Thermally cured thermoset polymers such as epoxies are widely used in industry and manufacturing due to their thermal, chemical, and electrical resistance, and mechanical strength and toughness. However, it can be challenging to 3D print thermally cured thermosets without rheological modification because they tend to flow and not hold their shape when extruded due to cure times of minutes to hours. 3D printing inside a support bath addresses this by allowing the liquid polymer to be held in place until the thermoset is fully cured and expands the structures that can be printed as extrusion is not limited to layer‐by‐layer. Here, the use of Freeform Reversible Embedding (FRE) to 3D print off‐the‐shelf thermoset epoxy into lattice structures using nonplanar extrusion is reported. To do this, the authors investigate how extrusion direction in 3D space impacts epoxy filament morphology and fusion at filament intersections. Furthermore, the advantages of this approach are shown by using nonplanar printing to produce lattice geometries that show ≈ four times greater specific modulus compared with lattice structures printed using other materials and printing techniques.
Degenerative disc disease (DDD) is the leading cause of low back pain and radiating leg pain. DDD is commonly treated surgically using spinal fusion techniques, but in many cases failure occurs due to insufficient immobilization of the vertebrae during fusion. The fabrication and demonstration of a 3D‐printed semi‐crystalline liquid crystal elastomer (LCE) spinal fusion cage that addresses these challenges in particular subsidence are described. During implantation of the fusion cage, the LCE is rubbery and capable of deforming around and conforming to delicate anatomy. In the hours following implantation, the device crystallizes into a rigid, structural material with the modulus increasing tenfold from 8 to 80 MPa. In the crystalline regime, a 3D‐printed prototype device is capable of enduring 1 million cycles of physiologic compressive loading with minimal creep‐induced ratcheting. Effects of LCE molecular architecture on the rate and magnitude of modulus increase, material processability, and mechanical properties are explored. This fundamental characterization informs a proof‐of‐concept device—the first bulk 3D printed LCE demonstrated to date. Moreover, the novel deployment strategy represents an exciting new paradigm of spinal fusion cages, which addresses real clinical challenges in expandable interbody fusion cages.
more » « less- NSF-PAR ID:
- 10458756
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Healthcare Materials
- Volume:
- 9
- Issue:
- 1
- ISSN:
- 2192-2640
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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