P18081: Mechanical Bioreactor
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Detailed Design

Table of Contents

Team Activities for Detailed Design Phase

During the detailed design phase, the team

Progress Report

Team MYSCLE'S Progress Report can be viewed here.

Design Updates

During this phase a new cell line, 3T3 fibroblasts, was proposed to be used with our cell straining device. After continued testing, design, and research, it was found that the 3T3 cell line proved to be more advantageous for our use when compared to the originally chosen SHOX2 cell line. A Pugh analysis comparing the two cell lines was completed to finalize our decision to change cell lines.
Figure 1: Cell Line Pugh Analysis

Figure 1: Cell Line Pugh Analysis


Strain application mechanisms were researched throughout this phase. The three main approaches were Rack-and-Pinion, Piston, and Adjustable Stroke designs. A Pugh analysis was completed to decide which design would best fit the project's parameters. In the end, the Rack-and-Pinion design appeared to best suit our criteria.
Figure 2: Strain Application Pugh Analysis

Figure 2: Strain Application Pugh Analysis

CAD Models

CELL CHAMBER MOLD:
During this phase, the original mold design was 3D printed and tested. Attempting to mold a PDMS chamber (see Figure 8 for PDMS molded chamber), design flaws were identified and discussed for the second iteration of the mold design. A few of the major problems encountered during the molding process were no visibility of the PDMS solution within the mold and failure to open mold post curing. The mold was redesigned to include viewing "windows" and eliminate the lip on the lid. CAD models for both the original and updated mold designs are found below. Figure 7 illustrates both of the 3D mold prints in a side-by-side comparison.
Figure 3: Original Mold (Top)

Figure 3: Original Mold (Top)

Figure 4: Original Mold (Bottom)

Figure 4: Original Mold (Bottom)

Figure 5: Mold 2.0 (Top)

Figure 5: Mold 2.0 (Top)

Figure 6: Mold 2.0 (Bottom)

Figure 6: Mold 2.0 (Bottom)

Figure 7: 3D Printed Molds- Original Mold (Left) & Updated Mold (Right)

Figure 7: 3D Printed Molds- Original Mold (Left) & Updated Mold (Right)

Figure 8: Molded PDMS (from Original Design)

Figure 8: Molded PDMS (from Original Design)


ACTUATING SYSTEM ASSEMBLY:
The CAD model below illustrates the full assembly of the cell straining device. The device utilizes a hole and peg cell chamber, along with a purchasable actuator that mechanically strains the cell chamber.

Figure 9: Preliminary Actuator Design: Full Assembly

Figure 9: Preliminary Actuator Design: Full Assembly

Bill of Material (BOM)

Figure 10: Bill of Material: Phase IV outlook (items highlighted in green have been ordered)

Figure 10: Bill of Material: Phase IV outlook (items highlighted in green have been ordered)

Test Plan Updates

While planning for MSDII, the need for PDMS Heat Curing Testing and Cellular Response to Strain Testing became evident. Test plans 10 and 11 were created to account for these parameters. Table 1 shows the revised list of Test Plans.

TABLE 1:Updated 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).
10 11 Heat Cure Testing Determine whether different heat cure conditions affect the material properties of PDMS.
11 11 Cellular Response to Strain Determine the effects of different strain % and frequency of strain on the cell culture formation.


During this phase, material testing (Test Plan 4) was completed for 3 different ratios of PDMS (8:1, 10:1, and 12:1). Complications with the Instron machine led to inconclusive results for 8:1 and 12:1 ratios. However, results obtained from 10:1 ratio appear to meet our desired material properties. In addition, literature research has shown that 10:1 ratio appears to be the gold standard used in several laboratories. Summarized results of elastic moduli for 10:1 ratio PDMS are illustrated below in Figure 11.

Figure 11: Elastic Moduli Calculations (10:1 Ratio PDMS)

Figure 11: Elastic Moduli Calculations (10:1 Ratio PDMS)

Risk Assessment

Team MYSCLE was rewarded with a $500 ASTM Project Grant. This mitigated resource risks for the projects budget. The Risk Assessment has been updated to reflect this (highlighted in yellow).
Figure 12: Risk Assessment: Phase IV Updates

Figure 12: Risk Assessment: Phase IV Updates

Design Review Materials

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

Plans for MSD II

During MSD II, the team will build and test the cell culture, strain applicator, and software subsystems. User testing will be completed during the final two phases to ensure that device is appropriate for student use. All design iteration activities will be completed by the Imagine RIT festival near the end of the semester.
Figure 13: MSD II Project Plan before Spring Break

Figure 13: MSD II Project Plan before Spring Break

Figure 14: MSD II Project Plan after Spring Break

Figure 14: MSD II Project Plan after Spring Break


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