Crying for Power? Your Tears Could Generate Electricity

What do egg whites and human tears have in common? According to a new study from Ireland, both materials can generate electricity, thanks to an enzyme they contain.

The enzyme, called lysozyme, is also found in saliva and mammalian milk, according to the study, which was published Oct. 2 in the Journal of Applied Physics. The enzyme is anti-bacterial; it attacks the cell walls of bacteria, weakening them.

When lysozyme is in a crystalized form, it also appears to have a property called piezoelectricity, meaning the enzyme can convert mechanical energy (when pressure is applied to it) into electrical energy, the researchers wrote.
Though the name may sound foreign, "piezoelectricity is used all around us," lead study author Aimee Stapleton, a postgraduate fellow studying physics at the University of Limerick in Ireland, said in statement. For example, piezoelectric materials such as quartz crystals are used in mobile phones (as the vibrating component) and deep-ocean sonar, according to the statement.

Indeed, materials such as bone, wood, tendons and proteins (including collagen and keratin) have piezoelectric properties, according to the study.

But "the capacity to generate electricity from this particular protein [lysozyme] has not been explored," Stapleton said.

To study the piezoelectric properties of lysozymes, the scientists applied a crystallized form of the enzyme to films. Researchers then applied mechanical force to these films and recorded the amount of electricity generated.
The researchers think that, in the future, lysozymes could be used to power biomedical devices that are used in people's bodies, the scientists wrote in the study. The enzymes could also be used to power and control the release of drugs in the body, the study said.

More research is needed, however, before the enzyme can be used for these purposes, the researchers said.