## 3 Results and Discussion
Increasing the volume of the heated nozzle can decrease the possibility of a jam for PEEK filaments in the heated nozzle. According to the results proposed by [PERSON] et al. (2017) [22], the diameter of the heated nozzle is very important for the 3D printer based on the fused deposition modeling. A small diameter of the heated nozzle cannot make the PEEK move freely and easily form since the semi-liquid PEEK blocked the heated nozzle although the temperature of the heated nozzle was set higher than its melting point. Semi-liquid type PEEK then damages the heated nozzle for the 3D printer. In order to obtain the optimal diameter of the heated nozzle, various diameters of the heated nozzles, 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm, were tested. Diameters of the heated nozzle at 0.8 mm and 1.0 mm could not generate stalagmites at the heated nozzle. Poor 3D printing was observed using diameter 0.4 mm for the heated nozzle in our own 3D printer. Therefore, a diameter of 0.6 mm for the heated nozzle in our own 3D printer was employed for the preparation of PEEK samples. The part of the metal tube with a diameter of 2 mm connected with the heated nozzle can also inject PEEK filament smoothly into the heated nozzle compared with the original design of commercial 3D printer. Detailed comparisons of the original and new designs are shown in Figure 2. After we modified the designs of the heated nozzle and the metal tube, we got good PEEK disks using our 3D printer. Figure S1 in the Supplementary Materials shows the images of PEEK disks using the original and modified designs in our own 3D printer. In Figure S1I, a poor PEEK disk was obtained using the  
Figure 2: Summary of the original and new designs for the heated nozzle (**1**) and metal tube (**2**) used in this study. commerical 3D printer. After we modified the parameters and designs of our 3D printer, a uniform PEEK disk can be obtained (see Figure S1 II). Figure S2 also shows the surface and cross-sectional SEM images of the PEEK disks prepared using our modified 3D printer. A uniform PEEK sample without pinholes or voids can be observed in Figure S2I. In Figure S2 II, the fiber thicknesses of 600-900 nm were observed for PEEK disk. It indicates that our modifications are suitable for the production of PEEK samples using the 3D printer based on the fused modeling method. Therefore, these new designs were employed to prepare the PEEK disks for further tests. For the test of the antibacterial performances of PEEK samples, the target of this study is to obtain a PEEK sample with suitable antibacterial ability of around one month. Due to the poor absorption of antibiotic agents on the PEEK sample, PLGA was used as the binder of antibiotic agents and the control-release unit of antibiotic agents released into the buffer solution. When the PLGA contacts buffer solutions, the PLGA will decompose by hydrolysis of its ester linkages and produce lactic acid and glycolic acid and the antibiotic agents coated at the PEEK sample then release into the buffer solution. Table 1 shows the coating parameters for the various ratios of ampicillin/vancomycin on the PEEK substrates using the PLGA, which are the weight percent of ampicillin/total antibiotic agents of around 0%, 25%, 50%, 75%, and 100%. Drug release profiles for vancomycin and ampicillin from the samples into the buffer solution as a function of time in the 24-h test are shown in Figure S3I,II, respectively. From the results shown in Figure S3, both the drug release profiles of vancomycin and ampicillin were not stable and showed a peak profile for all samples in the first 6 h when the test began. The maximum drug release concentration for vancomycin and ampicillin of around 54 mg/L and 46 mg/L for samples (B) and (D) were observed, respectively. When the times for the tests were in the range of 7-24 h, the drug release profiles for ampicillin showed a stable increase with time for samples (B)-(E). However, the vancomycin release profiles for samples (C) and (D) decreased as a function of time. autocatalysis.