IGEM:Harvard/2008/Lab Notebooks/DailyBook/Week1/Widgetry

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Contents

Monday: June 23, 2008

Lab

  • Received ordered parts from McMaster-Carr
  • Drew preliminary designs for MFC

  • Cut polycarbonate tubing
    • 2" Square Tubing:
      • Three 1.5" sections
      • Two 3" sections
    • 3" Round Tubing:
      • Four 2" sections
    • Polycarbonate sheets:
      • Four 3x3" squares
  • Tested 5 minute epoxy:
    • Attached 1.5" (2" Diameter) polycarbonate square tubing to sheet

  • Tested silicon:
    • Attached 1.5" (2" Diameter) polycarbonate square tubing to sheet

  • Tested silver epoxy:
    • Attached titanium wire to graphite sheet

Results

Silicon

  • questionable adhesiveness

Epoxy

  • fairly strong adhesiveness

Silver epoxy

Resistances:

  • Wire : 0.35 Ω / in
  • Graphite: 1 Ω / in
  • Across junction: 5 Ω / in


Purchased

From McMaster-Carr

Qty. Part
20ft High-Temperature Silicone Rubber Tubing Soft, 3/16" ID, 3/8" OD, 3/32" Wall, Blue
20ft High-Temperature Silicone Rubber Tubing Soft, 3/16" ID, 3/8" OD, 3/32" Wall, White
3
(packs of 10)
Aluminum Oxide Cloth Sanding Sheet 280 Grit, 9" X 11"
1 Bright Finish High-Speed Stl Spiral Point Tap 1/4"-28, H3 Pitch Diameter, 2 Flute
2
(packs of 10)
Plain Steel Fully Threaded Stud 1/4"-20 Thread, 6" Length
3
(packs of 25)
Zinc Alloy Wing Flange Nut 1/4"-20 Screw Size, 1" Wing Spread

Tuesday: June 24, 2008

Meeting with Peter Girguis

General Design

  • Three basic designs:
    • Vertical with two chambers stacked
    • Vertical with anode and air cathode below
    • Horizontal (perhaps with incline)
  • Nitrogen/Oxygen bubbling
    • Maybe do in flasks outside of actual fuel cell

Lab

  • Milled holes for injection ports and bolts
  • Assembled prototype for MFC minus anode and membrane

  • Make cathode using alternative wiring design to maximize surface area
  • Made another chamber using epoxy for autoclave test
  • Airtight test by submerging pressurized MFC prototype in water
    • No air bubbles observed

Purchased

From Alfa Aesar

Qty. Part
15x15cm Nafion® membrane, 0.180mm thick
10x10cm Carbon felt, 6.35mm (0.25in) thick, 99.0%

Wednesday: June 25, 2008

Lab

  • Autoclaved epoxy chamber
    • Results:
  • Laminated nafion membrane
  • Made two black silicone chambers
  • Tested MFC by bubbling air into anode chamber to test gas in/out ports
    • Result successful.
  • Wrapped carbon felt with titanium wire without epoxy
    • Resistance:
      • Across junction: 2.5 Ω
      • Felt: 1.5 Ω

Received from Peter Girguis:

  • Decade resistance box
  • Carbon fiber cloth


Purchased

From McMaster-Carr

Qty. Part
1
(packs of 10)
Inline Minature Air Regulator 1/4" Female Inlet, 1/4" Male Outlet, 5 Max SCFM
1
(packs of 10)
Brass Barbed Hose Fitting Barb X Male Pipe for 3/16" Hose ID, 1/4" Pipe
1
(packs of 10)
Brass Barbed Hose Fitting Barb X Female Pipe for 3/16" Hose ID, 1/4" Pipe
6 Polycarbonate Sheet 6" x 6" Sample, 1/4" Thick, Clear
2 Ft. Polycarbonate Square Tube 2" Square Tube
25 Ft. High-Temperature Silicone Rubber Tubing Soft, 3/32" ID, 7/32" OD, 1/16" Wall, Blue
25 Ft. High-Temperature Silicone Rubber Tubing Soft, 3/32" ID, 7/32" OD, 1/16" Wall, White

Thursday: June 26, 2008

Lab

  • finished building MFC
    • added nafion membrane
    • added carbon felt anode

  • membrane did not pass water-tight test
    • silicon sheet started bulging
    • nafion membrane started warping

Warped membrane

Normal membrane

  • new MFC:
    • design:
      • anode chamber
      • outer “ring”
      • polycarbonate with 15/36” hole
      • smaller ring
      • membrane
      • smaller ring
      • polycarbonate with 15/36” hole
      • outer “ring”
      • cathode chamber

  • water tight test:
    • passed water tight test
    • membrane still warps
  • made 1L of LML medium (for anaerobic Shewie growth) ( see recipe here)
    • pH was 3.5 initially
    • added NaOH until pH at 6.99
    • autoclaved

Friday: June 27, 2008

Lab

  • Finished building air cathode MFC, minus injection ports

  • Autoclaved LML

Keithley test

  • Connected simple battery-resistor circuit to both 2700 alone and with 7700 switching module
    • Used 8.78 V source of 4M ohm resistance with 1% accuracy
      • Calculated current = 2.19 microamps
      • Measured current (from 2700) = 2.5 microamps
      • Measured current (from 7700) = 2.8 microamps

MFC test




1k ohms resistance

  • Bubbled nitrogen and oxygen into anode/cathode chambers.
  • 60mL LML medium and 15mL distilled water in anode chamber
  • 40mL of LML and 35mL distilled water in cathode chamber
  • Current began at around 21 microamperes, dropped fairly consistently before plateauing around 10 microamps after 50 minutes
  • Added small amounts of lactate, HEPE buffer, yeast extract, peptone in attempt to cancel out the current
    • saw sudden rise in current, but then decreased again.
    • no notable difference thereafter.

Switched to 10k resistance

  • dropped to about 4 microamps
  • very very very slow increase (about 4.1-4.3 microamps in 10 minutes)

Added shewie

  • initial increase to about 5.25 microamps
  • slow and steady increase to about 6.7 microamps

Switched back to 1k resistance

  • shot up to about 21 microamps
  • decreased to about 13.5 microamps after 10 minutes


Questions to answer

  1. What temperature were the fuel cells kept at? Do they need to be incubated at 30ºC?
  2. What type of shewie is ideal for anaerobic current production? How long should they have grown in liquid culture?
  3. What concentration of shewie should be added per 50 mL of medium? OD?
  4. How much current should be produced over 2 minute increments? Current production over time pattern.
  5. How much resistance should we be using?
  6. What should the voltage difference be? 6 volts?
  7. What is the best medium? Can we get away with our LML medium, or will we need to make the....extensive recipe?
  8. Why is there current production without shewie? Distilled water test?
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