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.

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

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.

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.

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:

Kevin did a great job incorporating the Google Sketch-up schematic into Solidworks with working movement simulation!

(Please click on the picture if the gif does not load)

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:

Microscope images:

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.

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.

With a (somewhat) complete model sketched up, the group has a discussion on the specific parts needed. As the deadline is approaching, we needed to:
a) select which specific materials we need for each part
b) the type of material we need for each part
c) what vendors to buy from

The group decided on this parts list:
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…and the order was placed!