Contribution

Summary

Reproducible and fully 3D printable Glue Gun for Caddisfly silk

The Caddisfly silk is a unique material that can open a variety of opportunities for the medical field. Special properties of the Caddisfly silk will allow for the creation of translational, biocompatible and, most importantly, reproducible gastriarchal patches. However, for proper usage of this material, there is a need for a tool that will utilize all of the special abilities of Caddisfly silk and serve as a convenient and fast applicator for medical professionals. We have created a glue gun that mimics the tensors in the Caddisfly glands, allowing for protein unfolding, solidifying the strand and allowing for convenient application.

Glue gun measurement specifications

Even though there is limited research that has been conducted on Caddisflies, there is information on their biological structure. The protein solution travels through the posterior gland, anterior gland, and then comes in contact with water, thus solidifying. There are two channels which are both rows of such glands, that mix together at the end to create a strand. The measurements are as follows: posterior glad inlet: 50 um, entrance into the anterior gland: 20 um, outlet: 2 um. The tensors resulting from such a drastic narrowing allows for the protein to unfold and create the silk. However, due to the limitations of most 3D printers on the size and resolution of the parts that they are able to print, and with a goal to make this device accessible and reproducible, the device has been scaled by a factor of 25, to allow for proper printing. However, the same measurement proportions have been preserved, and flow studies have been conducted to ensure that the forces are conserved and suitable for protein unfolding. The flow velocities have been modelled via COMSOL, using simulation for laminar flow, with kinetic viscosity of the fluid as 0.45P*s.

Gland flow studies:

Glue gun gland flow studies:

Glue Gun parts

The glue gun parts are as follows: two tubes with two narrowings, which model both glands of a Caddisfly and have the protein solution flowing through. A tube also starts from the bottom of the handle and moves to the ‘glands’. All of the sharp corners that are trespassed by fluid have been rounded to prevent creation of turbulent flow. The bottom opening is created for an attachment of the air compressor, which will serve as the main driving force to push the solution through the glands, the holes on the side are for the injection of the solution for each of the glands. The nozzle at the front of the gun contains water, which allows it to pass the formed strand through the liquid and solidify it, similar to the operations of Caddisfly.

All of the glue gun parts are 3D printable, making it low cost and easily producible. We used the X printer in combination with the printing software FormLabs. The only part that needs to be outsourced is the air compressor, which does not need to be of high efficiency since the mechanics of the gun create internal pressure. The holes could be closed with PDMS after loading of the gun, to prevent any substance from spilling out. The handle and the loading cartridge of the gun allow for convenient loading and application of the Caddisilk. All of the connections on the gun were made no smaller than 50 microns, in order to avoid any issues with printability of the device.

Schematic of printed parts and gun

In order to test the gun, we printed the design as a part in .STL format on XX 3D printer. The printing was successful and there were no issues with the perfusability of the channels.

Lab bench scale low-cost bioreactor with measurable factors

In order to create a reproducible and suitable space for the growth of microorganisms in a controlled environment, we designed a low-cost bioreactor that allows us to measure the temperature and the pH of the cellular contents inside. The Caddisfly silk synthesis in vitro is a challenging and lengthy process, and thus we needed a device that would enable sustainable protein synthesis. The main factors of consideration in this design were the possibility of measurement of the influencing factors such as the environment temperature and the pH, since they can heavily influence the synthesis processes. The reactor is designed to be bench-grade and accessible for manufacturing, thus some of the parts of the bioreactor can be 3D printed, reducing the cost of production even more.

3D Printed Mockup of Silk Net

This mockup of our product was generated in solidworks by extruding a cylinder along the path of a sine wave and adding multiple cylinders together to represent the natural variation in organic nets. The grey exterior represents the caddisfly silk adhesive that secures the green silkworm silk interior. While the exact design is not finalised, this was used for visualization and was an important tool in our communication and outreach efforts, and provided a tangible product to aid presentations and pitches.

Design of the bioreactor

As a chamber, we decided to use a large stainless steel pot, which has a higher biocompatibility than other metals. The temperature can be controlled via a heating strip, which is glued on top of the pot, on which the stainless steel allows transfer of heat inside of the solution. Even placement of the heating strip guarantees even distribution of heat. Furthermore, there is a stirrer that is attached onto an external clamp. The stirrer helps ensure a consistent environment with similar temperature and pH all throughout the liquid solution. There is also a temperature sensor probe and pH sensor circuit board which connects to the pot. The pot can be covered with its own cover and the clamp can be mounted on top of this assembly. In the design, we have also drilled holes for convenience. All of the parts were found online for a small price.

The bioreactor parts such as the pot, the holder and the stirrer can be 3D printed and autoclaved, if the manufacturer so desires. This further reduces the cost and allows to keep sterile conditions.

Bioreactor Assembly

In order to assemble the reactor, we would first drill holes in the pot with the dimensions for the pH sensor and temperature probe, and insert the corresponding devices. Then, we would attach the heat strip to the relay control and a power strip for convenience, and glue the strip on top of the pot, measuring the distance between each wrap of the strip to ensure even distribution. Afterwards, we would drill a hole in the lid for the stirrer and insert it through the lid. Sue to the thick edges of the pot, we would be able to clamp the stirrer holder and insert the stirrer into the lid.