MULTI-INK 3D PRINTING OF UV-CURABLE SILICONES

Abstract

Silicones are an important implant material, and as additive manufacturing technologies are revolutionizing many fields, one interesting application is the production of patient-specific silicone bio-implants where the stiffness of the material may not be homogenous over the entire part. 3D printing technology is well suited for construction of such custom parts. However, current 3D printing methods for silicone are not capable of printing multiple materials to mimic the heterogeneous properties of real tissue. The objective of this thesis is the development of additive manufacturing method for silicone objects with multiple constituent inks. To this end, a pneumatic 3D printer to print multiple silicone UV-curable inks based on thiol-ene chemistry was developed. The effect of parameters such as nozzle diameter, applied pressure, feedrate and Z offset on the ink deposition process was investigated and optimized printing conditions determined. The results showed that a successful creation of a continuous ink trace depends on correlating these parameters, a simple model for this correlation is presented. By optimizing parameters, traces of 600µm in width and 80µm in height were produced. Another key factor for the trace dimensions and for preventing clogging failures was found to be the UV illumination pattern in the vicinity of the nozzle. By optimizing exposure, continuous printing for 30 mins was demonstrated. The complete system was shown capable of printing 3D objects composed of three different silicone inks with capabilities such as disconnected feature printing, printing of overhangs and two modes of ink switching. Such a printer can be potentially applied in the fabrication of custom implants, production of meta-materials and bio-printing.