Day 084 - Growing batteries

Submitted by Sam on 13 August, 2011 - 02:11

Angela Belcher is a materials scientist at MIT. As a graduate student at the University of California, she elucidated the molecular assembly system by which certain molluscs create their protective shells. Shells like those of the abalone sea snail which she studied are biocomposite materials made from both organic protein (2% of the shell's mass) and inorganic calcium carbonate (98% by mass), and are created by the action of proteins encoded by genes. These particular proteins are negatively charged, and pull positively charged calcium ions from the snail's environment into layers which accrete between the proteins, forming a structure thousands of times stronger than the individual materials that compose it – abalone shells are much tougher and stronger than chalk, for instance, which is also made from calcium carbonate.

Fascinated by the interaction between living protein and its control of calcium to create a nano-engineered shell – all specified by a certain DNA sequence – Belcher recognized that any element from the periodic table could theoretically be manipulated by a corresponding DNA sequence into forming any kind of structure. By finding the appropriate DNA code, these structures could hypothetically be created from materials natural evolution had never before worked with, and coaxed into shapes never naturally occurring.

With the goal of creating DNA sequences that could code for the synthesis of any useful material, Belcher and her team started by genetically engineering a long, tubular virus through a process of selective evolution to coat itself with inorganic materials including gold and cobalt oxide. The long viruses now formed tiny lengths of nanowire, which the group was able to engineer together in 2009 to form the basic components of a powerful and compact battery. These new batteries, specified by genes that produce proteins that manipulate inorganic materials, have the same energy capacity as the latest batteries specified for powering hybrid cars.

Whilst conventional batteries generate a lot of waste during production and contain harmful materials that make clean and safe disposal a problem, the genetically engineered viral batteries produce practically no waste, growing themselves through an environmentally friendly process at room temperature, using only water as a solvent. As they are grown on an organic substrate, they are also at least partially biodegradable.

This kind of work synthesizes expertise from several disciplines, using the power of genetic engineering to produce nanotechnology applicable to the electronic world. Belcher's work shows the viability of repurposing biological processes for the construction and control of (largely) inorganic structures like virally-grown and evolutionary optimized batteries and solar cells, grown through energy-efficient and environmentally-friendly processes.

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