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The primary focus of this project is to create a device that will improve the ability to conduct pneumatospinning experiments. This will be used to research an alternative to tissue engineering. The objective is to provide modularity and improve the variability of the experiment parameters. Pneumatospinning involves generating three dimensional fibrous scaffolds from a liquid solution. Pressurized gas is driven through the outer layer of a coaxial needle with polymer solution through the inner layer.
Tissue engineering is synthetically generating type 1 collagen in order to repair tissues within the body [3]. Specifically, tissue engineering is important for repairing meniscal tissue tears through surgery. This surgery may be improved by replacing the torn meniscus with tissue engineered scaffolds. The generated scaffolds must be very porous in order for body fluids and cells to pass through and live there.
Additionally, being able to research the development and structure of these scaffolds is important because the individual scaffold properties such as the fiber diameter, porosity, and structural organization can vary depending on the experimental parameters of pneumatospinning. For example, by changing the solution concentration, needle to ground distance, and collector distance from the needle different types of scaffold structures may be generated [3]. Therefore, this pneumatospinning apparatus will allow for further investigation of ideal scaffold structures by providing a modular experimental platform where each parameter can be controlled.
Figure 1: The final CAD assembly of the pneumatospinning apparatus chamber.
Figure 1a: CAD model of the ramé-hart triaxial needle and custom machined mount.
Figure 1b: CAD model of the Arduino-controlled Syringe Pump purchased.
Figure 1c: CAD model of the collector mesh, brushed DC motor & mount.
Figure 1d: The heating pad that used to warm incoming air and provide humidity control within the chamber.
Modular Experimental Device
Modular Experimental Device
The final design of this project is a modular and automated experimental set up that facilitates research of pneumatospinning. The device contains an air compressor for the outer layer of air in the triaxial needle that shapes the Taylor Cone. This air is passed through a dehumidifier which lowers the system’s overall humidity levels before entering the sealed chamber. The syringe pump is mounted outside the chamber and ejects fluid into the middle layer of the triaxial needle. The triaxial needle allows the compressed air, and liquid solvent to be coaxially joined and ejected as a single stream, forming the Taylor Cone, before evaporating and landing on the collector mount. The rate of the syringe pump is controlled by an Arduino in millimeters per hour. The chamber contains the triaxial needle on a modular mount which can adjust the angle of the needle to the ground. The chamber also contains a modular motor mount which can adjust the height and distance from the needle. The speed of the motor is controlled by an Arduino. Behind the motor mount is an inline duct fan connected by aluminum ducting that acts as an exhaust for the toxic fumes going into the fume hood. The mass flow rate difference between the exhaust fan and the air compressor constantly drives air from the surrounding room into the chamber from the bottom of the door side which is not sealed by silicon gaskets. This air passes over a low profile enclosure heater as it enters the chamber, lowering the relative humidity by the temperature increase before being exhausted out of the chamber.
Another component of the final design is the electrical interface. There is a liquid-crystal display screen (LCD) that shows the motor speed in real time so the user can ensure proper functioning of the device. All of the electrical components are connected by a printed circuit board (PCB) to allow for easier transportation and minimizing the risk of disconnected wires. The automated syringe pump has its own electrical interface that sets the speed at which fluid is perfused and the time duration for the automated process. All the electrical components are stored in a 3D printed box for ease of use to have all controls in one area.
Summary of Performance
Summary of Performance
The design proved successful due to its ability to generate tissue engineering scaffolds. The pneumatospinning apparatus is a functional, modular, and automated device that simplifies the experimental process needed to create tissue fibers by pneumatospinning. With a sealed chamber and humidity control, this device allows for research to occur on any given day despite the humidity levels. This has proven significant improvements in parameter control and efficiency in comparison to the current model. The modularity and ease of fabrication of this device will allow for further modifications and design iterations as needed to continue experimenting with tissue engineering. With the improvements made to pneumatospinning tissue fibers, further research may be developed to design an effective solution to meniscus tears.
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