The world’s smallest solar panels
The world's most minute solar panel cells have been built and tested and one day in the not too distant future they could be used to power even tinier microscopic machines.
The solar panels were built by Xiaomei Jiang and her team of researchers from the University of South Florida in the States.
Their study published in the Journal of Renewable and Sustainable Energy describes how they built tiny solar panels about the size of a lower case o in 12 point font on a computer.
To make these tiny solar cells the researchers didn't simply take normal photovoltaic solar panels - the kind you might see on rooftops - and make them much smaller.
Regular solar panels are built on a brittle backing material made of silicon, similar to the sort of thing computer chips are built on. Instead, these tiny solar cells are based on an organic polymer that has the same properties as silicon, but that can be dissolved into a fluid and printed into a flexible backing material. Theoretically, this organic material could be sprayed on any surface that is exposed to sunlight.
Jiang and her team are developing these tiny panels with the hope that they will one day power a type of microscopic sensor that can be used for detecting dangerous chemicals and toxins.
These detectors are built from carbon nanotubes, the tiny cylinders of carbon that are 50 thousand times thinner than a human hair. The idea is that when the nanotubes are hooked up to a power source of around 15 volts, they can detect small amounts of particular chemicals by measuring the electrical changes that occur when chemicals enter the tubes; the exact change in charge is an indicator of what type of chemical is present.
So far, the team have put together an inch-long array of 20 of these tiny solar cells which has been enough to generate just 7.8 volts. The next step will be to optimize the cells so they produce enough power for the microscopic chemical detectors, which they think they will be able to do in the next generation of solar cells that should be ready by the end of the year.