3,668 research outputs found
Development of a 3D printer using scanning projection stereolithography
We have developed a system for the rapid fabrication of low cost 3D devices and systems in the laboratory with micro-scale features yet cm-scale objects. Our system is inspired by maskless lithography, where a digital micromirror device (DMD) is used to project patterns with resolution up to 10 µm onto a layer of photoresist. Large area objects can be fabricated by stitching projected images over a 5cm2 area. The addition of a z-stage allows multiple layers to be stacked to create 3D objects, removing the need for any developing or etching steps but at the same time leading to true 3D devices which are robust, configurable and scalable. We demonstrate the applications of the system by printing a range of micro-scale objects as well as a fully functioning microfluidic droplet device and test its integrity by pumping dye through the channels
Recent advances in 3D printing of biomaterials.
3D Printing promises to produce complex biomedical devices according to computer design using patient-specific anatomical data. Since its initial use as pre-surgical visualization models and tooling molds, 3D Printing has slowly evolved to create one-of-a-kind devices, implants, scaffolds for tissue engineering, diagnostic platforms, and drug delivery systems. Fueled by the recent explosion in public interest and access to affordable printers, there is renewed interest to combine stem cells with custom 3D scaffolds for personalized regenerative medicine. Before 3D Printing can be used routinely for the regeneration of complex tissues (e.g. bone, cartilage, muscles, vessels, nerves in the craniomaxillofacial complex), and complex organs with intricate 3D microarchitecture (e.g. liver, lymphoid organs), several technological limitations must be addressed. In this review, the major materials and technology advances within the last five years for each of the common 3D Printing technologies (Three Dimensional Printing, Fused Deposition Modeling, Selective Laser Sintering, Stereolithography, and 3D Plotting/Direct-Write/Bioprinting) are described. Examples are highlighted to illustrate progress of each technology in tissue engineering, and key limitations are identified to motivate future research and advance this fascinating field of advanced manufacturing
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Compensation Zone Approach to Avoid Z Errors in Mask Projection Stereolithography Builds
Print-through results in unwanted polymerization occurring beneath a part cured using
Mask Projection Stereolithography (MPSLA) and thus creates error in its Z dimension. In this
paper, the "Compensation zone approach" is proposed to avoid this error. This approach entails
modifying the geometry of the part to be cured. A volume (Compensation zone) is subtracted
from underneath the CAD model in order to compensate for the increase in the Z dimension that
would occur due to Print-through. Three process variables have been identified: Thickness of
Compensation zone, Thickness of every layer and Exposure distribution across every image used
to cure a layer. Analytical relations have been formulated between these process variables in
order to obtain dimensionally accurate parts. The Compensation zone approach is demonstrated
on an example problem.Mechanical Engineerin
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Quantifying Dimensional Accuracy of a Mask Projection Micro Stereolithography System
Mask Projection Microstereolithography is capable for fabricating true three-dimensional
microparts and hence, holds promise as a potential micro-fabrication process for micro-machine
components. In this paper, the Mask Projection Micro-Stereolithography (MPµSLA) system
developed at the Rapid Prototyping and Manufacturing Institute at Georgia Institute of
Technology is presented. The dimensional accuracy of the system is improved by reducing its
process planning errors. To this effect, the MPµSLA process is mathematically modeled. In this
paper, the irradiance received by the resin surface is modeled as a function of the imaging system
parameters and the pattern displayed on the dynamic mask. The resin used in the system is
characterized to experimentally determine its working curve. This work enables us to compute
the dimensions of a single layer cured using our system. The analytical model is validated by
curing test layers on the system. The model computes layer dimensions within 5% error.Mechanical Engineerin
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On the Use of Angled, Dynamic Laser Beams to Improve Stereolithography Surface Finish
Improved surface finish of Stereolithography (SLA) parts is an important goal for furthering
the resolution of the technology. In order to improve the surface finish, a dynamic laser beam
with changing angle, beam size, beam shape, and irradiance distribution is proposed. In this
paper, an analytical irradiance model of an angled, dynamic laser beam in the SLA process is
presented. This model is used to simulate cured shapes of SLA builds. Simulated build shapes
are compared to established SLA analytical models and conclusions are drawn on the accuracy
of the developed model.Mechanical Engineerin
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Nanotailoring Stereolithography Resins for Unique Applications using Carbon Nanotubes
Nanostructured materials and exploiting their properties in stereolithography (SL) may open
new markets for unique rapidly manufactured functional devices. Controlled amounts of multiwalled carbon nanotubes (MWCNTs) were successfully dispersed in SL epoxy-based resins and
complex three-dimensional (3D) parts were successfully fabricated by means of a multi-material
SL setup. The effect of the nanosized filler was evaluated using mechanical testing. Small
dispersions of MWCNTs resulted in significant effects on the physical properties of the
polymerized resin. A MWCNT concentration of .05 wt% (w/v) in DSM Somos® WaterShed™
11120 resin increased the ultimate tensile stress and fracture stress an average of 17% and 37%,
respectively. Electron microscopy was used to examine the morphology of the nanocomposite
and results showed affinity between the MWCNTs and SL resin and identified buckled
nanotubes that illustrated strong interfacial bonding. These improved physical properties may
provide opportunities for using nanocomposite SL resins in end-use applications. Varying types
and concentrations of nanomaterials can be used to tailor existing SL resins for particular
applications.Mechanical Engineerin
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Multi-Material Stereolithography: Spatially-Controlled Bioactive Poly(Ethylene Glycol) Scaffolds for Tissue Engineering
Challenges remain in tissue engineering to control the spatial and temporal mechanical and
biochemical architectures of scaffolds. Unique capabilities of stereolithography (SL) for
fabricating multi-material spatially-controlled bioactive scaffolds were explored in this work. To
accomplish multi-material builds with implantable materials, a new mini-vat setup was designed,
constructed and placed on top of the existing build platform to allow for accurate and selfaligning X-Y registration during fabrication. Precise quantities of photocrosslinkable solution
were added to and removed from the mini-vat using micro-pipettes. The mini-vat setup allowed
the part to be easily removed and rinsed and different photocrosslinkable solutions could be
easily removed and added to the vat to aid in multi-material fabrication. Two photocrosslinkable
hydrogel biopolymers, poly(ethylene glycol dimethacrylate) (PEG-dma, molecular wt 1,000) and
poly(ethylene glycol)-diacrylate (PEG-da, molecular wt 3,400), were used as the primary
scaffold materials, and controlled concentrations of fluorescently labeled dextran or bioactive
PEG were prescribed and fabricated in different regions of the scaffold using SL. The
equilibrium swelling behavior of the two biopolymers after SL fabrication was determined and
used to design constructs with the specified dimensions at the swollen state. Two methods were
used to measure the spatial gradients enabled by this process with multi-material spatial control
successfully demonstrated down to 500-µm. First, the presence of the fluorescent component in
specific regions of the scaffold was analyzed with fluorescent microscopy. Second, human
dermal fibroblast cells were seeded on top of the fabricated scaffolds with selective bioactivity,
and phase contrast microscopy images were used to show specific localization of cells in the
regions patterned with bioactive PEG. The use of multi-material SL and the relative ease of
conjugating different bioactive ligands or growth factors to PEG allows for the fabrication of
tailored three-dimensional constructs with specified spatially-controlled bioactivity.Mechanical Engineerin
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Numerical Study on the Recoating Process in Microstereolithography
Microstereolithography is a promising RP-based micro-fabrication technique that aims to
meet the demands for complex geometry micro-scale parts. Projection microstereolithography
incorporates a Dynamic Pattern Generator to obtain high resolution in the parallel plane.
However, its lateral resolution has been always limited by the final layer thickness and the long
resin settling time, both of which rely on the recoating process. In order to find the critical
factors behind the recoating process, a numerical simulation method (Computational Fluid
Dynamics, CFD) has been used to investigate the relationships among final layer thickness,
settling time, resin viscosity and ratio of object/container size. These results are helpful for the
selection of resin characteristics and the design of the microstereolithography machine.Mechanical Engineerin
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Hydrogels in Stereolithography
The use of stereolithography (SL) for fabricating complex three-dimensional (3D) tissue
engineered scaffolds of aqueous poly(ethylene glycol) (PEG) hydrogel solutions is described.
The primary polymer used in the study was PEG-dimethacrylate (PEG-dma) with an average
molecular weight (MW) of 1000 in distilled water with the photoinitiator Irgacure 2959 (I-2959).
Successful layered manufacturing (LM) with embedded channel architecture required
investigation of the photopolymerization characteristics of the PEG solution (measured as
hydrogel thickness or cure depth) as a function of photoinitiator concentration and laser energy
dosage for a specific photoinitiator type and polymer concentration in solution. Hydrogel
thickness was a strong function of PI concentration and energy dosage. Curves of hydrogel
thickness were utilized to successfully plan, perform, and demonstrate layered manufacturing of
highly complex hydrogel scaffold structures, including structures with internal channels of
various orientations. Successful fabrication of 3D, multi-layered bioactive PEG scaffolds
containing cells was accomplished using a slightly modified commercial SL system (with 325
nm wavelength laser) and procedure. Human dermal fibroblast (HDF) cells were encapsulated in
PEG hydrogels using small concentrations (~ 5 mg/ml) of acryloyl-PEG-RGDS (MW 3400)
added to the photopolymerizable PEG solution to promote cell attachment. HDF cells were
combined with the PEG solution, photocrosslinked using SL, and successfully shown to survive
the fabrication process. The combined use of SL and photocrosslinkable biomaterials such as
PEG makes it possible to fabricate complex 3D scaffolds that provide site-specific and tailored
mechanical properties (i.e., multiple polymer materials) with a polymer matrix that allows
transport of nutrients and waste at the macroscale and facilitates cellular processes at the
microscale through precisely placed bioactive agents.Mechanical Engineerin
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