Tips from nature

Silicon based solar devices are believed to be nearing their performance limits which are not as efficient as one would like it to be. The search for new materials and new processes to increase efficiency of collecting photons is holding out some promise.

Like the latest research at Oregon State University on harnessing tiny, single-celled marine organisms called diatoms for the fabrication of solar power devices.

Tiny, single-celled marine organisms called diatoms have rigid shells in a kaleidoscope of shapes and patterns. Making use of this structure is how the team developed a solar system.

It starts with allowing a layer of diatoms to settle on a transparent conductive glass surface. The organic matter is then removed, leaving behind the diatom shells. A biological agent is then added to create tiny particles of titanium dioxide, which form a thin layer. As the photons bounce around more inside the pores of the diatom shell, the process becomes more efficient.

From diatoms to stringing up a few viruses to make a nanowire that acts as the anode of a battery may seem a simple jump but it took a lot of perseverance to a crazy idea.

The harmless M13 bacteriophage is attracted to inorganic materials. Each virus when coated with gold and cobalt oxide is transformed into a scrap of nanowire. When these are combined, they form a film that can act as anode or the part of a battery that carries a negative ionic charge.

Charging a battery requires flow of ions from the negatively-charged anode to the positively-charged cathode and discharging needs a flow in the opposite direction.

Using viruses that would be attracted to iron phosphate and carbon nanotubes the team made a cathode which is light. They generated a micro-battery capable of around 100 charges. The prototype was inflated to the size of a button cell battery which powers a simple LED. The new virus-produced batteries are no different from traditional batteries as far as the energy capacity and power performance is concerned.

The most advantageous aspect of virus-built batteries is they could be produced in an environmentally friendly manner and they would prove economical for the manufacturers too. The manufacturing process could be carried out at or below room temperature without the involvement of the harmful organic solvents. Battery materials are non-toxic.

The team is now studying ways to develop batteries having higher voltage and capacitance by using different materials such as manganese phosphate and nickel phosphate.

As is evident, there is much in nature which can show the way in the quest for new materials and methods.