From solar power to hydroelectricity to evaporation, there are plenty of sustainable energy sources out there that are worth exploring. One that we have not personally come across before? Human tears. That’s the basis for new research from scientists at the Bernal Institute at the University of Limerick in Ireland, who have found that a protein present in our tears — as well as saliva, milk, and bird egg whites — can be used to generate electricity when pressed.
“In our research, we were looking at the property of piezoelectricity in a protein called lysozyme,” Aimee Stapleton, one of the researchers on the project, told Digital Trends. “Piezoelectricity is a property of some materials, whereby if you squeeze them, an electric charge, or electricity, is generated. We know a lot about how piezoelectricity works in standard piezoelectric materials like quartz, but know a less about how it works in biological materials. From the study of traditional piezoelectric materials, we know that having a certain type of crystal structure is important and we were interested to see if the same was true for proteins. So, we grew crystals of lysozyme and found that if we apply pressure to them they produce an electric charge.”
Stapleton said that the team is currently looking for real-world applications for this research. One as-of-yet unexplored avenue might involve finding some specific use case for lysozyme’s unique antibacterial and electricity-producing properties. For example, it may be useful as an energy harvester to support the functionality of biomedical devices such as pacemakers; especially since traditional piezoelectrics are often toxic — as is the case with lead.
Another possible use would involve the creation of a device able to control the release of drugs in the body by using lysozyme as a physiologically mediated pump which works by scavenging energy from its surroundings. Personally, we just like the idea of being able to squeeze out a few tears to recharge a smartphone which has died at an inopportune time!
A paper describing the work, titled “The Direct Piezoelectric Effect in the Globular Protein Lysozyme,” was recently published in the journal Applied Physics Letters.