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

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

Modifications to commercial printers to enable multi-material fabrication of 3D cellular scaffolds

The scarcity of organs for patients that need transplants has led to exceedingly lengthy waits for organ transplants for sick patients. Fabrication of tissues and organ constructs in-vitro has potential to end the shortage, however many of the machines used to create these tissues and organs are expensive, not easy to use, and do not have any further practical applications. Bioprinting technology has the potential to revolutionize the fabrication of biological constructs that can be used as in vitro model tissues and vivo substitutes. Bioprinting is the process of using conventional 3D printing methods and computer-aided-design (CAD) to create patient and user specific constructs with biological material. 3D printers are ideal for low volume customizable parts, and when these parts can be made of living cells and biomaterials these machines become ideal for cell based research. Converting commercially available 3D printers into biomanufacturing units answers several problems that are faced by researchers, namely: the ability to create 3D multicomponent system creating multicellular interfaces in cell culture, and the ability to study cells in a true 3D environment. Although biological tissues have a range of cell types and material properties, current bioprinting methods are limited in their ability to print multiple materials simultaneously, especially tissues with vastly different material properties. For instance, printing of soft gels alongside a hard-structural material remains a challenge, as the thermal, mechanical, and biochemical parameters during the printing process must be maintained in an appropriate range to ensure high viability of living cells. Therefore, to truly realize the potential of bioprinting within the biomedical community, new capabilities that allow multi-material bioprinting are needed. The goal of this work is to enable four capabilities using commercially available inexpensive 3D printers: (i) printing of new thermoplastics, (ii) printing of structural thermoplastic material alongside soft biomaterials (iii) printing two soft biomaterials and/or cell types using conventional extrusion printing, and (iv) printing soft biomaterials that do not possess the necessary material properties for conventional extrusion printing. Results from this work will democratize bioprinting technology by driving down the cost of entry into the field, and will enable its use in solving important challenges in the field of tissue engineering

Procedural function-based modelling of volumetric microstructures

We propose a new approach to modelling heterogeneous objects containing internal volumetric structures with size of details orders of magnitude smaller than the overall size of the object. The proposed function-based procedural representation provides compact, precise, and arbitrarily parameterised models of coherent microstructures, which can undergo blending, deformations, and other geometric operations, and can be directly rendered and fabricated without generating any auxiliary representations (such as polygonal meshes and voxel arrays). In particular, modelling of regular lattices and cellular microstructures as well as irregular porous media is discussed and illustrated. We also present a method to estimate parameters of the given model by fitting it to microstructure data obtained with magnetic resonance imaging and other measurements of natural and artificial objects. Examples of rendering and digital fabrication of microstructure models are presented

3D microfabrication of biological machines

The burgeoning field of additive manufacturing, or “3D printing”, centers on the idea of creating three-dimensional objects from digital models. While conventional manufacturing approaches rely on modifying a base material via subtractive processes such as drilling or cutting, 3D printing creates three-dimensional objects through successive deposition of two- dimensional layers. By enabling rapid fabrication of complex objects, 3D printing is revolutionizing the fields of engineering design and manufacturing. This thesis details the development of a projection-based stereolithographic 3D printing apparatus capable of high- resolution patterning of living cells and cell signals dispersed in an absorbent hydrogel polymer matrix in vitro. This novel enabling technology can be used to create model cellular systems that lead to a quantitative understanding of the way cells sense, process, and respond to signals in their environment. The ability to pattern cells and instructive biomaterials into complex 3D patterns has many applications in the field of tissue engineering, or “reverse engineering” of cellular systems that replicate the structure and function of native tissue. While the goal of reverse engineering native tissue is promising for medical applications, this idea of building with biological components concurrently brings about a new discipline: “forward engineering” of biological machines and systems. In addition to rebuilding existing systems with cells, this technology enables the design and forward engineering of novel systems that harness the innate dynamic abilities of cells to self-organize, self-heal, and self-replicate in response to environmental cues. This thesis details the development of skeletal and cardiac muscle based bioactuators that can sense external electrical and optical signals and demonstrate controlled locomotive behavior in response to them. Such machines, which can sense, process, and respond to signals in a dynamic environment, have a myriad array of applications including toxin neutralization and high throughput drug testing in vitro and drug delivery and programmable tissue engineered implants in vivo. A synthesis of two fields, 3D printing and tissue engineering, has brought about a new discipline: using microfabrication technologies to forward engineer biological machines and systems capable of complex functional behavior. By introducing a new set of “building blocks” into the engineer’s toolbox, this new era of design and manufacturing promises to open up a field of research that will redefine our world

Design and Fabrication of Components with Optimized Lattice Microstructures

The design and fabrication of components with optimized lattice microstructures is a new approach to creating lightweight high-performance objects. This paper introduces a unique and complete integration of design and fabrication leading to the creation of structural components with complex composite microstructures. Rather than a solid cast component with optimized outer shape this new approach leads to a component with an inner skeleton or microstructure maximizing one or more properties such as the stiffness-to-weight ratio. Three dimensional gradient materials are a natural outcome of this approach. An introduction to the design optimization and hybrid fabrication approach will be provided in addition to research progress and challenges through Spring 2004.Mechanical Engineerin

Part 2: pushing the envelope. A process perspective for architecture, engineering and construction

In this article, I am building on an emerging 'process view of nature' and how biological membranes emerge through the combined action of (locally) autonomous construction agents. In Part 1, we considered the simultaneous aggregation and disaggregation of matter around embedded processes, used to create, sustain and regulate matter, energy and information gradients from which 'work' is derived for the benefit of the agents or organisms present in the system. In Part 2, I intend to demonstrate that emerging digital design, simulation and fabrication techniques, when linked to sensory and effector feedback, memory and actions, directed by pre-encoded objectives (as rules or algorithms), produce the same fundamental unit of 'agency' as biological agents possess. By understanding how biological membranes emerge in nature, as the outcome of 'negotiated agency', to regulate matter, energy and information exchange between adjacent spaces, we can begin to consider the building envelope as a biological interface or membrane from which 'work' can be derived from the environment we inhabit, as a physiological extension of ourselves

Adaptive locomotion of artificial microswimmers

Bacteria can exploit mechanics to display remarkable plasticity in response to locally changing physical and chemical conditions. Compliant structures play a striking role in their taxis behavior, specifically for navigation inside complex and structured environments. Bioinspired mechanisms with rationally designed architectures capable of large, nonlinear deformation present opportunities for introducing autonomy into engineered small-scale devices. This work analyzes the effect of hydrodynamic forces and rheology of local surroundings on swimming at low Reynolds number, identifies the challenges and benefits of utilizing elastohydrodynamic coupling in locomotion, and further develops a suite of machinery for building untethered microrobots with self-regulated mobility. We demonstrate that coupling the structural and magnetic properties of artificial microswimmers with the dynamic properties of the fluid leads to adaptive locomotion in the absence of on-board sensors

Research Towards High Speed Freeforming

Additive manufacturing (AM) methods are currently utilised for the manufacture of prototypes and low volume, high cost parts. This is because in most cases the high material costs and low volumetric deposition rates of AM parts result in higher per part cost than traditional manufacturing methods. This paper brings together recent research aimed at improving the economics of AM, in particular Extrusion Freeforming (EF). A new class of machine is described called High Speed Additive Manufacturing (HSAM) in which software, hardware and materials advances are aggregated. HSAM could be cost competitive with injection moulding for medium sized medium quantity parts. A general outline for a HSAM machine and supply chain is provided along with future required research