Sketch Optimization and Problem Solving

Kevin continued to work to optimize the SolidWorks file. This was an important step because many of these parts will be sent off for machining and processing (both at Mount Sinai and the Zahn Center at City College). Issues have arisen in terms of connecting the parts of the bases together as well as motor space requirements. There are some problems with motor power and the group ordered a stronger Bipolar Stepper Motor as a possible fall back, but the size of this new motor is a lot larger than the previous one.

These seemingly minute issues can have large impact on the machining process so these changes are important to finalize early on as to prevent wasting of time/effort/money. Attached is an updated sketch from SolidWorks made by Kevin that demonstrates the bioreactor mechanism of action through a different angle:


Remaining Problems

Today’s lab was spent on working on specific issues we’ve been having:

Mitch, Pete, and Kevin are working on the mathematics involved for the specific measurements for the actuator arm’s placement on the base.


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Grace and Ben are working on configuring the Stepper motor with Arudino


3D Printing of Small Parts Process

Grace has been in contact with Arthur from the Zahn Center at City College who will be helping us 3D print some of the small pieces that connect to the tissue and dish forks. We had our first iteration of parts printed as a test from MakerBot.


It is clear that we did not put enough of a tolerance between the parts as they weren’t able to connect properly. The flimsy material of the MakerBot might not be sufficient for our purposes. We are currently working on a updated iteration.

Machining Process

With the SolidWorks file almost finalized, Pete helped us import the sketch file to CNC machine for initial machining of the base components. We realized that we did not add holes for the base pieces, which had to be updated.Image


Testing limits of sample tissue properties

With our test velcro-tissue samples solidified. Dr. Costa suggested the lab do a simple shear stress test on the samples. For each sample, we manually sheared the tissue with tweezers in a vertical direction to gain a sense of the tissue endurance. What follows is an example:


Tissue Movement

Testing Tissue Properties (Part 2)

After about 48 hours the tissue on the test plates congealed and were ready to be checked. Overall the outcome seemed very promising and most of the tissue seemed to entangle within the velcro! The next step will be to determine which velcro apparatus is the best candidate.

Camera images:

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Microscope images:

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Testing Tissue Properties (Part 1)

As the prototype sketch is nearing completion, we needed a little bit more information about the cardiac tissue properties. For the petri dish/arm complex, we wanted to utilize velco as a means of connecting the tissue to the device. The sketch could only be finalized once we were sure that the tissue could actually adhere to the velcro. Accordingly, we set up some test plates with various velcro apparatuses and grew tissue according to the pre-designed protocol.



Bioreactor sketch updated to SolidWorks

Kevin has taken the preliminary sketches that were made in Google Sketchup and translated them into SolidWorks. The base/actuator arm/dish arms complex was focused on to simulate the movement that will occur in the prototype.

Here is an example of the prototype’s arm movement:


Parts: Actuator arm (blue); dish arms (connected from actuator arm to petri dish); motor (circle in top right)

Here, the motor will push the actuator arm back and fort, which will move the dish arms up away from the static arms. This will ideally cause a shear strain on the cardiac tissue which is located between the dish arm and the static arms on each petri plate.