ARLINGTON, Va., Sept. 22, 2004 -- Researchers have used spinach to create a solar energy panel thin enough to coat a cell phone like green paint and recharge its batteries all day long.

To make the world's first organic solar energy panel, researchers ground up spinach leaves to extract photosynthetic proteins and related molecules that together make up a protein complex called Photosystem I. This complex converts sunlight into energy.

Solid state electronics must be kept dry, but the spinach protein complex has to be wet to function. To make the two compatible, the proteins were allowed to assemble themselves on a glass plate coated in gold and then fixed in place using two detergent-like surfactants made in the laboratory of Whitaker investigator Shuguang Zhang, Ph.D., associate director of the Center for Biomedical Engineering at the Massachusetts Institute of Technology (MIT).

"Detergent peptide turned out to be a wonderful material to keep proteins intact on the surface with electronics," Zhang said. The detergent materials may contain some trapped water, which acts like the oils that help plant seeds survive in droughts, he speculated.

The next layer is an organic semiconductor that provides a barrier between the protein complexes and the metal electronics. The finished device was then bathed in laser light.

In the presence of the light, the single layer of spinach proteins produced a small electrical current, converting about 12 percent of the light to a charge. It may be possible to raise that conversion rate to a very efficient 20 percent by sandwiching the protein complexes layer upon layer, thousands of which would be no thicker than a coat of paint. Together they would absorb more light and convert it into more energy.

These organic solar cells will not be powering cell phones or laptops any time soon, but the research does demonstrate the concept of using a plant's photosynthetic engines in solid state electronics.

Zhang's colleagues in the study, published in the American Chemical Society's NanoLetters, include Marc Baldo of MIT's department of electrical engineering and computer science, Joel Schnur of the U.S. Naval Research Laboratory, and Barry Bruce of the Center of Excellence in Biotechnology at the University of Tennessee.

Zhang discovered self-assembling peptides while working with Alexander Rich at MIT. A large part of Zhang's research focuses on various self-assembling peptide systems, which includes a peptide matrix scaffold for tissue engineering and biological surface engineering for cell pattern formation. He holds three U.S. patents and additional seven pending patents on the self-assembling peptide systems.

Zhang received a Whitaker Biomedical Engineering Research Grant in 1997 that supported his work on creating biological scaffolds that encourage nerve cell growth and networking, a very early step toward reversing paralysis.

Contact:
Shuguang Zhang, Massachusetts Institute of Technology
Frank Blanchard, The Whitaker Foundation