D Printed Components
All electrodes (other than the stainless steel meshes) and housing components were first modeled in Autodesk Inventor, exported in .stl format and 3D printed by fused deposition modeling (FDM). See Sect. 1.4 for details of the FDM process. Electrodes were printed in a polyethylene terephthalate glycol copolymer (PETG) sold under the name 3DXNano ESD PETG (3DXTech, MI, USA). The filament contains a dispersion of multi-walled carbon nanotubes (MWCNTs) which serve to provide a slight conductivity to the PETG. According to the manufacturer, surface conductivity of the final 3D printed components generally falls in the range of 107109 X/square. This range of conductivity is normally associated with materials made for applications in which electrostatic discharging (ESD) is a necessity. Electrodes were printed on a modified Makerfarm Prusa i3v (Makerfarm, UT, USA). The modifications were made to improve print quality and to permit direct-drive extrusion with an E3D v5 all-metal hot end (E3D, Oxfordshire, UK). For the manufacture of electrodes, the hot end was fit with a 0.25 mm brass nozzle. All non-conductive components were printed in a polylactide/polyhydrox- yalkanoate (PLA/PHA) blend (Colorfabb, Venlo, Netherlands) on the same Makerfarm Prusa i3v. All housing and non-conductive components were printed using a 0.4 mm nozzle.
G-code was generated from .stl files in Slic3r version 1.2.9. General slicer settings for conductive PETG components were: 0.16 mm layer heights, 3 perimeters loops, 20% hexagonal infill, 250 °C extrusion temperature, and 80 °C bed temperature. All parts printed in PLA/PHA were printed at 0.2 mm layer height, 3 perimeters, 25% rectilinear infill, 195 °C extrusion temperature, and 70 °C bed temperature. Both materials were printed onto a glass bed coated with a layer of polyimide tape that was wiped clean with acetone to remove oils and any other contaminants.