the activity of a gene called c-fos to moni- tor the brain-cell activity of rats treated with either of two general anesthetics, propofol or pentobarbital. The anesthetized rodents exhibited increased brain-cell activity in the VLPO and decreased activity in the TMN, the same pattern seen during deep, dream- less sleep.

Propofol and pentobarbital appear to work by binding to GABA receptors on nerve cells in the TMN and elsewhere in the brain. The VLPO region doesn’t con- tain GABA receptors, however.

‘We know VLPO is being excited, but we don’t know how. We need to find that out,” says Franks.

Ultimately, Franks would like to trace the neural circuitry behind consciousness. “Understanding what leads to loss of con- sciousness is what really appeals to me,” he says. -J. TRAVIS

Getting a Grip How iecko toes stick

Geckos are the envy of rock climbers. With- out glue, suction, or claws, these lizards scamper up walls and hang from ceilings.

Scientists finally have pinned down the molecular basis of this seeming magic. Gecko feet are covered by billions of tiny hair tips, or spatulae, that hug surfaces. Temporary shifting of the electrons in the molecules of the spatulae and of oppos- ing rocks, walls, or ceilings creates adhe- sive van der Waals forces, according to a study in the Aug. 27 Proceedings of the National Academy of Sciences. The col- lective action of these subtle intermolec- ular interactions contributes to countless properties, including a liquid’s boiling point and a polymer’s strength.

Previous research had shown that gecko adhesion relies on intermolecular forces (SN: v15/00, p . 47), but scientists weren’t sure whether van der Waals bonding or water adsorption was at work. In water adsorption, a thin layer of the liquid acts like glue, but only on surfaces that readily bond water. The new study, however, shows that geckos cling equally well to water- attracting and water-repelling surfaces. Using mathematical models, the authors report that the width of each spatula is just what would be expected if van der W d s forces were operating.

The small size and high density of the spatulae, rather than their chemical com- position, enable geckos to stickto the world so well, report Kellar Autumn of Lewis and Clark College in Portland, Ore., and his col- leagues.

Gecko spatulae are made of keratin, the protein in human hair. However, when the scientists made spatulae mock-ups out of either silicon rubber or polyester, each material adhered to many surfaces as well as the real spatulae did.

“Just by splitting a surface into multiple small tips, we can get dry adhesion,” Autumn says. Such structures might serve as a new type of adhesive that doesn’t require messy, smelly liquids.

The work shows that strong adhesion can arise from what are thought to be relatively weak forces, comments Matthew Tirrell of the University of California, Santa Barbara. The highly divided gecko foot is also minutely adaptable to bumpy surfaces and is easy to reposition, he says.

A good adhesive has to both stick and release easily, adds Anthony Russell of the University of Calgary in Alberta. “Getting something to stick is not that hard,” he notes. “Getting it off and being able to use it again, that is one of the neat things that geckos have been able to do.”-K. COBB

5 a FEET FEATS Medley of gecko feet, with billlons of tiny hair tips, stlcking tightly to glass.

W W W . S C I E N C E N E W S . O R G

Electronics in the Round Mixing plastic and silicon yields form-fitting circuitry

It’s already possible to make circuitry that flexes and can even roll up like a scroll. What’s not yet available are circuits that citn conform to more-complicated surfaces, like robotic bodies and eyeball-shape cameras.

Pai-Hui I. Hsu and her colleagues at Princeton University now report taking steps toward that goal. Aiming to make a circuit that could fit closely to a spherical lens, the investigators used ordinary micro- circuit-fabrication methods to pattern arrays of silicon-based transistors onto a flat sheet of polyimide plastic that they then deformed to give it a bowl-like shape. They describe the work in the Aug. 26 Applied Physics Letters.

Such curvaceous electronic circuits may eventually lead to compact cameras with extra-wide fields of view that could be used for spying and for preventing aircraft col- lisions, says study coauthor Sigurd Wag- ner. Or, if formed into sensitive artificial skins, the new technology could lead to improved prosthetic limbs as well as robots that would be aware of their environments in more humanlike ways.

These circuits would be more versatile than today’s flexible electronics. Many devices today, from cell phones and laptop computers to automobile dashboards and aircraft instruments, contain wires and components bonded to plastic substrates that can bend without damaging the elec- tronics. Researchers also are developing flexible displays ranging from pliable liq- uid crystals that may one day adorn fabrics (SN: 6/1/02, p . 3499) to sheets of “elec- tronic paper” (SN: 4/28/01,p. 262), which are made of bendable plastic covered with electrically controlled black-and-white dots that can form patterns of letters and images.

Even so, the most flexible circuitry now available can’t form shapes that require deformation ofthe sheet, Wagner says. Get- ting circuits to conform to arbitrary shapes is “actually averytrickyproblem,” he notes.

Wagner and his coworkers came up with a trick oftheir own to solve it. By heatingthe transistor-studded polyimide flms to about 200Oc while inflating the softened surface from underneath, they created a curve. As a final step, the researchers deposited metal wires between the transistors.

In essence, the Princeton team divided the circuit into relatively strainfree transis- tor islands separated by very compliant “moats,” explains R Fabian W. Pease of Stan- ford University. “It is very original work.”

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