Team:Harvard/Dailybook/Week1/Widgetry

=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

=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

=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

=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?