Robots will required to work in dirty, dangerous & dull environments

1. Truly autonomous systems will be required to generate and manage their own energy budget [Holland98, Pfeifer96] • This is true of single robots as well as a group of distributed autonomous robots.

2. Robots will required to work in dirty, dangerous & dull environments • Robots will do things you don’t want to do - in a place you don’t want to be - at a time you don’t want to or cant be there. • Robots will need to generate their energy from the environment.

3. SolarBots

5. Collective Energy Collection

6. Microbial Fuel Cells (MFCs) and Autonomous Robots Chris Melhuish, John Greenman & Ioannis Ieropoulos

7. Fuel cells • An electrochemical transducer which converts chemical energy to electrical energy. • Fuel cells consist of anode (-ve) and cathode (+ve) electrodes. • These are separated by a solid electrolyte and a catalyst is used (anode) to speed up the chemical reactions.

8. MFCs • A bio-electrochemical transducer which converts biochemical energy to electricity • In place of the solid electrolyte there is a proton exchange membrane • The catalyst is the bacterial culture

9. MFC history • Luigi Galvani (18th century) observed electricity in the legs of a frog (animal electricity). • Prof. Potter (1910) introduced the first MFC by using E. coli and platinum. • Cohen (Cambridge, 1931) revived Potter’s MFC after it was illustrated how enzymes oxidise food. • Bennetto (1980s) developed an analytical model for the MFC.

10. Analytical MFC model Proton exchange membrane Anode Cathode

11. MFC categorisation • Generation I (Gen-I) • Synthetic mediator based (Bennetto et al 1980’s) • Generation II (Gen-II) • Natural mediator based (Habermann et al 1991) • Generation III (Gen-III) • Anodophillic – no mediator (Lovley et al 2003) • Generation ? (Gen-?) • Anodophillic(?) – natural mediator(?) (Habermann et al 1991)

12. Gen-I

13. Ecobot I

14. Ecobot I - phototaxis

15. Gen-II

16. Gen-II natural mediator • SO4 found in wastewater • No manual replenishment or recycling necessary • H2S is a natural metabolite of the dominant species D. desulfuricans • H2S is continuously ‘produced’ hence MFC can act as an accumulator • Mixed culture hence wider variety of ‘fuels’ can be utilised

17. Gen-III

18. Gen-III anodophillic mediatorless • G. sulfurreducens forms a monolayer on the electrode surface; utilises acetate • First reported species which forms a biofilm of only a single layer! • Cytochromes which use the electrode surface as the end terminal e- acceptor • Electrode becomes part of the microbe’s natural metabolism • The greater the e- demand, the better the performance

19. Gen-? The ‘aromatic’ sewage sludge

20. Gen-? Sewage sludge • Freely available • Energy from waste • Truly wide variety of ‘fuels’ including food waste • Sludge can be used as both the catalyst and fuel (waste treatment) • Can be trained to act as a sensor • No real threat of contamination

21. VO/C = 1.5V VO/C = 0.8V MFC vs. AA alkaline battery AA alkaline cell AcSeSl MFC fed with chitin • Capacity = 2.8Ah • Capacity = 163mAh • Energy = 4.2Wh • Energy = 37.1mWh • Weight = 25g • Weight = 100g • ED = 604.8 J/g • ED = 1.33 J/g • Cost = £0.30 • Cost = £3.00 BUT MFCs offer continuous energy supply

22. Self-sustainability • All of the aforementioned types of MFC can offer self-sustainability iff: • Open system (continuous flow) mode • Inflow of all the necessary ingredients especially the limiting substrate • Outflow of the waste products including dead cells

23. Self-sustainability • Apart from Gen-I, all the other types of MFC can be used in a continuous mode • Combined with the O2 diffusion cathode, these could be used to power robots • POUT from MFCs is no match to the high energy demand of micro-fluidic pumps

24. EcoBot II • Three kinds of behaviour: Directed locomotion Sensing Radio Transmission • All powered by MFC using raw substrate such as flies

25. EcoBot II running on flies

26. TimeAVE vs. distanceAVE for the 5 runs

27. Temperature transmission

28. EcoBot II energetics • Total number of MFCs: 8 • VO/C = 5V ( 8 x 0.6V) • IDIS = C x dV/dt = 26.23mA • ICH = C x dV/dt = 145.7μA • WCAP = ½ x C x (V)2 = 62.02mJ • WCAPOVERALL = 372.15mJ • DistanceAVE = 70cm • TimeAVE = 3hrs 15mins • Speed AVE = 20cm/h

29. MFC typeCurrent [mA]Power [mW]Energy output [J]Energy input [J](Bomb cal)Efficiency %fly insect852149.7784.558chitin1533488.1222539.2peach601740.30123.732

32. Implications • Need for ‘Pulsed Behaviour’ modes of operation • Impact on the ‘action-selection’ problem – the need to take into account future possibilities by storing energy

33. Future work • Run EcoBot II with O2 cathode MFCs • Integrate ingestion and waste removal systems • Get the flies to the robot • Move to a continuous flow MFC using soft tubing