code which defines the path of the motion of nozzle. Nozzle tip: This nozzle tip is the last point from which hot thermoplastic will get deposited on the platform. Drive wheels : The drive wheels will provide the required feed for the filaments so that it properly moves into the liquefier. Liquefier : This part of the set up liquefies the thermoplastic filament to molten state, which is then deposited on the platform. Platform : This is the base on which fused deposition model is produced.

16. Advantages of FDM Economical technique for making medium sized parts Parts having greater stability can be manufactured Low end, economical machines. No post curing required Variety of materials can be used Easy material changeover Disadvantages Can not be applied for polymer solution Not good for small features, details and thin walls. Surface finish Supports required on some materials / geometries. Support design / integration / removal is difficult. Weak Z-axis. Slow on large / dense parts.

17. Three Dimensional Printing (3DP) 3D printers use a variety of very different types of additive manufacturing technologies, but they all share one core thing in common: they create a three dimensional object by building it layer by successive layer, until the entire object is complete. Steps- The file — a Computer Aided Design (CAD) file — is created with the use of a 3D modeling program, either from scratch or beginning with a 3D model created by a 3D scanner. Either way, the program creates a file that is sent to the 3D printer. Software slices the design into hundreds, or more likely thousands, of horizontal layers. 3DP utilizes a scanning system that directs a writer towards specific positions on a 2D plane. Then a jet of chemical binder is applied towards the powder bed which binds the powder. The platform then steps down in vertical direction to write next layer. These layers will be printed one atop the other until the 3D object is formed. 

18. Advantages of 3DP Very fast Cost effective Manufacturing of coloured parts is also possible

19. 3D Printers CAD designed structure Three Dimensional Printing (3DP)

20. Lithography Techniques 1. Photolithography and Etching Photolithography is used to pattern substrates for formation of topographic features and spatial features like, formation of micro channels, adhesive or non-adhesive regions. Comprises the application of thin layers of photoresist followed by plasma etching – this produces topographic or spatial features on substrate. For nanoscale features- advanced lithographic processes are applied like- Conformable Contact Lithography (CCL) Deep reactive ion-etching (DRIE)

21. Lithography Techniques 2 . High aspect ratio Photolithography A high energy beam is used to expose thick polymeric film to obtain desired structure on the surface of Si wafers. Layers of thickness ranging from 25 µm to several hundred microns are deposited and patterned to produce thicker layers of complex 3D structure.

22. Advantages Best method to control pore size Best method for preparing complex shaped scaffolds Energy & Time Efficient Disadvantages Applicable to limited polymers Sophisticated method Heterogenous pore morphology is not possible