Int J Adv Manuf Technol (2002) 19:217–223  2002 Springer-Verlag London Limited Investigation of 3D Non-Random Porous Structures by Fused Deposition Modelling M. H. Too 1 , K. F. Leong 1 , C. K. Chua 1 , Z. H. Du 1 , S. F. Yang 1 , C. M. Cheah 1 and S. L. Ho 2 1 School of Mechanical and Production Engineering, Nanyang Technological University, Singapore; and 2 Mechanical Engineering Department, Singapore Polytechnic, Singapore The development of 3D non-random porous structures for biomedical applications has been of interest for many years. Processing of these 3D non-random porous structures using the fused deposition modelling (FDM) process is presented in this paper. The FDM built structures were evaluated to deter- mine their suitability for use in the area of tissue engineering. The influence of process parameters on the porosity, pore diameter and compressive strength of the porous structures was investigated. The FDM process was found to be able to provide good control and reproducibility of the desired degree of porosity and 3D microstructure. This technology also offers flexibility and ease of varying the microstructure to meet specific structural and functional requirements for tissue engin- eering. Keywords: Biomedical application; Fused deposition model- ling (FDM); Porous structure; Rapid prototyping (RP); Raster gap; 3D microstructure 1. Introduction The development of specially designed porous structures (i.e. scaffolds) for biomedical application in the area of tissue engineering, has been a major focus in current biomedical research. Among the most important features required in scaf- folds built for tissue engineering purposes, are porosity, pore diameter, and mechanical strength. The regeneration of specific tissue cells seeded on a scaffold is shown to be dependent on the porosity and the pore size of its structure. A large pore volume is required to accommodate and deliver the cells for tissue repair, whereas a high surface area favours cell attach- ment and growth. For scaffold designs, appropriate pore sizes must be incorporated for the delivery of a large number of cells to accelerate bone-remodelling [1]. There have been sev- Correspondence and offprint requests to: Dr C. K. Chua, School of Mechanical and Production Engineering, Nanyang Technological University, Nanyang Avenue, 639798, 2263, Singapore. E-mail: mckchuantu.edu.sg eral efforts to produce scaffolds with 3D pore inter-connectivity for tissue-engineered implants using different processing tech- niques, such as, fibre bonding, solvent casting, particulate leaching, melt moulding, and membrane lamination [2–5]. Unfortunately, most of these processes generate scaffolds with unpredictable pore sizes and arrangements owing to their lim- ited flexibility in controlling the pore volume and distribution. Moreover, the generated scaffolds lack structural stability and have poor mechanical strength. With the introduction of rapid prototyping (RP) technology [6], scaffolds suitable for tissue engineering can be produced with 3D microstructures contain- ing consistent pore sizes and arrangements [7–12]. In addition, RP technology offers the ease and flexibility to meet scaffold characteristics in terms of the structural and functional require- ments specified for use in different applications of tissue engin- eering. Fused deposition modelling (FDM), developed by Stratasys [13], is among one of the most popular RP processes. It creates physical objects directly from CAD 3D solid models via computer-controlled robotic extrusion of a small polymeric road in an additive layer-by-layer material deposition process [14,15]. This polymeric material is vertically stacked layer-by- layer and consists of material “roads” or “raster lines” with pre-defined voids called raster gaps. The ability of the FDM process to pre-define the raster gap enables it to create a non- random porous 3D object with a predictable and intended microstructure for a specific parameter setting. This paper studies the feasibility of employing the FDM technique in scaffold building. Fundamental studies were car- ried out on the microstructure of FDM parts to determine their conformity to scaffold requirements. Initial studies were conducted to investigate the influence of the raster gap process parameter for the porosity, pore diameter, and strength of the FDM parts. These studies will determine the suitability of the FDM process for providing an effective and high degree of control over the sizes of the pores generated, and the uniformity of their arrangement within the part. A mathematical model to predict the porosity of FDM built structures with prespecified process parameter settings is presented.