Design & Development
Design
The design of the fluid pump focused on using a pneumatic actuator and orienting it in such a way that the soft expandable portion would be placed facing the interior of an empty chamber where fluid could fill and having the stiffer base of the pneumatic actuator facing the outside of the chamber, or creating the outside wall of the chamber, giving it structure and constraining the direction that the actuator can inflate so that it inflates inward toward the center of the chamber. The human heart works in a similar way with a soft contractile muscle tissue surrounding a chamber that fills with fluid when the muscle is relaxed and ejects fluid when the muscle is contracted.
Development
The first step was creating a reverse mold to cast the pneumatic actuator. Following the geometry and dimension of the example pneumatic actuator mold, a much larger pneumatic actuator mold was created in Autodesk Fusion 360 that would create a pump approximately the size of the average human heart. The mold was 3D printed from PLA on the Ender 3D printer (Creality Ender-3). A cast of the pneumatic actuator was poured using Ecoflex. The base of the pneumatic actuator was created from placing a piece of paper between Ecoflex in a shallow rectangular mold.
An adapter to allow the syringe to pump air into the five ports was modeled in CAD and 3D printed on the Ender 3D printer.
A CAD of the rigid cylindrical casing was made and 3D printed out of PLA. The casing was filled with fluid and shown to be not water-tight. Silicone sealant had to be applied to the entire internal surface of the casing to address this problem. Five holes were drilled into the casing at the enclosed end. The five actuator tubes were shuttled through the holes assisted by guide strings, and the pneumatic actuator was rolled up and inserted into the casing with the pocket side facing the middle chamber of the casing.
The final step was to attach the inlet and outlet tubes that were connected to one-way valves to the chamber.
