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Mechano Cell Stretching Device 

Spring 2013 MAE 156B SPONSORED PROJECT - Team 3

Antonio Carreno, Taylor Linkenhelt, Benjamin Robles,

Jordan Smilo, & Anthony Teresi

UNIVERSITY OF CALIFORNIA, SAN DIEGO

SPONSORED BY Valmik Bhargava (Ph.D.)

Overview of Project

Dr. Valmik Bhargava and his fellow researchers at the School of Medicine perform research on how cells, particularly neurons, react when stretched. The current method being used for observing these reactions(under a microscope) involves attaching the cells to a special Petri dish device which has a stretchable membrane along with four buttons along the outer rim. These buttons, when pressed by hand, apply stretching force in the direction of the button (see figures below). While this is an effective way of physically stretching the cell there is no way of determining the input stretch and the process is not repeatable. The proposed membrane stretching device would give the researchers a way to accurately control the stretching of esophageal neurons. Building a membrane stretching device would give the researchers a means to obtain the data needed for their research.

Note: More information about the team's final delivered products can be found in the executive summary, downloadable from the Hi-Res page on the side-bar.

Existing "By-Hand" Device being used to stretch neurons (Left) has now been replaced with our automated cell stretching device (Right)

Mechanics behind how downward linear translation, from pressing on buttons, is converted to horizontal stretch

Project Goals - Spring 2013, Team 3

Functional Requirements:

High Priority:

• 1. Provide controlled bi-axial stretch with given user input (percent stretch) on any axis of neuron orientation.

  2. The neuron of interest must stay in microscope view during stretching.

Second Priority Objectives:

• 1. Mechanism must be able to fit within dimensional constraints of multiple microscopes

  2. Remote device interface and control, with the simplest controls and setup requirements, while integrating with researcher workflow.

Deliverables:

1. Stretch and rotation device

2. Remote interface and Control for the device, to be accessed be sponsor-owned laptop computer

3. Up to 40 appropriately-sized stretchable Petri dishes, and instructions for further fabrication.

4. Documentation (instructions, drawings, etc..)

Project Results in Spring 2013:

Annotated CAD Model of Final Device

In order to satisfy all given requirements, the team undertook efforts in hardware and software. The hardware device is mounted on top of the microscope stage used by the researchers, and is controlled remotely via custom-designed software loaded onto a computer in the researcher's lab. Interaction between the device and the end user is facilitated through a Graphical User Interface program which was developed by the team in MATLAB. This program takes in user inputs (desired percent stretch and desired angel to stretch along) and then sends commands to the appropriate linear actuators to begin stretching the membrane. In order to ensure the object being stretched would not move out of view of the microscope the program utilizes live image feedback and image analysis to regulate motor control. This allows for constant observation of the object while undergoing stretch.

Project Results - Spring 2013, Team 3

Completed Requirements and Deliverables:

High Priority:

• 1.  The device and GUI take in percent stretch and angle from the user, and conduct the stretching process on any angle desired with an accuracy of better than .5% total stretch.

  2. Due to constant video feedback and control, the device is able to keep the neurons within the field of view of the microscope at all times. For stretch under dark conditions, the most recent stretch can be blindly repeated during a fluorescence test.

Second Priority Objectives:

1. Device is remotely and simply controlled to integrate with the user's needs and workflow.

Delivered Items:

• 1.  Membrane Stretching device

  2. Custom MATLAB-based software with GUI and back-end image analysis. Software has been saved as a single executable file, but is modifiable as a MATLAB script to the user's preferences.

  3. Hardware control box, which includes power supply, motor controllers, on/off switch, and cable terminals

  4. Camera for mounting to microscope front port, where it is connected to

  5.  Laptop, with installed custom software.

  6. Custom machined Petri dishes with stretchable silicone membranes, as well as documentation of their fabrication for further production.

  7. Full documentation of the team's progress and instructions

    The following video shows the final device paired with the most up to date revision of the testing code developed in MATLAB, and the Mightex CCD camera to be used on the actual microscope. The video goes through how a typical stretching sequence would take place during an experiment.

Video sequence of events:

1. Image filter parameters adjustment till objects are clearly visible

2. Designation of object to stretch via alignment with crosshairs

3. Axes to stretch along selection (in this case: y axis rotated 30 degrees counter clockwise)

4. Percent stretch to stretch to

5. Controlled stretch via image feedback loop

6. motors reset

7. "Blind" repeat stretch of the controlled stretch

Note: the text in the video is clearest when viewed in HD and full screen.

TAME Cell Stretching Device attached to microscope