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Received Oct 24, 2017; Revised Feb 13, 2018; Accepted Mar 27, 2018
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
Biodegradable materials are drawing increasing attention in the field of 3D printing because they can be used to print body implants, tissue engineering scaffolds, and even drug-releasing capsule [1–3]. So far, polylactic acid (PLA) is one of the most common biodegradable materials used in 3D printing [4–6]. PLA can be easily heated above its melting temperature of 150°C–160°C and squeezed out from a nozzle in a 3D printer based on fused deposition modeling (FDM) [7, 8]. The major problem of FDM 3D printers is that they have low resolution compared with using stereolithography (SLA) or digital light processing (DLP) 3D printers [9, 10]. Another problem of FDM 3D printers is the slow printing speed because it forms a 3D object by stacking many thin material lines, consequently taking several hours to print a small object [11, 12]. This study developed biodegradable materials for use in DLP 3D printers in the near future.
The biodegradability of common polymers, such as polyglycolide (PGA), PLA, and polycaprolactone (PCL) polyesters, depends on their structures [13–15]. Their ester bonds undergo hydrolysis on reaction with water. Polyesters with longer alkyl backbone and more alkyl side chains are less hydrophilic and therefore have a longer degradation rate [16]. In general, PCL has a longer degradation rate than does PLA, and PLA shows a longer degradation rate than does PGA. Because of its longer degradation time, PCL has several potential tissue engineering and medical 3D printing applications.
PCL is a popular biodegradable material for resin additives, small scale modeling, and bone tissue engineering [17–22]. It can be synthesized by the ring-opening polymerization of ε-caprolactone [23, 24]. It has been prepared as scaffolds by using salt-leaching and thermally induced phase separation techniques. However, these two methods are inconsistent and therefore are unsuitable for largescale production.
The properties of PCL depend on its molecular weight [25, 26]. High-molecular-weight PCL (80 kDa) is a white solid with a