Team:Queens Canada/CAD-Modelling-Iterations
CAD Modelling
Overview
Often, in any engineering project, multiple iterations are needed when designing a model. Critical analysis is utilized to improve each solution. While designing the casing for our QGEM prototype, our process saw five iterations. Even after 3D printing our final prototype, the team believes that this design can be improved by utilizing renewable materials, decreasing the overall size of the device, and completing and testing the device as a whole.
Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5
Iteration 1
Our device was split into two components: the lateral flow immunoassay holder (LFIA) and the sample extraction device. This first iteration focused on the casing for the LFIA. The idea was to make it a renewable test with five uses, as the user would be able to remove the upper components to switch out LFIA strips for each test. The casing contains windows to allow the user to see the test results and apply the solution to the sample pad.
The following complications were encountered:
- How to handle the strips to avoid contamination and the disruption of the test
- How to decrease the number of pieces
- How the pieces will hold together
- How the sample will be applied to the pad i.e., missing the extraction component
Iteration 2
The next iteration built upon the previous design, reducing the number of pieces to two and considering how the pieces will stay/operate together. The top casing was designed to slide on and off the bottom casing to allow the new strips to be easily accessible and stay together when in use.
This design still didn’t address the following problems:
- How to handle the strips to avoid contamination and the disruption of the test
- How the sample will be applied to the pad i.e the sample extraction component
Iteration 3
The next iteration focused on how to avoid strip contamination and making the solution more user-friendly. To avoid contamination, "shelves" were designed to separately hold all five test strips. This also allows the users to easily interchange each strip.
This design still didn’t address the following problems:
- How the sample would be extracted from the tick
- How the sample would be dissolved safely in an aqueous solution and applied to the strip
- If it would be possible for the extraction component and the assay to be on one device instead of two separate devices
Iteration 4
The fourth iteration aimed to design a single device that combined the steps of killing the tick, removing the midguts, dissolving them in an aqueous buffer solution, and applying this solution to the lateral flow assay. The primary idea to extract a sample from the tick was to crush the bug using a pestle over a mesh that would allow the innards to drain into the lysis solution in the lower compartment. From there, the proteins could be lysed and dissolved in the aqueous buffer which once done, could be applied to the sample pad through the use of a funnel. This test aimed to be reusable, with both the strip and lysis buffer cartridge able to be replaced by the user.
While this iteration was able to address a lot of the previous issues, there were still concerns and adjustments that surface that required a fifth design. The following are the concerns and adjustments that were required:
- How to avoid leaking in the assay
- How to easily replace the cartridge and sample pad
- How to adequately squish the bug and puncture the exoskeleton
- If the current extraction method would be able to contain enough solution/space to apply enough force and contain enough solution
- How to apply the solution continuously in small amounts
- How to make it safe for the user
- The mobility of the device; how would the user be able to easily transport the device without fear of losing any components or chemicals leaking in the pack
Iteration 5
The fifth and final iteration of the device was able to address all the previously listed concerns and build upon new elements. This prototype was ready to be printed and field-tested.
Description of Physical Device
The casing and extraction are designed to allow the cartridges and strips to be easily replaced by the user while minimizing leaking concerns. Within the extraction component (the yellow piece), there are three cylindrical chambers. The first compartment is used to puncture and extract the tick innards. This is done through the usage of stainless steel micro-spikes embedded onto the bottom of the pestle, which has been proven to be able to puncture the hard exoskeleton of the ticks. The embedded pestle will be able to apply enough pressure to force the innards out of the punctured holes in the tick’s exoskeleton.
Once the tick is sufficiently dissembled, the syringe preloaded with lysis buffer solution is able to add the solution to the chamber containing the tick remains. The syringe is designed to hold enough solutions that can easily be loaded from a provided cartridge. Here, the lysis is able to break apart the target bacteria and dissolve them into a solution. This is required for two reasons: firstly, the tick sample is small and dense in nature. To dissolve it is necessary to ensure proper flow. Secondly, the bacteria as a whole is too long to flow through the pores of the LFIA. As a result, a lysis reagent is needed to break it up into smaller quantities.
Once sufficient time has passed, a slim tube can be screwed onto the syringe to help extract the solution from the chamber where it can be transferred and applied in the remaining chamber. The syringe is inserted into the chamber which feeds directly onto the sample pad of the LFIA. The syringe is able to provide control to the applied liquid and allow the user to monitor the rate and quantity of solution that is applied. The chamber it is applied through minimizes the risk of the lysis buffer spilling or leaking.
Materials
Every element with the exception of the LFIA, stainless steel pestle, and rubber tip for the syringe will be comprised of plastic. For the purpose of the device testing, the pestle will be printed in plastic and without the microspikes due to the detail limitations of the printer. The rubber tip for the syringe will also not be printed as that material is unable to be printed.
Storage Casing
To store the additional strips and cartridges, as well as the device as a whole, a case is required. The case is able to keep everything compact and organized and greatly limit the risk of breakage or leaks. It is easily stored in a backpack, with no worry of breakage or issues when jostled. It is also able to be hooked onto the outside of a bag through the use of a key ring. The following is a schematic of the housing for the device:
Design Considerations
When designing a case that would be durable, portable, and compact, various factors were considered and incorporated. These include:
- Ensuring all components remain immobile while within the device. This was addressed by adding caps and compartments for all the components. This greatly reduces the risk of spillage or damage during travel
- Easy portability. The case was designed to be as compact as possible to make it easier to pack. To help, a clipping hook was added to the top to allow the case to be clipped onto a backpack or another type of bag
- Easy accessibility and usage. The casing was designed so it is one complete piece and opens using a hinge and stays closed using a clip
- Marketing. To ensure our brand name spreads, ‘SUBLyme’ was etched onto the cover of the casing
- Materials. Our casing will be made of plastic and therefore is easy to transport. The case is water-resistant and durable
Further iterations could work to incorporate a seal to make the casing completely waterproof as well as working to decrease the number of components such as caps.