| Author | Thittikorn Phattanaphibul |
| Call Number | AIT Diss. no.ISE-12-16 |
| Subject(s) | Rapid prototyping
|
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctoral of Engineering in Industrial and Manufacturing Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ISE-12-16 |
| Abstract | Rapid prototyping (RP) is a technology that allows the complex prototypes to be directly and rapidly created from their 3D-CAD models. With its flexibilities and production speed, RP has been well accepted and widely used in several applications including in medical area. It has been recognized as medical rapid prototyping (MRP) which is the fabrication of prototypes of human anatomy used for various purposes such as implantations, surgery planning instruments, learning tools and temporary structure for tissue engineering known as scaffold. In particular to scaffold fabrication, RP has been considered as an ideal technology that can overcome the limitations found in the conventional scaffold fabrication technique. Both commercial and in-house developing RP techniques have been applied for this application. The objective of this research is to increase the capabilities of selective vacuum manufacturing (SVM) to be able to apply in temporary scaffold fabrication. SVM is a new RP technique that combines sand casting and powder sintering processes for constructing a prototype layer by layer. A dense layer of support material is prepared and selectively removed to create a cavity profile where the part material is deposited into and sintered to form a solid layer. Recently, its application has been extended to a medical application, in particular to scaffold fabrication. Preliminary studies illustrated the potential promise of SVM technique for this application but also suggested further developments. Therefore, SVM has been researched in this study to improve the properties of scaffolds to meet the requirements. In order for SVM to be considered in this medical application, the fabricated scaffolds must achieve the requirements that cover structural, mechanical and biological properties and the following actions have been made on the part/support materials and the SVM process parameters. Biocompatible/biodegradable polymers are widely used as material for temporary scaffold. In order to apply them in SVM technique, their commercial pellets must be transformed into loose powder form. Rather than mechanically crushing that is not suitable for polymer material due to its tacky nature, a new powder preparation method has been introduced and implemented on poly-lactic acid (PLA), a scaffold material. An experiment has been conducted to determine the condition to produce loose PLA powder. The produced powder has been investigated for its properties. Results illustrated a concern on its flowability that has led to additional experiments to determine the process condition to improve this property. Besides, this method has also been applied to prepare loose powder from poly- caprolactone (PCL) and PLA/PCL composite.To prevent contamination from silica sand typically used as support material, table salt has been used as a new support material since its residue can be removed very easily with water. Attempts have been put to determine the condition that table salt can maintain its shape as a mold. This property is very vital especially for scaling down feature size of the scaffold. A binding agent is mixed into the table salt to improve this property and the experiments have been conducted to determine the composition the support material and process parameters used for creating good cavity profile. Besides biological requirement, the structural and mechanical requirements of the scaffolds are also important that are typically the results from the process condition of the fabrication technique. The scaffold should have high porosity to encourage the distribution of nutrients and/or cells throughout the structure and have sufficient strength to sustain the load during tissue regeneration. Preliminary studies suggested adjustments of the process condition of iv SVM technique to achieve these scaffold properties. Density of PLA powder packed within the cavity and sintering temperature have been considered that have major impact on both porosity and strength of the fabricated scaffolds. The experiments have been conducted to determine their suitable parameters for this issue. The fabricated scaffolds have been assessed by using SEM analysis, porosity calculation, compression test and indirect-cytotoxicity test. Results illustrated that SVM technique can be considered for soft tissue application. Apart from improving the fabrication technique, a medical SVM (MSVM) machine has been redesigned from the previous SVM machine to be more suitable for scaffo ld fabricat ion. The future attempts will be on making SVM closer to the real usage such as (1) conducting a direct cytotoxicity test, (2) scaling down the scaffold size toward micro-level, and (3) improving SVM technique to achieve the requirements for hard tissue application. |
| Year | 2012 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ISE-12-16 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Industrial Systems Engineering (DISE) |
| Academic Program/FoS | Industrial Systems Engineering (ISE) |
| Chairperson(s) | Pisut Koomsap; |
| Examination Committee(s) | Huynh Trung Luong ;Pitt Supaphol; |
| Scholarship Donor(s) | Royal Thai Government ;Royal Thai Government; |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 2012 |