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Project Background
Project Background
Millions of people around the world suffer from cartilage deterioration in their joints, which can lead to arthritis and chronic joint pain, reducing the ability for smooth joint movement. Current technology for repairing this damage involves highly invasive joint replacements, which can be very expensive and lead to more serious complications for patients in the future.
*An effective, less invasive method for repairing acute defects before they develop into more severe cases would provide relief to individuals suffering from cartilage deficiency, thus improving their quality of life.
Bio-ink Mixture used for Extrusion-based Bioprinting
Introduction to Bioprinting
Introduction to Bioprinting
Bioprinting is the process of assembling cells and biomaterial into a gel-like substance known as bio-ink, which can be extruded from a syringe to create living tissue. Utilizing extrusion technology similar to 3D printing, this process has the potential to be performed in-situ (directly at the surgical site), making it a promising option for tissue engineering and reconstruction.
English Rabbit Test Patient
Healthy Knee Joint (Left) vs. Damaged Joint (Right)
Minor Cartilage Defect
(optimal operational state)
Objective
Objective
The focus of this project, sponsored by the Institute for Biomedical Sciences, is to create a minimally invasive and automated surgical repair of damaged knee cartilage using precision drilling and extrusion-based bioprinting. The device must mill away damaged tissue and bioprint directly into the patient’s knee to fill small defects with bio-ink gel that can integrate with surrounding body cells and form a strong, lasting, and detailed tissue reconstruction. Given the successful proof of concept for bioprinting on rats, the motivation is to progress animal testing to operate safely on rabbits and larger mammals before reaching clinical trials.
UC SAN DIEGO BIO-MILL
Description of Design
Description of Design
An existing CNC machine has been implemented and repurposed for milling tool and syringe extruder 3D bioprinting capabilities. Some crucial key features for this bioprinter include:
Precise, active dual-toolhead indexing for extremely accurate repair
High-rigidity and stability of the print bed even under heavy weights
Large, open frame design and adjustable z-height for different sized test subjects
A digital microscope camera, touch probe, and laser pointer were modified to calibrate the tool indexing to within 0.1 mm accuracy in all directions. Also, a unique, variable bed leveling system was developed for effortless adaptability and stability. 3D printed bed feet of different heights are fitted to the polished aluminum bed with secure magnets and registration slots that are properly constrained and tested to withstand over 90 kg without noticeable deflection. Gantry risers and easily swappable bed feet significantly increase the working space of the machine, with plenty of added z-height for larger test subjects. Patients can be secured into place with a designed fixture that locks into the threaded holes of the aluminum bed. Milling tool and syringe compatibility are achieved through a custom magnetic toolhead, and a pneumatic extrusion system allows for precise extrusion of bio-ink directly into the damaged area.
Summary of Performance Results
Summary of Performance Results
Successful operation on foam material, sawbone, grapes, and finally a rabbit knee
11 minute total procedure from start to finish ✅
Toolhead Indexing Accuracy within 0.1 mm ✅
Precise Milling operation immediately followed by Extrusion Filling of the same 5 mm cavity ✅
Additive and Subtractive G-code implementation for smooth transitions between toolpaths ✅
Repeatable, portable, stable, adaptable ✅
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