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The print head is responsible for moving the cell delivery and cell retraction systems in 3D space. The print head accomplishes this by using three hydraulic actuators that can extend and retract in the z-direction (defined as the axis perpendicular to the printing surface). • Its movement resembles that of a delta printer, so the position of the syringe can be computed by determining the intersection point of three spheres of constant radius. • Water was selected as the hydraulic fluid over oil based on low operating temperatures and low risk of damage in the event of failure. • Magnetic balls and arms are used to connect the pistons to the printing stage, which acts as the mount for the cell delivery and retracting assemblies. • A custom hydraulic cylinder was designed in-house to fit the size limitations imposed by the microscope. 6061 aluminum T6 was selected to make up the body based on its high yield strength and relatively low weight. • M410K pumps were selected based on their ability to exert an excess of the 16.9 kPa needed to move the print head. The pumps are also rated to operate at <3dB, which is critical for laboratory environments. • The print volume was computed to ensure that the delta design was able to print in an entire well of a 96-well-plate (6.94mm x 6.94mm x 11.65mm. The print volume is shown below. The remote systems mount contains all the components that drive the bioprinter. These components are stored in the housing which contains a clear acrylic panel that provides visibility of the fluid levels in the reservoirs. • Quick disconnects are used for all fittings to minimize setup and transport time. These are color-coded to assist the user. • The Smoothieboard and 12V power supply can be accessed via the side panel. • All pumps and motors can be accessed by removing the acrylic panel. • Fans are used to cool the case and maximize cell vitality. • An acrylic door allows for quick access to the print fluid reservoirs. Abstract The Printology 3D bioprinter was designed for the University of Florida Soft Matter Engineering lab with the objective of capturing the group’s passion for product versatility and proclivity for user-friendliness while minimizing cost. The product’s quality was not compromised at the expense of reducing cost. The printer aims to use the same connectors, fasteners, and components throughout to facilitate user repairs and adjustments, unless otherwise necessary. The bioprinter’s cell delivery and retraction operations are performed by two separate mechanisms to avoid cross-contamination of cells. During a literature review, it was found that micropumps and piston actuators work best for deposition and retraction, respectively. Both of these systems were realized in the final design. To prevent cross- contamination at the printing interface, two separate needles were also utilized for the two mechanisms. To ensure that only one needle was in the print medium at any given time, a pneumatic mechanism that induces motion in the z-direction was added to one of the syringes. The motion of the primary print head is achieved using hydraulic cylinders to reduce vibrations caused by motors and other electro-mechanical actuators. The electronics, fluid reservoirs, pumps and motors responsible for the printhead operation and fluid transportation were stored in a remote enclosure. Additional space in the remote mount was also allocated to the Smoothieboard 5X, a power supply, and fans for cooling. The fluid transportation system includes all parts that move cells from the fluid reservoirs in the remote systems mount to the print head • A belt actuator is used for retraction based on its superior performance to micropumps in this area. • A micropump was selected for deposition based on its accuracy and ability to hit low volumetric flowrates. • PVC piping was used throughout based on its sterility and user replaceability. • Off-the-shelf syringes were selected based on availability to the user and decreased production costs. The cell delivery and retraction systems consist of the syringe bodies, needles, and pneumatic actuators that allow for the direct insertion and retraction of cells in a print medium. • Both syringes have a luer-lock connection and have a default 200 µm tip diameter. • Pneumatic actuators give the syringes a stroke of 20 mm. Design Specifications: • 198.4 g • 80 mm x 90 mm x 90 mm when the needles are fully retracted. • Total product cost of $2,579.36 • OTS parts - $2,047.91 • Raw materials - $133.85 • Assembly - $397.60 Printology Group 1: Marilyn Braojos, Nicolas Camejo, Carlos Carrasquillo, Isaac Corcoran, Jose Medina, Lorayne Reyes Pajon
