Microfabricated Photosynthetic Fuel Cells Powered By Photosynthetic Bacteria

Microfabricated Photosynthetic Fuel Cells Powered By Photosynthetic Bacteria Powered By Sub. Cellular Photosystems Kien B. Lam Professor Liwei Lin 09 MArch 2003 BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents.

Motivation: Power For… Bionic Cockroaches and Rats Roboroach (I. Shimoyama, Tokyo Univ, 2001) Ratbot (S. Talwar, SUNY, Nature, 2002) Molecular Motors Kinesin motion driven by ATP (R. Vale, UCSF, Science, 2000) Bacteria flagella driven by proton gradient (Centers for Disease Control and Prevention) Silicon robot (S. Hollar, 2003) ATP Synthase powered by trans-membrane proton gradient (Oster, UCB, Nature, 1998) BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents.

Energy Sources Inside a Plant Cell Metabolic processes of The Cycle of Life take place inside cell. Photosynthesis generates NADPH and ATP in chloroplasts Aerobic respiration uses NAD(P)H to generate ATP in mitochondria Electrons (NADPH & NADH) available inside cell A representative plant cell Transport electrons from inside cell to outside using “redox mediator” (PMS) BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents. Voet & Voet, Biochemistry, 1995

Photosynthetic Electrical Conversion V ANODE e- Photosynthetic Bacteria Glucose O 2 H 2 O CO 2 Fe(III) PMS Photosynthesis NADP+ H+ e. Electrodes NADP+ e- CATHODE PMS Fe(II) e- H+ H+ Proton Exchange Membrane (PEM) BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents. e-

Respiration Electrical Conversion V ANODE e- Photosynthetic Bacteria CATHODE e. Electrodes H 2 O CO 2 Glucose Respiration NAD+ e- H+ Fe(III) PMS NAD+ PMS Fe(II) e- H+ H+ Proton Exchange Membrane (PEM) BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents. e-

Design and Assembly Fluid Ports Glass Cover Anode Nafion PEM Cr/Au Electrodes Cathode Glass Cover BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents.

Microfabrication (a) Deposit (LPCVD) and pattern low-stress nitride. (b) KOH etch 350 mm-deep chamber. Silicon substrate Reaction chamber Cr/Au electrode Glass cover (c) Strip nitride, thermally evaporate 2500 Å thick Cr/Au electrode, and cap chamber w/ glass cover. Nafion PEM Anode (d) Sandwich PEM between anode and cathode half-cells. Cathode BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents.

Open-Circuit Voltage in Light 3 Typical Trials Anode Cathode Cyanobacteria (Anabaena) Oxidant: potassium ferricyanide 20 m. M Electron mediator: PMS 10 m. M Sodium phosphate buffer 100 m. M (p. H 7) Growth medium (no glucose) BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents. Lam et. al, MEMS 2003

Open-Circuit Voltage in Dark 2 Typical Trials BSAC © 2004 Spring IAB. Confidential Information.

Closed-Circuit Current in Dark & Light R = 10 W In Light In Dark Peak Power Light: 2 m. A/cm 2 @ 20 m. V P = 40 p. W/cm 2 Dark: 1. 5 m. A/cm 2 @ 15 m. V P = 23 p. W/cm 2 BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents.

Chloroplasts, Thylakoids, Photosystems Plant cell Chloroplast Thylakoid ATP Synthase BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents. Nelson & Cox, 2000

Thylakoid Photo-electrical Conversion V ANODE Plant Thylakoids e- e- e- H+ H+ H+ PMS H+ e. Electrodes Fe(III) PMS e- CATHODE e- Fe(II) e- H+ Proton Exchange Membrane (PEM) NADPH NADP++H++2 e 3 -+2 e- 2 Fe(CN) 42 Fe(CN) BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission 6 6 2 PMSre+2 e- 2 PMSrefrom UC Regents.

Design and Assembly Flow Port Cr/Au Electrode Surfaces Anodically bonded Si. Pyrex Nafion PEM Bioreaction chambers Micro syringe needles glued to flow ports Double-sided tape bonds half -cells to Nafion Au wires soldered to Cr/Au BSAC © 2004 Spring IAB. Confidential electrode pads Information. Not to be made public without permission from UC Regents.

Microfabrication BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without

Experimental Setup Anode Thylakoids isolated from baby spinach, 2. 4 mg Chlorophyll/m. L Thylakoids suspended in 400 m. M sucrose, 20 m. M Tricine (p. H 8. 0), 10 m. M Na. Cl Thylakoids diluted into 50 m. M Tricine, 50 m. M Na. Cl, 4 m. M Mg. Cl 4 to 240 mg Chlorophyll/m. L Redox mediator: PMS 300 m. M Cathode Oxidant: potassium ferricyanide 20 m. M Deionized H 2 O Anode & Cathode BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission Flow: 0. 1 m. L/min from UC Regents.

Open-Circuit Voltage: Dark & Light BSAC © 2004 Spring IAB. Confidential Information. Not to

OCV: Variation with Light Intensity Flow on Half-Intensity Illumination Dark Direct Illumination BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents.

OCV: Interaction of Flow & Light BSAC © 2004 Spring IAB. Confidential Information. Not

Close-Circuit Current: Dark & Light R= 1 k. W BSAC © 2004 Spring IAB.

Voltage & Power v. Current Density BSAC © 2004 Spring IAB. Confidential Information. Not

Summary o Motivation for m. PFCs o Si robots, roboroach, ratbot o Molecular motors o u. PFC by photosynthetic bacteria o Live Anabaena culture o Anode|pem|cathode o OCV 450 m. V, 2 m. A/cm 2 @ 20 m. V o u. PFC by sub-cellular photosystems o Isolate spinach thylakoids o Anode|pem|cathode w/flow o OCV 470 m. V, 1. 1 m. A/cm 2 @ 5. 5 m. V BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents.

Future Directions o Thylakoid m. PFC: Improve efficiency! o Diffusion & transport o Increase [Thylakoid] & [PMS] o Immobilize thylakoids o Alternatives to PMS o Increase electrode area o O 2 oxidation: Bubble N 2 o PEM spin-casting or dip-coating o Fit m. PFC to fuel cell model o u. PFC 3: Bio-reforming H 2 fuel cell o Induce H 2 production from algae o Redesign Anode|pem|cathode o u. PFC-powered molecular motor BSAC © 2004 Spring IAB. Confidential Information. Not to be made public without permission from UC Regents.