29 research outputs found
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UV-Photolithography Fabrication of Poly-Ethylene Glycol Hydrogels Encapsulated with Hepatocytes
The development of biomanufacturing technologies particularly, layered manufacturing has
advanced cell encapsulation processes in an effort to mimic the cellular microenvironment for invitro studies. This paper illustrates an inexpensive UV-photolithographic method for
encapsulation of human hepatocytes in three dimensional structures using poly-ethylene
diacrylate (PEGDA) hydrogels as candidate substrates. In order to further develop this
technology for layered fabrication, we have quantified the long-term effects of the photo-initiator
concentration and UV light exposure on the metabolic rates of encapsulated human hepatocytes
under a 21 day study. The photoinitator toxicity was observed immediately after polymerization
with no significant cytotoxicity on a long term basis. A cellular viability is examined and
reported for the UV photopolymerization process. Cell phenotype maintenance was observed by
measuring the amount of urea produced over a 1 week time period. This photo encapsulation
process may find use in the fabrication of spatially complex 3D scaffolds for tissue engineering
applications, elucidation of the 3D structure-pharmacokinetic response relationship and the
fabrication of complex multi-compartment liver tissue analog devices for drug screening
applications.Mechanical Engineerin
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Biomimetic Design and Fabrication of Interior Architecture of Tissue Scaffolds Using Solid Freeform Fabrication
Modeling, design and fabrication of tissue scaffolds with intricate architecture,
porosity and pore size for desired tissue properties presents a challenge in tissue engineering.
This paper will present the details of our development in designing and fabrication of the
interior architecture of scaffolds using a novel design approach. The Interior Architecture
Design (IAD) approach seeks to generate scaffold layered freeform fabrication tool path without
forming complicated 3D CAD scaffold models. This involves: applying the principle of layered
manufacturing to determine the scaffold individual layered process planes and layered contour;
defining the 2D characteristic patterns of the scaffold building blocks (unit cells) to form the
Interior Scaffold Pattern; and the generation of process tool path for freeform fabrication of
these scaffolds with the specified interior architecture. Feasibility studies applying the IAD
algorithm to example models and the generation of fabrication planning instructions will be
presented.Mechanical Engineerin
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Layered Fabrication of Branched Networks Using Lindenmayer Systems
A current challenge impeding the growth of bone tissue engineering is the lack of
functional scaffolds of geometric sizes greater than 10mm due to the inability of cells to
survive deep within the scaffold. It is hypothesized that these scaffolds must have an
inbuilt nutrient distribution network to sustain the uniform growth of cells. In this
paper, we seek to enhance the design and layered fabrication of scaffold internal
architecture through the development of Lindenmayer systems, a graphical language
based theory to create nutrient delivery networks. The scaffolds are fabricated using the
Texas Instruments DLPâą system through UVâphotopolymerization to produce
polyethylene glycol hydrogels with internal branch structures. The paper will discuss
the Lindenmayer system, process planning algorithms, layered fabrication of samples,
challenges and future tasks.Mechanical Engineerin
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Freeform Bioprinting of Liver Encapsulated in Alginate Hydrogels Tissue Constructs for Pharmacokinetic Study
An in vitro model that can be realistically and inexpensively used to predict human response to
various drug administration and toxic chemical exposure is needed. By fabricating a microscale
3D physiological tissue construct consisting of an array of channels and tissue-embedded
chambers, one can selectively develop various biomimicking mammalian tissues for a number of
pharmaceutical applications, for example, experimental pharmaceutical screening for drug
efficacy and toxicity along with apprehending the disposition and metabolic profile of a
candidate drug. This paper addresses issues relating to the development and implementation of a
bioprinting process for freeform fabrication of a 3D cell-encapsulated hydrogel-based tissue
construct, the direct integration onto a microfluidic device for pharmacokinetic study, and the
underlying engineering science for the fabrication of a 3D microscale tissue chamber as well as
its application in pharmacokinetic study. To this end, a prototype 3D microfluidic tissue chamber
embedded with liver cells encapsulated within a hydrogel matrix construct is bioprinted as a
physiological in vitro model for pharmacokinetic study. The developed fabrication processes are
further validated and parameters optimized by assessing cell viability and liver cell phenotype, in
which metabolic and synthetic liver functions are quantitated.Mechanical Engineerin
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Direct Slicing of STEP Based NURBS Models for Solid Freeform Fabrication
Direct slicing of CAD models to generate process planning instructions for solid freeform
fabrication may overcome inherent disadvantages of using STL format in terms of the process
accuracy, ease of file management, and incorporation of multiple materials. This paper will
present the results of our development of a direct slicing algorithm for layered freeform
fabrication. The direct slicing algorithm was based on a neutral, international standard (ISO
10303) STEP-formatted NURBS geometric representation and is intended to be independent of
any commercial CAD software. The following aspects of the development effort will be
presented: 1) Determination of optimal build direction based upon STEP-based NURBS models;
2) Adaptive subdivision of NURBS data for geometric refinement; and 3) Ray-casting slice
generation into sets of raster patterns. Feasibility studies applying the direct slicing algorithm to
example models and the generation of fabrication planning instructions involving multi-material
structures will also be presented.Mechanical Engineerin
Direct slicing of STEP based NURBS models for layered manufacturing
Abstract Direct slicing of CAD models to generate process planning instructions for solid freeform fabrication may overcome inherent disadvantages of using stereolithography format in terms of the process accuracy, ease of file management, and incorporation of multiple materials. This paper will present the results of our development of a direct slicing algorithm for layered freeform fabrication. The direct slicing algorithm was based on a neutral, international standard (ISO 10303) STEP-formatted non-uniform rational B-spline (NURBS) geometric representation and is intended to be independent of any commercial CAD software. The following aspects of the development effort will be presented: (1) determination of optimal build direction based upon STEP-based NURBS models; (2) adaptive subdivision of NURBS data for geometric refinement; and (3) ray-casting slice generation into sets of raster patterns. The development also provides for multi-material slicing and will provide an effective tool in heterogeneous slicing processes.
Computer-aided characterization of effective mechanical properties for porous tissue scaffolds
porous tissue scaffold
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Layered Composite Model for Design and Fabrication of Bone Replacement
Biological tissues are inherently heterogeneous. The design of 3D tissue scaffolds for tissue
engineering application should, if possible, biomimic the complex hierarchy and structural
heterogeneity of the replaced tissues. This is particularly true for design of bone scaffolds with
structural properties compatible with the spatial heterogeneity and mechanical properties of the
replaced tissue. The paper presents an image-based computer modeling approach for
reconstruction, characterization, and biomimetic modeling and design of three-dimensional
heterogeneous tissue structure. The presented work will cover: 1) overview of biomimetic
modeling and design of bone structures and reverse engineering for CAD-based constructive
solid geometry; 2) design of bone scaffold; and 3) slicing and process planning for solid freeform
fabricationWe gratefully acknowledge support from NSF CRCD-9980298 and support from Therics,
Inc.Mechanical Engineerin
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Scalable Linking of Slice Layer Information with Process Monitoring Data in Additive Manufacturing Machines
In smart connected factories, manufacturing machines are capable of generating vast amounts of
process data generated internally from within its control systems or from sensors coupled with the
process. This streaming data must be stored and queried to perform data analytics or closed loop
control to improve manufacturing processes. Currently, structured data schemas are ineffective in
handling image and time-series data generated from additive manufacturing machines. In this
paper, we propose an unstructured data schema through NoSQL document oriented database
systems as an effective and scalable approach to capturing and storing real-time streaming data for
process monitoring. In addition, we present an approach to linking in real-time, slice layer
information and tag it with process related sensor data for performing fast, scalable queries either
in real-time or post-fabrication. We have demonstrated our approach with two classes of additive
manufacturing machines â Fused Deposition Modeling and Electron Beam Melting Systems from
Makerbot and ARCAM respectively.Mechanical Engineerin