3D Printing of High Viscosity Reinforced Silicone Elastomers

Abstract

Recent advances in additive manufacturing, specifically direct ink writing (DIW) and ink-jetting, have enabled the production of elastomeric silicone parts with deterministic control over the structure, shape, and mechanical properties. These new technologies offer rapid prototyping advantages and find applications in various fields, including biomedical devices, prosthetics, metamaterials, and soft robotics. Stereolithography (SLA) is a complementary approach with the ability to print with finer features and potentially higher throughput. However, all high-performance silicone elastomers are composites of polysiloxane networks reinforced with particulate filler, and consequently, silicone resins tend to have high viscosities (gel- or paste-like), which complicates or completely inhibits the layer-by-layer recoating process central to most SLA technologies. Herein, the design and build of a digital light projection SLA printer suitable for handling high-viscosity resins is demonstrated. Further, a series of UV-curable silicone resins with thiol-ene crosslinking and reinforced by a combination of fumed silica and MQ resins are also described. The resulting silicone elastomers are shown to have tunable mechanical properties, with 100–350% elongation and ultimate tensile strength from 1 to 2.5 MPa. Three-dimensional printed features of 0.4 mm were achieved, and complexity is demonstrated by octet-truss lattices that display negative stiffness.

Acoustophoretic Liquefaction for 3D Printing Ultrahigh‐Viscosity Nanoparticle Suspensions

“…As shown in Figure 2c, we see a rapid increase in relative viscosity (η r = μ/μ φ=0 ) at very modest volume fractions of filler (φ v < 0.1) at experimental shear rates. Like other composite resins based on silica, our measured rela tive viscosities greatly exceed the expected values of common rheological models by Einstein, Batchelor, and Kreiger-Dough erty [11,16,34] (see Table S3, Supporting Information for details). We attribute these orders of magnitude increase in relative vis cosity at low loading to the unique properties of silica.…”

Investigation on the Rheological Properties of Polydimethylsiloxane

“…The pace of applications of PDMS in the preparation of the membranes and filters is expected to accelerate as this polymer has shown appropriate properties in new rubbers [35][36][37][38][39][40][41][42]. Various materials have been investigated with previous applications in materials science, pure sciences, and engineering [43][44][45][46][47][48][49][50][51].…”

Additive manufacturing: Frameworks for chemical understanding and advancement in vat photopolymerization

“…For example, a common approach to making well-characterized materials like silicones printable in photo-based AM methods like SLA and DLP AM is to functionalize them with photo-reactive groups such as (meth)acrylates. 24 Acrylate groups can compromise the downstream material properties of the end-use objects, such as inducing lower mechanical strength and photo-induced aging effects compared to the base polymeric material. At the same time, the benefits of being able to print complex geometries and maintain some of the desired material properties, for example good biocompatibility and thermal insulation, make these compromises worth it for targeted applications.…”