Engineering Success:

Throughout the course of our project, there were several design changes that came as a result of the Design – Build – Test – Learn cycle. From fabricating several microfluidic chips with different input/channel sizes to 3D printing multiple iterations of our filtration component, we definitely learned a lot from our multiple design changes. We kept note of each change, because just as we learned from the shortcomings of our earlier designs, future iGEM members might benefit from seeing what worked and what didn’t.

Filtration System - 3D printed prototypes:

Our liquid filtration system was very important for the later components of the testing process because of the sensitivity of the microfluidic chips. With such small channels, even microfibers could clog the system. We solved this problem by designing a multi-stage filtration system. Our multiple design changes came from needing a watertight system (something our 3D printed parts couldn’t provide) and ease of access to the user (allowing for the removal and replacement of filter paper for continued product usage). We updated our CAD files throughout the process and also 3D printed a few iterations to get a better understanding of how they would fit into our system. Below are some of the designs ranging from the initial brainstorming stages to our final design concept.

Figure 1.A:
Filtration Tank
Filtration for large debris occurs in the middle of the two tank system
Figure 1.B:
Filtration Device
Slanted Design would provide issues when going to machine final design
Figure 1.C:
Filtration Device V2
Incisions for seamless tank insertion
Figure 1.D
Filtration Device V2.1
Circular Filter for compatibility with easily accessible filter papers
Figure 1.E
Filtration Device V2.2
Two 3D printed iterations of different thicknesses
Figure 1.F
Filtration Device V2.5
Sliding Mechanism to provide access to system from side panel
Figure 1.G:
Filtration Device V3
Sliding mechanism to provide access to system from system side panel
Figure 1.H
Filter V3.5
Incisions for sensors that run from top to bottom of tank

Figure 2: Comparing the different filter designs

Final Multi-Stage Filtration System:

It was at this point we realized that using one tank for filtration and regulation of liquid parameters was unideal. In design V3, you can see that the sensors need to pass through the filtration piece (due to length of sensors). This in turn created waterproofing issues. Because of our project’s heavy reliance on electronics like microcontrollers and Fluigent pressure pumps, it was essential for us to prevent even the slightest of leaking liquid. We turned to a new system that incorporated 3 tanks to solve this issue. The diagram below shows our final system.

This final design incorporates both a horizontal and vertical filtering process. In the initial filtration system, the centerpiece filters for large debris like rocks and pebbles. The liquid is then sent to the simulation tank where sensors and side reservoirs (attached above the simulation tank) allow for sensing and regulation. Because the reservoir liquids have not been filtered yet, the final mixed solution is passed to the secondary filtration and sampling tanks where small amounts of solution are filtered using a sliding mechanism. It was because of our multiple iterations during the prototyping process that we were able to utilize multiple filters for a more comprehensive filtration system. Below you can find the engineering design process we went through; what started with one design resulted in various iterations all from which we learned a lot.

Figure 3: Engineering Design Process

Multifluid Input Design:

To sense and regulate different liquid parameters like pH and salinity, we needed access to small water reservoirs of various solutions (water with high and low pH for example). The issues occurred when trying to determine a way to get precise solutions out of reservoirs into our regulation tank. We needed to be able to move exact amounts of liquid. Our first design had reservoirs directly above the regulation tank; the idea was to use motorized valves to open and close output from the reservoirs. But from testing the reservoirs themselves, it was immediately clear that excess solution would be mixed into the tank due to gravitational forces. From researching and testing different water pumps, we came across peristaltic pumps that allowed for pumping water at fixed flow rates. We no longer needed gravitational forces to move our water.Our final design incorporates reservoirs attached to the sides of the regulation tank and peristaltic pumps moving the liquids between them.

Figure 4.A:
Multifluid Input V1
Initial multifluid input design. Holes on bottom relied on gravity for dispensing liquid solutions
Figure 4.B
Multifluid Input V1
Initial multifluid input design. Holes on bottom relied on gravity for dispensing liquid solutions
Figure 4.C
Multifluid Input V2
Changed design to incormorate peristaltic pumps (controllable flow rates). Simpler design (geometrically easier to assemble)