Wednesday, 4 April 2012

Virus-drive batteries

Bored with GM food and Dolly? Check out what GM virus can do for us!

Fabricating Genetically Engineered High-Power Lithium-Ion Batteries Using Multiple Virus Genes

Fig.1 A virus-drive battery 

M13?

It is a harmless virus (to humans) that has been well understood in MIT’s laboratory. As viral DNA is pretty simple, previous genetic engineering research on have found that M13 can interact with different materials and its protein coat can been modified to grow desirable materials. This feature has profound importance in boosting the lithium ion batteries’ performance.

Development of virus batteries

According to Trafton(2009), some previous studies have focused on anode and virus that can coat gold and cobalt oxide on themselves was produced. To further improve the batteries, scientists then aimed to improve the cathode. One of the obstacles was that most potential materials are insulating, but in this article MIT has discovered the method to increase the conductivity inside the cathode.

In the past, MIT has used M13 to grow nanowires. When M13 chooses a bacterium to host and undergoes replication (Johnson 2006), therefore nanowires can be manufactured easily. Apart from nanowires, carbon nanotubes (CNTs) are also components in batteries (see fig.2). A single-walled CNT is made up of graphene sheet rolled into a cylinder (Wang et al 2003) which enhance conductivity of electrodes. However the reaction rate is often slowed down by the aggregation of CNTs, as there are fewer nanotubes in contact with the active ingredients.



Fig.2 A carbon nanotube 

The 'two-gene system'

Recently another virus has been produced. Originated from M13, E4 is a multifunctional virus. One part of the virus can grow nanowires like M13 while another part was modified to be able to grip a carbon nanotube and control its arrangement, therefore less aggregation will occur. Researchers have founded out coat protein pIII on E4 can be modified to increase the binding affinity of the virus for the CNTs, without losing the initial function, that is to grow iron phosphate nanowires by modifying coat protein pVIII which serves as a template.


Fig.3 E4 and its modification sites 
Performance of E4

Researchers have done experiment to test the performance of the virus. The result has revealed that when compared with ‘one gene system’, firstly the ‘two gene system’ batteries come up with less polarization, which means resistance drops and current flow increases. Secondly, the capacity retention is outstanding, that is stable performance after many times of recharging. Thirdly, fewer CNTs are needed. Lastly, materials that have not been disregard to be good electrodes due to their low electro-conductivity in the past may now be re-examined. For example iron phosphate is non-toxic and cheap material to make electrodes, however it has a very slow reaction rate. But now with the help of virus it can be used as nanowires.

Conclusion

In summary, this article has reported the advancements of virus-drive lithium ion batteries. Two coat proteins on virus E4 were modified to connect nanowires with carbon nanotubes. And from experimental results the new ‘two gene system’ has greatly improved the conductivity of cathodes.

Virus-batteries with lithium are still rechargeable, but lighter, more flexible, smaller and eco-friendly than the old ones. Can you imagine one day we will have living virus in our phones, lights or even hybrid cars? 


References

Belcher AM, Ceder G, Kang K, Kim WJ, Lee YJ, Strano MS, Yi H, Yun DS, 2009, ‘Fabricating Genetically Engineered High-Power Lithium-Ion Batteries Using Multiple Virus Genes’, Science, vol. 324, no. 5930, pp. 1051-1055

Chiang YM, Chung SY, Delduco DF, Humphreys ES, Jagota A, Lustig SR, Parker KN, Rizzo NW, Subramoney S, Wang H, Wang S 2003, ‘Peptides with selective affinity for carbon nanotubes’, Nature, vol.2, pp. 196-200

Johnson, RC 2006, ‘Living viruses create flexible battery film’, Electronic Engineering Times, issue 1419, pp.38

Trafton, A 2009, ‘New virus-built battery could power cars, electronic devices’, MIT News, 2 April, viewed 15 March 2012, <http://web.mit.edu/newsoffice/2009/virus-battery-0402.html>

Pictures source:
Fig.3 Chiang YM et.al. 2003 http://www.ncbi.nlm.nih.gov/pubmed/12612679 

By Ivy Wong

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