New an­ten­nas are up to a hun­dredth the size of to­day’s de­vices

Weekend Mirror - - CHILDREN’S CORNER -

An­ten­nas

just got a whole lot smaller.

Tiny chips that com­mu­ni­cate via ra­dio waves are a tenth to a hun­dredth the length of cur­rent state-ofthe-art com­pact an­ten­nas. At only a cou­ple hun­dred mi­crom­e­ters across — com­pa­ra­ble to the thickness of a piece of pa­per — these next-gen an­ten­nas can re­lay the same types of sig­nals as those used by TVs, cell phones and ra­dios, re­searchers re­port Au­gust 22 in Na­ture Com­mu­ni­ca­tions. The tech­no­log­i­cal ad­vance could pave the way to cre­ate wear­able, or even in­jectable, elec­tron­ics, says study coau­thor Nian Sun, an elec­tri­cal and com­puter engi­neer at North­east­ern University in Bos­ton.

An­tenna minia­tur­iza­tion has been stalled out for decades, so these mi­nus­cule de­vices are “a huge deal,” says John Do­mann, who wasn’t in­volved in the work.

A tra­di­tional an­tenna picks up sig­nals when elec­tro­mag­netic waves mov­ing through the air wash over it, caus­ing the an­tenna’s elec­trons to flow through it in an elec­tric cur­rent. That cur­rent cre­ates an elec­tric volt­age, es­sen­tially a read­out of what­ever mes­sage those elec­tro­mag­netic waves car­ried.

But the longer the wave­length, the longer an an­tenna must be to gen­er­ate a volt­age big enough to con­vey that mes­sage clearly, ex­plains Do­mann, a bio­med­i­cal engi­neer at Vir­ginia Tech in Blacks­burg. A con­ven­tional an­tenna typ­i­cally needs to be at least one-tenth the length of the elec­tro­mag­netic waves it’s pick­ing up. For in­stance, cell phones tuned into 11- to 15- cen­time­ter- long ra­dio waves have to con­tain an­ten­nas at least a few cen­time­ters long to get good re­cep­tion.

In the new study, re­searchers over­came that long-stand­ing size limit by fash­ion­ing an­ten­nas that use a dif­fer­ent method to trans­late sig­nals. When elec­tro­mag­netic waves pass over one of these chip an­ten­nas, the waves ac­ti­vate atoms in a layer of mag­netic ma­te­rial. Sim­i­lar to the way sport spec­ta­tors stand and sit to cre­ate waves that rip- ple across a sta­dium, the atoms switch their mag­netic align­ments back and forth to cre­ate a mag­netic cur­rent that runs through the chip.

That mag­netic cur­rent vi­brates an un­der­ly­ing layer of piezo­elec­tric ma­te­rial — a kind of ma­te­rial that gen­er­ates volt­age when bent or squeezed. Since the vi­bra­tions cre­ate much shorter waves than those from in­com­ing air­borne elec­tro­mag­netic sig­nals, an an­tenna can be much smaller and still work.

Re­searchers built tiny an­ten­nas that could com­mu­ni­cate at the ra­dio fre­quency ranges used by GPS, WiFi, FM ra­dio and broad­cast TV. These new­fan­gled an­ten­nas have “enor­mous potential,” Sun says. He imag­ines at­tach­ing them to de­vices that could be em- bed­ded in peo­ple’s cloth­ing or even in­side their bod­ies ( SN: 9/ 10/ 11 p. 10). “You can also de­sign re­ally, re­ally com­pact GPS re­ceivers,” he adds, which could help track ev­ery­thing from eas­ily mis­placed house­hold items to mil­i­tary equip­ment.

Do­mann says he’s most ex­cited about potential bio­med­i­cal uses for these an­ten­nas. “You could imag­ine some sort of a de­vice where you have an im­plantable labon-a-chip, where you have some­thing in­side of a pa­tient that can ac­tively mon­i­tor them and then re­lay in­for­ma­tion to their physi­cian in real time.”

Cap­tion: A new type of mi­crom­e­ter- thick chip could one day trans­mit sig­nals from de­vices embed­ded in our clothes or even our bod­ies.

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