156B Week 7 Progress

MAE 156B Project Update

Week 7: 05/10/15 - 5/16/15

Team 8:

Nerve Gripping

1. OVERVIEW AND PROJECT STATUS
  1. Tested Prototypes
  2. Made Improvements to Prototypes
  3. Began Compression Testing on Actual Nerve
2. LATEST ACCOMPLISHMENTS

- 1. Contacted other Machine Shops with Micromills
    1. Kenneth Duff - SIOMS
      1. Parts too tiny for fabrication
  2. Results from Initial Prototype Testing

- - 1. Clamp works well, but difficult to tighten
      1. Found the force it takes to make the nerve slip on the clamp
    2. Microbarb layer worse than default surface roughness

- - - 1. Decrease density, but increase overall height

- - 1. Sutures had difficulty staying in place in composite wrap

- - - 1. Guidelines etched alongside of male component to secure sutures during compression.

- 1. Prototype Revisions

- - 1. Microbarbs
      1. Increased overall height and width, kept piercing head same
      2. Designed directional barb prototype
    2. Clamp

- - - 1. Altered fastening method

- - 1. Wrap

- - - 1. Made new mold
      2. Filament Change (Sutures -> Wire)
        Silver plated copper wire
      3. Size constraint proving to be daunting.

- - - - One last iteration then plausible scrap of design
        Use of improved 3D Mold
        Considering mesh iff readily available.

- - - 1. Fabrication of through-holes for sutures unreliable

- - 1. Strap Down Design

- - - 1. Increased size
      2. Changed from half-cylinder clamp to ¼ cylinder clamp
      3. Changed wrapping method and material
        ePTFE and slip knot
      4. Sending prints to Chris

- 1. Located Outside 3D Printers

- - 1. 16 micron resolution

1. GOALS FOR NEXT WEEK

- 1. Prepare Hardware Demonstration
    1. Setup backbone system and movable wall jig
  2. Establish Criteria for Head-to-Head Comparison
  3. Complete Compression Testing Data and Find Relationship Between PDMS and Live Nerve Results
  4. Complete Final Revisions for Prototypes for Head-to-Head Testing

1. SPONSOR COMMENTS

- 1. Clamp Design with Only One Screw
    1. Attach loose slot on other end to prevent rotation
    2. One screw would reduce overall size
  2. Reduce Overall Size of All Prototypes

- - 1. Ag-Cu wire too thick, making unfeasible design

- 1. Try using ePTFE for strap-down

1. INSTRUCTOR COMMENTS

- 1. Proof of Concept Presentation Comments
    1. Prototype barbs to curved part
      1. For next revision, print barbs on channel of clamp
    2. Angled barbs

- - - 1. Printed and tested ested directional barbs

- 1. 1. Add jam cleat to strap down design so no need for a knot
    2. Importance of ensuring even compression on nerve through revised clamp design (with hinge)

1. CURRENT PROJECT RISKS

- 1. Need to Find Biocompatible High Friction Materials
  2. Methods to Bond Gripping Mechanism to Stainless-Steel Backbone
  3. Consider Size and Feasibility for Surgeon

1. NEEDED RESOURCES AND INFORMATION

- 1. Micro-machining Information
    1. Need to find resources on how to machine on our small scale
  2. Accessibility of proposed materials

1. UPCOMING MILESTONES

- 1. 2nd Draft of Report (May 22nd)
  2. 2nd Draft of Webpage (May 22nd)
  3. Head-to-Head Testing (May 25th)

1. BUDGET UPDATE

- 1. $958.87 Parts Budget Remaining ($1000 Starting Budget)
    1. 3D Printed Parts
      1. $100.00 spent for UHD 3D Printer ($100 provided)
        Rate: $0.30 for model material, $0.60 for support material (all per gram)
        Need to verify with Chris on latest printed part
      2. $9.72 spent for lower-res 3D Printer ($100 provided)

- - - - Rate: $5.20 per cubic inch of material combined

- 1. 1. Supplies

- - - 1. $5 spent for presentation printing ($401.33 provided by class)
      2. $ 1.14 spent for the screws and bolts
      3. ~$2.50 spent for clay material for fluid stop
      4. $27.49 spent on tap and tap handle

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