Microbial Fuel Cell based on Exoelectrogenic Bacteria-

Electrode InterfaceMEMS 2009

26 January 2009

Erika ParraUC Berkeley

Nature’s Solution: Organic Power

100W 850 W ProkaryoteUp to 5 W/mL

15min 42km

Applications: Artificial Metabolism

Honda’s AsimoPortable

MEMSRobotsRemote sensors

2.5 mm

Solar cell

Hollar, Pister (2001)

Mechanism: Scavenging from Metabolism

Enzymes

ATP

H+

e-

O2

H2O

CO2

Electrochemical Fuel cell:• Charge separation• Externalization

MedOx

MedRed

Previous Work: Thylakoid Photo Fuel Cell

Electrodes

V CATHODE

Plant Thylakoids

ANODE

PMSe-

e-e-

e- e- e-

H+H+ H+

H+H+

PMSFe(III)

Fe(II)e-

Problem: Very low efficiency due to diffussion of electron transfer process

Lam, Johnson and Lin, JMEMS, pp. 1243-1250, 2006

IVMn,IIIFeExtracellular Acceptors

O2H14e24H26O 22 Intracellular Acceptors

Microbiology: Exoelectrogenic Bacteria

Cytoplasm Periplasm Extracellular

e-

Organic nanowire

Cytochromes

Geobacter sulfurreducens

NADH

NAD+

MedOx

MedRed

Biofilm: Protein Nanowires

Reguera and Lovley, Nature 435, 1098-1101, 2005

Multiple and connected

5nm x 10m Biofilms < 50m

Device: Fuel Cell

O2

H2O

H+

e-

Anode Cathode

PEM

Bacterialbiofilm

Respiring on electrode

Can we do it? Power Source

Questions?1. Voltage2. Power Density 3. Bacteria Viability /Biofilm

Fabrication: Fuel Cell

Electrode carrying chip

RE

CE

PEM

catholyte

anolyte

Vload

Vref

WE

Reference electrode

Cathode

Anodic chamber

Micro-Electrode

Load

• Vertical 3-electrode• Quasi-ideal system

Fabrication: Anode

• Planar electrode electrical response • Electrodes

– Surface area (1-2 mm2) – Grid geometry

• NW and biofilm

100µm

2µm

Si wafer

Insulating oxide

Gold electrode

Photoresist

-0.2

0

0.2

0.4

0.6

0.8

0 5 10

Time (min)

Vo

c (V

)

Steady state Control

Results 1: Voltage Potential

O2 ≈.8

H2≈-.4

??

Fe(CN)63- ≈.4

0.6V1.2V

O2 ≈.8

??1.0V

Reactant?

• Intrinsic of reaction• Electron energy drop Open Circuit Voltage

Voc ≈ 550-620 mV (vs. ferricyanide)

0.0

0.5

1.0

1.5

0 200 400 600Voltage (mV)

Cu

rren

t (

A)

Results 2: Power Density

16 10 days

0.00

0.05

0.10

0.15

0 0.3 0.6 0.9 1.2 1.5

Current ( A)P

ow

er (

W

)

200mV, 10 days

.1

• 1 mm2 planar electrode• P = 10 µW/cm2

• Full capacity?

Results 3: Bacterial Loading

Au SiO2SiO2

Max. Current

(µA/mm2)

Day 0.1 1 6 10

0.30.6

1.4

?

BiofilmDensity/NW

Metabolic – 10X• Catalyst loading• Biofilm• 3D

Future Work: MEMS for MFCs

Au

Nanowire transport Biofilm connectivityReal-time activityMoving target

ΔHcº (HHV)

Bacteria Device Usable

MJ/L MJ/L % Eff. MJ/L

Acetate in MFC 15.3 1.9 60 8.0

Gasoline 34.2 20 6.8

Hydrogen (liquid) 10.1 60 6.1

PotentialSystem Energy Density

Conclusions…

Biomimetic and Sustainable

Approach to Energy Conversion

Performance (first demonstration)

Voc ≈ 600mV (1 V vs. O2)

Imax ≈ 1.5 µA/mm2

Pmax ≈ 0.1 µW/mm2

Need higher resolution and real-time monitoring

Prof. Lin, Erika Parra, and Ryan YangMechanical Engineering

Prof. Coates and Kelly WrightonPlant and Microbial Biology

Prof. YangChemistry

Team and Collaborators

Supporters

SPS Program

Special Thanks…

IEEE