2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Applications: Biomedical
Program Organizers: Joseph Beaman, University of Texas at Austin
Wednesday 8:00 AM
August 14, 2024
Room: 417 AB
Location: Hilton Austin
Session Chair: Maryam Tilton, University of Texas at Austin
8:00 AM
A Post Processing Technique to Achieve Nanofinishing and Biocompatibility Enhancement of
Ti-6Al-4V Femoral Head Fabricated by Laser Powder Bed Fusion: Atul Rajput1; Sajan Kapil2; Manas Das2; 1IITG TIDF; 2Indian Institue of Technology Guwahati
Ti-6Al-4V alloys are extensively used as a substitution for human bones as they are biocompatible, lightweight, corrosive resistant, and have low elastic modulus. Additive Manufacturing is the best suitable process for realizing complex biomedical implants of Ti-6Al-4V alloys. However, some implants require a mirror-like polished surface typically obtained through a post-processing technique. Therefore, this work proposed a post-processing method to improve the surface quality of additively manufactured Ti-6Al-4V alloys. Hybrid Electrochemical Assisted Magnetorheological utilizes the synergic action of mechanical abrasion and electrochemical reaction to enhance the surface quality of the parts without affecting their surface topography. However, the H-ECMR finishing process effectively applies to parts with initial Ra in the sub-micron range. Hence, chemical etching is used as an intermediate process after fabricating the femoral head by LPBF to reduce the surface roughness in the sub-micron range. A final surface roughness of 33.14 nm is achieved on the polished surface.
8:20 AM
Decision-Making Framework for Customized Additively-Manufactured Lower-Limb Prosthetics: Isha Gujarathi1; ZJ Pei1; Maryam Zahabi1; Albert Patterson1; 1Texas A&M University
This work gives an overview of a novel decision-making process for designing additively-manufactured thermoplastic lower-limb prosthetics. The framework is based on analytical hierarchy process (AHP) decision making, where patient information, stakeholder (doctor, patient, others) wishes, and realistic manufacturability constraints using AM are all considered. Instead of a process where a single design or alternative is selected, the AHP method allows the stakeholders to rank and simultaneously evaluate several close or imperfect options for design. A usable tool written in MS Excel and Python is provided, along with a tutorial for use in realistic scenarios. This will be supported by a detailed long-form case study which includes the design and prototyping of several design alternatives using both primitive shape design and topology optimization. Patient data for the case study was taken from published literature sources, so no human subjects were directly used for this project and IRB approval was not necessary.
8:40 AM
Establishing a Pipeline for the Scanning, Editing, and Full-color Additive Manufacturing of Cadavers for Anatomy Training: Nicholas Meisel1; Evan Goldman2; 1Pennsylvania State University; 2Penn State Health
Gross anatomy dissection is often seen as the ideal standard for anatomy education. However, gaining access to donated bodies can be challenging, expensive, and require a range of resources not available at all institutions across the globe. While digital visualizations may address certain aspects of anatomy training, the use of complementary physical artifacts offers the potential to enhance educational outcomes in a way not achievable solely through virtual means. To address this gap, this paper establishes and demonstrates a pipeline for the creation of full-color physical facsimiles of cadaveric anatomy. This is achieved through a combination of photogrammetry, mesh and texture editing, and material jetting. The approach is then demonstrated using two case studies of varying geometric and color complexity, including an arm dissection and combined heart/lung model. Through this method of full-color reproduction, true-to-life specimens for anatomy training can be generated and deployed in education.
9:00 AM
PLA-HA/BBG Composite Scaffolds Fabricated by Digital Light Processing 3D Printing for Cranial Bone RegenerationRegeneration: Engin Gepek1; Fateme Fayyazbakhsh1; Osman Iyibilgin2; Lev Suliandziga1; Ming Leu1; 1Missouri University of Science and Technology; 2Sakarya University
Craniofacial defects (CFD) are among the most common bone defects resulting from trauma, inflammation and infection, congenital deformities, and tumor resections, with bone autograft as the standard of care. Synthetic bone substitutes, i.e., scaffolds, are an emerging solution to address the limited resources and technical challenges associated with autografts. In this study porous scaffolds with different pore sizes (500, 650 and 800 µm) and size gradients are 3D printed using digital light projection (DLP) with slurries prepared from the polylactic acid (PLA) resin blended with various ratios of hydroxyapatite (HA), for purpose of cranial bone regeneration. After 3D printing, the mechanical properties, shape fidelity, biocompatibility, and degradation rates of the scaffolds are measured. From the measured results the effects of pore size, size gradient, and the ratio of HA are analyzed.
9:20 AM
Predicting the Fatigue Life of a Multi-Jet Fusion Fabricated Polyamide 11 Ankle-foot Orthosis: Durability Insights from S-N Curve Analysis: Ryan Blakis1; Mladenko Kajtaz1; 1RMIT University
In this study, we assessed the fatigue performance of HP Multi Jet Fusion (MJF) polyamide 11, specifically targeting its application in 3D-printed ankle-foot orthoses (AFO). We produced an S-N curve to characterize the material's endurance under cyclic flexural stress by performing fully reversed flexural fatigue tests according to ASTM D7774. To test the accuracy of the S-N curve in predicting the fatigue life of the AFOs, we subjected 3D-printed AFOs to fatigue testing that replicated real-world stresses. Our results demonstrated a correlation between the S-N curve predictions and the actual performance of the 3D-printed AFOs, providing crucial insights into the life of HP MJF fabricated orthoses subject to fatigue. This study offers a foundation for further research and development in 3D-printed AFOs, highlighting the importance of fatigue characterisation in ensuring patient safety and device durability.
9:40 AM
Design, 3D Printing and Application of Lattice-based Degradable Metal Implants for Bone Regeneration in Load-bearing Bone Defects: Shantanab Dinda1; Evvie Boas1; Ibrahim Ozbolat1; Timothy Simpson1; 1Pennsylvania State University
Bones naturally self-repair in the case of fracture or minimal bone loss. However, issues such as misalignment, extensive bone loss, and large fracture sites can hamper this process, especially for load-bearing bones below the waist. Existing procedures can correct misalignment; however, more complex cases require highly invasive permanent solutions like rods or plates. A temporary solution that accommodates loading while the bone regenerates may help avoid such permanent solutions. This study discusses the design, simulation, fabrication, and evaluation of a lattice-based degradable metal implant for load-bearing fracture sites, where the implant gradually degrades as the bone is repaired. The goal is to design a degradable implant to meet the load-bearing requirements while minimizing the amount of material. This study discusses experiments performed to evaluate biocompatibility, tissue-metal interface, and mechanical performance. Along with previously performed material characterization and biocompatibility studies, these investigations are essential to developing a functional degradable metal implant.
10:00 AM
Using Trilinear Coordinate Measurements to Inform Prior Models for Minimally-Invasive Material Extrusion Path Planning: Jacob Colwell1; Zyaire Howard1; David Hoelzle1; 1The Ohio State University
Intracorporeal bioprinting, meaning printing inside the body, is an emerging technology at the intersection of Additive Manufacturing, Surgical Robotics, and Tissue Engineering. Intracorporeal Bioprinting may improve outcomes over conventional bioprinting by manufacturing tissue engineering constructs directly in the body, reducing morbidities and decreasing recovery times. In this application, it is difficult to acquire data about a surface because surfaces in the body are deformable. Several methods have been presented previously, but many incorporate scanning methods which may be ineffective inside the body. We propose a method for using data from a CT scan as an initial estimator of the surface, followed by Trilinear Coordinates Measuring to adapt the model to changes in the surface. The method will be evaluated by using a benchtop bioprinter to extrude biomaterial mimics onto predesigned surfaces that exhibit a range of curvatures where the CT scan does not accurately represent the surface.
10:20 AM Break
10:40 AM
Towards the Feasibility Analysis and Additive Manufacturing of a Novel Flexible Pedicle Screw for Spinal Fixation Procedures: Yash Kulkarni; Susheela Sharma1; Jared Allison1; Jordan Amadio2; Maryam Tilton1; Farshid Alambeigi1; 1University of Texas at Austin; 2University of Texas Dell Medical School
In this paper, we explore the feasibility of developing a novel flexible pedicle screw (FPS) for enhanced spinal fixation of osteoporotic vertebrae. Vital for spinal fracture treatment, pedicle screws have been around since the early 20th century and have undergone multiple iterations to enhance internal spinal fixation. However, spinal fixation treatments tend to be problematic for osteoporotic patients due to multiple inopportune variables. The inherent rigid nature of the pedicle screw, along with the forced linear trajectory of the screw path, frequently leads to the placement of these screws in highly osteoporotic regions of the bone. This results in eventual screw slippage and causing neurological and respiratory problems for the patient. To address this problem, we focus on developing a novel FPS that is structurally capable of safely bending to fit curved trajectories drilled by a steerable drilling robot and bypass highly osteoporotic regions of the vertebral body and simulate its morphability capabilities using finite element analysis (FEA). We then additively manufacture the FPS using stainless steel (SS) 316L alloy through direct metal laser sintering (DMLS). Finally, the fabricated FPS is experimentally evaluated for its bending performance and compared with the FEA results for verification. Results demonstrate the feasibility of additive manufacturing of FPS using DMLS approach and agreement of the developed FEA with the experiments.
11:00 AM
Greyscale DLP-Engineered Spatiotemporal Hydrogel Scaffolds: Domenic Cordova1; Maryam Tilton1; 1University of Texas at Austin
Digital Light Processing (DLP) presents a superior alternative to microextrusion in 3D bioprinting, offering high-resolution printing and structural fidelity. In particular, visible light-induced DLP (VL-DLP) enhances cell viability and functionality compared to UV photocrosslinking. This study introduces a novel approach by integrating greyscale VL-DLP with an engineered composite hydrogel formulation to develop spatiotemporal scaffolds aimed to guide cell migration, proliferation, and differentiation fate. We controlled the biophysical properties at each layer by adjusting light intensity to a pixel resolution of 35 µm. We used a photocrosslinkable ink composed of gelatin methacryloyl (GelMA) and polyethylene glycol diacrylate (PEGDA) at a 10% w/w concentration. Employing optical fiber-based interferometry nanoindentation, we have shown that precisely crafted scaffolds were achieved with gradient Young’s moduli varying from 15 to 160 kPa across each layer, demonstrating our technique’s potential for development of tailored therapeutics and more accurate in vitro 3D tissue modeling.
11:20 AM Cancelled
Numerical Modeling of Hydrodynamic Shear in Extrusion 3D Bioprinting: Yousef Bani Ahmad1; Shihab Shakur2; Srikanthan Ramesh2; Iris Rivero1; 1University of Florida; 2Oklahoma State University
In bioprinting, numerical simulations enable detailed observations of parameters unmeasurable in experiments and reduce perturbations from direct measurements, facilitating cost-effective parameterization studies. However, their efficacy hinges on accurately replicating bioprinting conditions. Current models often overlook living cells in bioinks, focusing solely on hydrogel components, leading to inaccurate predictions of cell viability. This study proposes multi-phase computational fluid dynamics (CFD) models to simulate hydrogels and cells' concurrent flow through typical bioprinting nozzles. Using compressible and laminar flow assumptions, we will calculate variables such as shear stresses and pressure by numerically solving governing equations. Additionally, a Lagrangian discrete phase model will predict cell trajectories under various conditions. The model's accuracy will be validated through empirical studies involving printing alginate-based bioinks. This approach aims to yield novel insights for optimizing bioprinting conditions to enhance cell viability and inform the improvement of extrusion dispensing systems.
11:40 AM Cancelled
Development of a Low Inertia Quick Dispenser for Delivery of Heterogeneous, Graded-Biomaterial Using Voice-Coil: Indira Dwivedi1; Bharat Dwivedi1; Rajeev Dwivedi2; 1Eastlake High School; 2STEM and Robotics Academy
3D printing of biomaterial requires dissemination of multiple materials. Ability to modulate the composition of material presents an opportunity to function based customization. Typical multi-material systems are limited by the response time. Additionally, variation of force across the actuation stroke presents inconsistencies in the delivery of material quantity. Motivated by the unique abilities of voice coil, we are developing a high performance and accurate dispensing system. The system is based on voice coil. Actuation pulse profile and subsequent impact is tested. The impact of material viscosity and estimation of error composition is suggested.