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Swarms of dust-sized particles would explore planets

April 18, 2007
Courtesy Royal Astronomical Society
and World Science staff

En­gi­neers are de­sign­ing a new breed of plan­e­tary ex­plor­ers: ti­ny, shape-shift­ing de­vices that ride the wind like dust par­t­i­cles and al­so to com­mu­ni­cate, fly in for­ma­tion and take sci­en­tif­ic mea­sure­ments.

The specks might even be the first ex­plor­ers from Earth to vis­it plan­ets out­side our so­lar sys­tem, the de­sign­ers claim.

Swarms of so-called nano-nauts might be the first ex­plor­ers from Earth on plan­e­tary sys­tems out­side our own, re­search­ers say. De­sign­ers of the par­t­i­cles say they might be de­liv­ered to the al­ien worlds via space­crafts that use ion pro­pu­sion, a pow­er­ing sys­tem that al­lows for slow but steady accelerati­on and ef­fi­cient en­er­gy use. (Im­age cour­te­sy Cal­tech)
A “smart” dust par­t­i­cle would con­sist of a com­put­er chip about a mil­li­me­tre wide en­cased in a pol­y­mer ma­te­ri­al that wrin­kles or smooths out when elec­tri­cal­ly ac­ti­vat­ed. Wrinkl­ing the sur­face would in­crease air drag on the par­t­i­cle, mak­ing it float high­er. Smooth­ing would cause it to sink.

Sim­u­la­tions show that by switch­ing be­tween rough and smooth modes, the par­t­i­cles can grad­u­al­ly hop to­wards a tar­get, even in swirling winds, re­search­ers say.

“The con­cept of us­ing smart dust swarms for plan­e­tary ex­plo­ra­tion has been talked about for some time, but this is the first time an­y­one has looked at how it could ac­tu­al­ly be achieved,” said John Bark­er of the Uni­ver­si­ty of Glas­gow, Scot­land. He de­scribed pos­si­ble ap­pli­ca­tions of smart dust at the U.K. Roy­al As­tro­nom­i­cal So­ci­ety’s na­tion­al meet­ing in Pres­ton, U.K. on April 18.

“Com­puter chips of the size and soph­ist­ica­tion needed to make a smart dust par­t­i­cle now ex­ist,” Barker said. “We are look­ing through the range of pol­y­mers avail­a­ble to find one that matches our re­quire­ments for high defor­ma­tion us­ing min­i­mal volt­ages.” 

The specks would use wire­less net­work­ing to com­mu­ni­cate and form swarms; “we en­vis­age that most of the par­t­i­cles can on­ly talk to their near­est neigh­bours but a few can com­mu­ni­cate at much long­er dis­tances,” Bark­er added. “In our sim­u­la­tions we’ve shown that a swarm of 50 smart dust par­t­i­cles can or­gan­ise them­selves in­to a star for­ma­tion, even in tur­bu­lent wind.” The abil­i­ty to fly in for­ma­tion would enable the chips to pro­cess in­form­a­tion col­lect­ively and beam sig­nals back to an or­bit­ing space­craft, he pre­dic­ted.

To be use­ful, the par­t­i­cles would need to car­ry sen­sors. Cur­rent chem­i­cal sen­sors tend to be rath­er large for the sand-grain sized par­t­i­cles that could be car­ried by the thin Mar­tian at­mos­phere, Bark­er said. Ve­nus’s at­mos­phere, on the oth­er hand, is much thicker and could car­ry sen­sors up to a few cen­time­tres in size, so these could the­o­ret­i­cal­ly be used there now.

Mean­while, “minia­tur­i­sation is com­ing on rapid­ly,” Bark­er not­ed. Chips avail­a­ble by 2020 will have com­po­nents just a few na­no­me­tres (mil­lionths of a mil­li­me­ter) across, so that smart par­t­i­cles would be­have more like large mo­le­cules than dust grains, he ar­gued. These would-be ex­plor­ers are be­ing dubbed nano-nauts.

Bark­er’s re­search group at Glas­gow thinks it will be some years be­fore smart dust is ready to launched in­to space, he said. “We are still at an ear­ly stage, work­ing on sim­u­la­tions and com­po­nents. We have a lot of ob­sta­cles to over­come be­fore we are even ready to phys­i­cal­ly test our de­signs. How­ev­er, the po­ten­tial ap­pli­ca­tions of smart dust for space ex­plo­ra­tion are very ex­cit­ing. Our first close-up stud­ies of extra-so­lar plan­ets could come from a smart dust swarm de­liv­ered to anoth­er so­lar sys­tem.”

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Engineers are designing a new breed of planetary explorers: tiny, shape-shifting devices that can ride the wind like dust particles and also to com municate, fly in formation and take scientific measurements. The particles might even be the first explorers from Earth to visit planets outside our solar system, the designers claim. The “smart” dust particles would consist of a computer chip about a millimetre wide encased in a polymer material that wrinkles or smooths out when electrically activated. Roughening this material’s surface increases air drag on the particle, so it floats higher. Smoothing out the surface causes the particle to sink. Simulations show that by switching between rough and smooth modes, the particles can gradually hop towards a target, even in swirling winds, researchers say. “The concept of using smart dust swarms for planetary exploration has been talked about for some time, but this is the first time anyone has looked at how it could actually be achieved,” said John Barker of the University of Glasgow, Scotland. He described possible applications of smart dust at the U.K. Royal Astronomical Society’s national meeting in Preston, U.K. on April 18. “Computer chips of the size and sophist ication needed to make a smart dust particle now exist and we are looking through the range of polymers available to find one that matches our requirements for high deformation using minimal voltages.” Smart dust particles would use wireless networking to com municate and form swarms; “we envisage that most of the particles can only talk to their nearest neighbours but a few can com municate at much longer distances,” Barker added. “In our simulations we’ve shown that a swarm of 50 smart dust particles can organise themselves into a star formation, even in turbulent wind. The ability to fly in formation means that the smart dust could form a phased array. It would then be possible to process information between the distributed computer chips and collectively beam a signal back to an orbiting spacecraft.” To be useful, the particles would need to carry sensors. Current chemical sensors tend to be rather large for the sand-grain sized particles that could be carried by the thin Martian atmosphere, Barker said. Venus’s atmosphere, on the other hand, is much thicker and could carry sensors up to a few centimetres in size, so these could theoretically be used there now. Meanwhile, “miniaturisation is coming on rapidly,” Barker noted. Chips available by 2020 will have components just a few nanometres (millionths of a millimeter) across, so that smart particles would behave more like large molecules than dust grains, he argued. These would-be explorers are being dubbed nano-nauts. Barker’s research group at Glasgow thinks it will be some years before smart dust is ready to launched into space. “We are still at an early stage, working on simulations and components. We have a lot of obstacles to overcome before we are even ready to physically test our designs. However, the potential applications of smart dust for space exploration are very exciting. Our first close-up studies of extra-solar planets could come from a smart dust swarm delivered to another solar system.”