# 3D Printed Antibacterial Prostheses
## 2 Materials and Methods
### 3D Printed Antibacterial Finger Prosthesis Description  
The 3D printed antibacterial finger prosthesis was a voluntary-closing prosthesis powered by metacarpophalangeal (MCP) flexion. A detailed technical drawing and rendering of the finger design can be found in Figure 2 (Figure 2A-C). The device was secured using a customized neoprene strap in the palm of the hand. The prosthesis was designed to be proportional to the length and circumference of the participant's non-affected finger. The 3D printed antibacterial finger prosthesis allowed pinch grasping actions actuated by flexion of the MCP. A MCP flexion of 40\({}^{\circ}\) produced 1 inch of cable travel for full operation. A silicone finger grip was added onto the fingertip to increase friction and to prevent slippage of gripped objects. The scaling of the prosthesis was performed remotely and began with instructing the patient to photograph both the affected and unaffected limbs including a known measurable scale, such as metric grid paper (Figure 1A). This photogrammetric method allowed the extraction of several anthropometric measurements from the photographs. This photo was then uploaded to Autodesk Fusion 360 and used as a backdrop. The software measuring system was calibrated with the ruler included in the photograph. Once the prosthesis had been scaled to the patient's arm and measurements had been confirmed by a certified prosthetist, the files were uploaded to a desktop 3D Printer (Ultimaker 2 extended, Ultimaker B.V., Geldermalsen, The Netherlands). The prosthesis was manufactured using PLACTIVETM (PLACTIVETM 1% Antibacterial Nanoparticles additive, Copper3D, Santiago, Chile), which is a high quality polylactic acid polymer, using an internationally patented additive containing copper nanoparticles. Copper nanoparticles have been showed to be effective in eliminating fungi, viruses, and bacteria, but are harmless to humans. PLACTIVETM was chosen as it uses a sound and proven antibacterial mechanism, is a low-cost material that is biodegradable, and possesses thermoforming characteristics that facilitate post-processing and final adjustments of 3D printed prostheses. PLACTIVETM has similar physical (relative viscosity = 4.0 g/dL, clarity = transparent, peak melt temperature = 145-160 \({}^{\circ}\)C, glass transition temperature = 55-60 \({}^{\circ}\)C) and mechanical (tensile yield strength = 8700 psi, tensile strength at break = 7700 psi, tensile modulus = 524,000 psi, tensile elongation = 6%, flexural strength = 12,000 psi, and heat distortion temperature at 66 psi = 55 \({}^{\circ}\)C) properties to standard polylactic acid filaments.  
The average printing time for the 3D printed finger prostheses was 60 \(\pm\) 5.6 min. The cost of a 750 g spool of antibacterial filament is $92 USD. All parts were printed at 40% infill (hexagon pattern) with a 50 mm/s print speed and a 150-200 mm/s travel speed on a 50 \({}^{\circ}\)C heated bed at a printing temperature of 200 \({}^{\circ}\)C with a 0.15 mm layer height and 1 mm shell thickness. Post-processing consisted of support removal and filing of rough areas in the joints and prosthetic socket area in contact with the skin. The location and generation of the support as well as the build orientation on the building platform are illustrated in Figure 3. The post-processing of the 3D printed antibacterial prosthesis took 10 min, and assembly took 30 min.