P18081: Mechanical Bioreactor
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Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

In the Preliminary Detailed Design Phase, Team MYSCLE focused on designing the cell culture chamber of the device. This included:

Due to delays in securing lab access and supplies, all testing will be continued in the next phase. Once the material properties and chamber design of PDMS have been determined, testing and design of the mechanical strain applicator system can begin.

Feasibility: Simulation

Finite Element Analysis (FEA) was performed in SolidWorks on proposed Membrane Chamber Models. Simulations were performed for three different designs of the hole and peg straining system, a slotted system, a two peg system, and a three peg system. The slotted system extensively stretched the wall of the chamber; and therefore, this design had minimal stretching effects on the actual chamber area. This design was ruled out since the desired stretching response should be focused in the chamber area (since this is where the cells will be growing). The three and two peg designs both have increased stress distributions across the entire membrane; however, it appeared that the three peg design exhibited stress concentrations on the left side of the membrane (side of the membrane in motion). The two peg design produced desired stretching effects in the membrane area, and the stresses are more evenly distributed across the membrane when compared to the three peg design. Fillet dimensions have been modified in an attempt to distribute stresses across the membrane evenly; however, results have been inconclusive and more design options will be explored in the detailed design phase.

NOTE:In the design (and as modeled below), two pegs will remain stationary, while two pegs will cyclically move and stretch the membrane. Concerns for stress build-up lie near the two pegs that will be in motion.

Figure 1: FEA Analysis of Slot Design (Mold Chamber under 2.5N uniaxial load, with 1mm fillet)

Figure 1: FEA Analysis of Slot Design (Mold Chamber under 2.5N uniaxial load, with 1mm fillet)

Figure 2: FEA Analysis of 3 Hole Design (Mold Chamber under 2.5N uniaxial load, with 1mm fillet)

Figure 2: FEA Analysis of 3 Hole Design (Mold Chamber under 2.5N uniaxial load, with 1mm fillet)

Figure 3: FEA Analysis of 2 Hole Design (Mold Chamber under 2.5N uniaxial load, with 1mm fillet)

Figure 3: FEA Analysis of 2 Hole Design (Mold Chamber under 2.5N uniaxial load, with 1mm fillet)

Figure 4: FEA Analysis of 2 Hole Design (Mold Chamber under 5N uniaxial load, with 1mm fillet)

Figure 4: FEA Analysis of 2 Hole Design (Mold Chamber under 5N uniaxial load, with 1mm fillet)

Figure 5: FEA Analysis of 2 Hole Design (Mold Chamber under 5N uniaxial load, with 2mm fillet)

Figure 5: FEA Analysis of 2 Hole Design (Mold Chamber under 5N uniaxial load, with 2mm fillet)

Bill of Material (BOM)

Figure 6: Bill of Material: Phase III outlook (items highlighted in green have been purchased/obtained)

Figure 6: Bill of Material: Phase III outlook (items highlighted in green have been purchased/obtained)

Test Plans

TABLE 1:Test Plan List (click link to view test plan outline)
Test Plan # Engineering Requirement Title Purpose
1 2,3,4 Environmental Conditions To ensure that the incubator is maintaining proper temperature, humidity, and CO2 levels.
2 1,5,6,18 Cell Growth/Viability Monitor pH level with media color indicator. Confirm sterile environment with cell proliferation counts and cell attachment.
3 15, 16 Autoclave Testing Determine if selected materials for mechanical strain applicator can withstand autoclave conditions.
4 3 Material Testing Tensile Testing using ASTM standard D638.
5 5,9,13,14 Ease of Use Assembly/Disassembly, Protocol, Intuitive Software, etc.
6 10,14,19,20 Chamber Design Test Ensure chamber growth surface area is sufficient for cell growth and viewable with a microscope. Chamber height compatible with a microscope.
7 9 Software and Device Motion Testing Verify that software performance is acceptable and it is producing desired outputs.
8 22 Cost Determine whether project development costs are fully funded by allocated MSD funds.
9 23,24 Longevity Testing Determine whether the device will withstand multiple uses (equal to five years with ten uses per year).

Risk Assessment

Previous Risk Assessment was updated to include any risk mitigation or new risks identified throughout the preliminary detailed design phase. Through design development, simulation analysis, and preliminary testing, the risks of stress concentration due to pegs and breakage of parts during assembly have been mitigated from a likelihood of 2 to a likelihood of 1. However, Finite Element Analysis Stimulation performed in SolidWorks has identified the risk of stress concentration in the membrane at the edge of the chamber wall. All updates to the Risk Assessment Table were highlighted in yellow.
Figure 7: Risk Assessment (Preliminary Detailed Design Updates)

Figure 7: Risk Assessment (Preliminary Detailed Design Updates)

Design Review Materials

TEAM MYSCLE'S Design Review Presentation can be found here.

Plans for next phase

Team MYSCLE's plan for Phase IV, the last phase of MSD I, is summarized in the MSD I Phase IV Gantt Chart.

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