Researchers at University of Limerick have found out that applying pressure to a protein found in tears and egg whites can yield electricity.
The research team from the Bernal Institute noticed that crystals of lysozyme, a model protein that is plentiful in egg whites of birds as well as in the saliva, tears and milk of mammals can produce electricity when pressed. Their research paper has been published on October 2nd in the journal, Applied Physics Letters.
The capacity to make electricity by applying pressure, known as direct piezoelectricity, is a feature of materials such as quartz that can change mechanical energy into electrical energy and vice versa. Such materials are used in a range of applications from resonators and vibrators in mobile phones to ultrasound imaging and deep ocean sonars. Bone, wood and tendon have been known to possess piezoelectricity.
While piezoelectricity is used all around us, the capacity to generate electricity from this particular protein had not been explored. The extent of the piezoelectricity in lysozyme crystals is significant. It is of the same order of magnitude found in quartz. However, because it is a biological material, it is non-toxic so it could have many innovative applications such as electroactive anti-microbial coatings for medical implants.
Aimee Stapleton, Lead Author and an Irish Research Council EMBARK Postgraduate Fellow, the Department of Physics and Bernal Institute, University of Limerick
Crystals of lysozyme are easy to create from natural sources. “The high precision structure of lysozyme crystals has been known since 1965,” said Structural Biologist at UL and Co-author Professor Tewfik Soulimane.
Professor Soulimane added, “In fact, it is the second protein structure and the first enzyme structure that was ever solved, but we are the first to use these crystals to show the evidence of piezoelectricity”.
Crystals are the gold-standard for measuring piezoelectricity in non-biological materials. Our team has shown that the same approach can be taken in understanding this effect in biology. This is a new approach as scientists so far have tried to understand piezoelectricity in biology using complex hierarchical structures such as tissues, cells or polypeptides rather than investigating simpler fundamental building blocks.
Team Leader Professor, Tofail Syed, Department of Physics, University of Limerick
The finding may have far reaching applications and could result in additional research in the area of flexible electronics for biomedical devices and energy harvesting.
Future applications of the discovery may include regulating the discharge of drugs in the body by using lysozyme as a physiologically mediated pump that searches for energy from its surroundings. Being naturally piezoelectric and biocompatible, lysozyme can serve as an alternative to conventional piezoelectric energy harvesters, many of which contain lethal elements such as lead.
Professor Luuk van der Wielen, Director of Bernal Institute and Bernal Professor of Biosystems Engineering and Design expressed his joy at this breakthrough by UL Researchers.
“The €109-million Bernal Institute has the ambition to impact the world on the basis of top science in an increasingly international context. The impact of this discovery in the field of biological piezoelectricity will be huge and Bernal scientists are leading from the front the progress in this field,” he said.
The complete paper, ‘The Direct Piezoelectric Effect in the Globular Protein Lysozyme’, by Aimee Stapleton, Mohamed R Noor, John Sweeney, Vincent Casey, Andrei Kholkin, Christophe Silien, Abbasi A. Gandhi, Tewfik Soulimane and Syed A M Tofail, is published in Applied Physics Letters.