Polydimethylsiloxane
(PDMS) elastomer is used in a wide range of
biomaterial applications including microfluidics, cell culture substrates,
flexible electronics, and medical devices. However, it has proved
challenging to 3D print PDMS in complex structures due to its low
elastic modulus and need for support during the printing process.
Here we demonstrate the 3D printing of hydrophobic PDMS prepolymer
resins within a hydrophilic Carbopol gel support via freeform reversible
embedding (FRE). In the FRE printing process, the Carbopol support
acts as a Bingham plastic that yields and fluidizes when the syringe
tip of the 3D printer moves through it, but acts as a solid for the
PDMS extruded within it. This, in combination with the immiscibility
of hydrophobic PDMS in the hydrophilic Carbopol, confines the PDMS
prepolymer within the support for curing times up to 72 h while maintaining
dimensional stability. After printing and curing, the Carbopol support
gel releases the embedded PDMS prints by using phosphate buffered
saline solution to reduce the Carbopol yield stress. As proof-of-concept,
we used Sylgard 184 PDMS to 3D print linear and helical filaments
via continuous extrusion and cylindrical and helical tubes via layer-by-layer
fabrication. Importantly, we show that the 3D printed tubes were manifold
and perfusable. The results demonstrate that hydrophobic polymers
with low viscosity and long cure times can be 3D printed using a hydrophilic
support, expanding the range of biomaterials that can be used in additive
manufacturing. Further, by implementing the technology using low cost
open-source hardware and software tools, the FRE printing technique
can be rapidly implemented for research applications.
Syringe pump extruders are required for a wide range of 3D printing applications, including bioprinting, embedded printing, and food printing. However, the mass of the syringe becomes a major challenge for most printing platforms, requiring compromises in speed, resolution and/or volume. To address these issues, we have designed a syringe pump large volume extruder (LVE) that is compatible with low-cost, open source 3D printers, and herein demonstrate its performance on a PrintrBot Simple Metal. Key aspects of the LVE include: (1) it is open source and compatible with open source hardware and software, making it inexpensive and widely accessible to the 3D printing community, (2) it utilizes a standard 60 mL syringe as its ink reservoir, effectively increasing print volume of the average bioprinter, (3) it is capable of retraction and high speed movements, and (4) it can print fluids using nozzle diameters as small as 100 µm, enabling the printing of complex shapes/objects when used in conjunction with the freeform reversible embedding of suspended hydrogels (FRESH) 3D printing method. Printing performance of the LVE is demonstrated by utilizing alginate as a model biomaterial ink to fabricate parametric CAD models and standard calibration objects.
Additive manufacturing promises a major transformation of the production of high economic value metallic materials, enabling innovative, geometrically complex designs with minimal material waste. The overarching challenge is to design alloys that are compatible with the unique additive processing conditions while maintaining material properties sufficient for the challenging environments encountered in energy, space, and nuclear applications. Here we describe a class of high strength, defect-resistant 3D printable superalloys containing approximately equal parts of Co and Ni along with Al, Cr, Ta and W that possess strengths in excess of 1.1 GPa in as-printed and post-processed forms and tensile ductilities of greater than 13% at room temperature. These alloys are amenable to crack-free 3D printing via electron beam melting (EBM) with preheat as well as selective laser melting (SLM) with limited preheat. Alloy design principles are described along with the structure and properties of EBM and SLM CoNi-base materials.
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