SPINACH POWER

NEXT TIME you're eating lunch at your desk, consider this: a laptop powered by a spinach sandwich. Massachusetts Institute of Technology researchers have figured a way to harness the energy conversion prowess of the vegetable every kid hates. Leafy green plants, like spinach, are extremely efficient machines for converting sunlight into energy. Scientists have had difficulty using plant proteins that control photosynthesis because plant cells need water and salt to survive for more than a few hours. And water and salt are anathema to electric circuits. The solution turned out to be a membrane of peptide surfactants, basically soap. MIT bioengineer Shuguant Zhang manipulated the peptides to form a new natural emollient that keeps the spinach proteins alive and working on a dry surface for three weeks. How? He's not sure, but Zhang thinks the peptides carry small amounts of trapped water inside them. The spinach proteins are then sandwiched between gold-coated glass and a soft, organic semiconductor. A laser beam activates the veggie power cell. Early versions converted about 12 percent of the light to power, and Zhang thinks that can be boosted to 20 percent or more by stacking additional layers atop one another. In other words, by supersizing the spinach sandwich. -THOMAS K. GROSE

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