Whomever said big things

July 17, 2002 8:36 AM

Whomever said big things come in small packages was dead on. While most of mankind focuses on building bigger homes, bigger weapons and bigger boobs the researchers at Sandia National Laboratories think small. They are working on MEMS, or MicroElectroMechanical Systems. It's amazing stuff - they're microscopic machines, with gears the size of human blood cells. For size comparisons they used pictures and videos of a mite towering over the gears.
posted by hidely (14 comments total)

Well if that's any indication of workmanship in the tech industries these days, it's no wonder tech stocks are performing so poorly. Their clean room looks infested!
posted by pracowity at 8:51 AM on July 17, 2002

The gears look so delicate. Excellent post, thanks!
posted by riffola at 8:55 AM on July 17, 2002

Wow, the movies are fantastic .. and they load with amazing speed. Thanks for the post.
posted by rotifer at 8:58 AM on July 17, 2002

The pictures are indeed incredible, but my eyes glazed over quickly trying to read and comprehend the overview. Can anybody explain (without all the extra syllables) what they are trying to do with these teensy little gears on the teensy little chips?
posted by yhbc at 9:00 AM on July 17, 2002

Nice link, but this isn't exactly new... I remember seeing these images fully four years ago.
posted by hmgovt at 9:14 AM on July 17, 2002

I eagerly await the age of hygienic nano-maintenance: friendly little personal nanobots which swarm all over -- and inside -- you like bacteria; cleaning your teeth, trimming your nails, killing unfriendly pathogens around cuts and orifices, and metabolizing unpleasant B.O. into irresistibly seductive pheromones. The future is upon us!
posted by brownpau at 9:25 AM on July 17, 2002

I find the contrast between the manmade machinery and the "organic machinery" pretty intriguing
posted by zerolucid at 10:18 AM on July 17, 2002

hey, just saw this :) the second law of thermodynamics might not always apply on a smaller scale! "as thermodynamic systems become smaller, the probability that they will run 'in reverse' increases"
posted by kliuless at 10:35 AM on July 17, 2002

yhbc in a nutshell they have combined mechanical sensors/tools in the same package as the IC chip that reads/drives the sensors/tools. They are able to use the process of manufacturing IC chips in a way other than it was intended to create something innovative with amazing possibilities.

The overview page talks about two things- accelerometers and micromirrors. The accelerometers are capable of sensing movement/vibration in the X,Y, and Z planes through mechanical sensors in the chip. The chip itself has analog to digital conversion so the chip can read information from the sensors, process that information, and send out a signal to another device. Before this technology the chip and the sensors would be in separate packages, hence taking up more space and increased production cost.
The micromirrors on the other hand illustrate how building in this scale, in planes (X,Y), they were able to move in the third plane (Z). The microengine is connected directly to the electronics of the chip. Microtransmission gears increase the torque of the engine. A linear actuator is connected to the gears, converting the rotation into push/pull movement. The mirror is triple hinged, so pushing against the side will cause the mirror to fold and rise into the Z plane out of the X,Y planes. They state on another page Potential applications of this technology include use of these plates to reflect a light beam capable of triggering or activating sensors and other circuitry when the plates, or mirrors, are elevated to a precise position. That page also has a link to some movies of micromirrors.
posted by sailormouth at 11:04 AM on July 17, 2002

hey, just saw this :) the second law of thermodynamics might not always apply on a smaller scale! "as thermodynamic systems become smaller, the probability that they will run 'in reverse' increases"

Sounds dramatic, doesnt it? The truth is that the second law has always been an ensemble theory. The Fluctuation Theorem is merely a formalization (though an ingenious one) of the granular and random nature of equilibrium states at small enough scales.
posted by vacapinta at 12:22 PM on July 17, 2002

Nice link, but this isn't exactly new... I remember seeing these images fully four years ago.
posted by hmgovt at 9:14 AM PST on July 17

sorry - you saw this on me-fi? eep - i'll remember to do a search before posting next time.

AS for it's applications? well think about what we can do surgically with tools this small.
posted by hidely at 1:40 PM on July 17, 2002

Other likely applications: microscopic surveillance/area denial tools used by the feds and military. Brave new world.
posted by hmgovt at 4:49 AM on July 18, 2002

Just remembered, New Scientist carried an article about possible power sources for future MEMS technology. Seems regular batteries just don't shrink sufficiently well. Loading MEMS up with microscopic nuclear energy sources is a more effective means of juicing them up for extended periods. Brave new irradiated world.

Invasion of the nanonukes

New Scientist vol 172 issue 2318 - 24 November 2001, page 30


How do you power a horde of tiny machines no bigger than a grain of rice? Justin Mullins meets the engineers who are turning to the nuclear option


WHEN NASA's Cassini probe blasted off in October 1997, hundreds of protesters gathered outside Cape Canaveral to demonstrate against the launch. The problem was 150 kilograms of plutonium packed into the craft's nuclear batteries. During Cassini's long journey into the icy depths of space, the plutonium would be needed to produce several hundred watts of power. But should the launch fail, or should NASA miscalculate the trajectory of the craft as it returned to fly past Earth in August 1999, the spacecraft could be destroyed and the plutonium released into the atmosphere.

In the event, everything went without a hitch. But now the anti-nuclear protesters who gathered to send Cassini on its way have something else to worry about. Engineers making the tiny silicon-based devices known as MEMS�microelectromechanical systems�are also looking for a power source for their creations. And some think nuclear batteries could be just the thing.

MEMS will be created by the billion. And even if only a small proportion of them are nuclear powered, this could mean hundreds of thousands or possibly millions of nuclear batteries being used in all kinds of places. Some MEMS devices are even being designed to be spread on the wind like dust. Most worrying of all, there is little consensus on how and where these batteries should be used. And if they are distributed widely, what are the potential consequences for the environment and our own health?

The idea of carving tiny machines from silicon to work as sensors and actuators was dreamed up in the late 1950s by the Nobel prizewinning physicist Richard Feynman. Today MEMS are appearing everywhere from motion sensors to computer joysticks and accelerometers. With the potential global market estimated at up to $14 billion a year, even the most pessimistic believe that MEMS devices will soon have a major impact on our lives.

But these tiny machines are greedy for power. That shouldn't be a problem in applications where they can be linked to the electricity mains, or to power supplies such as a car engine. But many of their potential uses are in places where power is hard to come by. MEMS-based pressure sensors in smart tyres, for example, will have to work for years, broadcasting data at regular intervals. For this, conventional power sources such as bulky batteries simply won't do.

"The physics is working against you," says Paul McWhorter, a MEMS expert at MEMX, a New Mexico company that designs optical switches based on MEMS. The power that a battery can provide depends on its volume, and it drops dramatically as devices get smaller. The major drain for many MEMS sensors is transmitting the data they produce. "It takes a finite amount of power to broadcast data over a certain distance and that doesn't change with the size of your device," says McWhorter.

One solution is to siphon energy from the environment, a trick perfected over 200 years ago by the Swiss clock maker Abraham-Louis Perrelet, who invented the self-winding watch. In July this year, Stephen Beeby at the Department of Electronics and Computer Science at the University of Southampton unveiled the 21st-century version of Perrelet's idea: a device a little larger than a sugar cube that picks up the vibrations from its surroundings, absorbs their energy, and turns it into electrical power. The MEMS device is essentially a magnet on a minute springboard inside an inductive coil. Twang the springboard and the movement of the magnet induces current in the coil. With a number of springboards of different resonant frequencies, the device can siphon power from a wide range of ambient vibrations. It can produce up to 1.5 milliwatts, which is more than enough for many applications, says Beeby.

His ambition is to harness vibrational energy to power sensors buried deep inside engines or embedded in the fabric of bridges or roads. Most of the time these devices would be dormant, simply absorbing energy from their surroundings. Then, when enough power had been stored, they would wake up, make a measurement, and broadcast it to a receiver.

Beeby's devices could even harness the energy of human movement, like the self-winding watches that inspired them. Gilbert Schiltges, a mechanical engineer with Disetronic Medical Systems in Burgdorf, Switzerland, suggests that within five years his company's insulin-delivery devices, which are themselves no bigger than a credit card, could be powered in this way. This would remove the need for expensive batteries that now have to be replaced every three or four weeks. Pacemakers are another potential application.

A similar idea is being pursued by Wen J. Li and his colleagues at the Advanced Microsystems Laboratory at The Chinese University of Hong Kong, using a traditional helical spring. Their device is currently under wraps while the team applies for patents. An array of them could one day recharge a mobile phone, Li suggests.

Another promising non-nuclear power source for MEMS is sunlight. At the University of California, Berkeley, Kris Pister is creating "smart dust". Each mote is a silicon sliver designed to take a reading from its surroundings, process it, and beam the data out for collection. It can also pass the data on to its neighbours so the cloud can act like a distributed network of processors. He envisions releasing them like dust into the environment to keep watch for chemical and biological weapons, or monitor growing conditions on farmland. He has already tested a "cloud" of 800 motes, each just 5 millimetres across, that measure temperature and relay the data back to him.

The trouble with solar power is that the energy yield is limited by the surface area receiving sunlight. So as MEMS get smaller�eventually Pister hopes each mote will be less than 2 millimetres across�output drops dramatically. At the moment, Pister's motes are powered by tiny solar panels only a few millimetres square. "Outdoors I can generate 100 microwatts per square millimetre but indoors it's only 1 microwatt," he says. And 1 microwatt is just 5 per cent of the power he needs, which means each device must sleep for 95 per cent of the time, storing energy until it has enough to take a measurement and transmit the results.

These devices' thirst for power is pushing Pister towards the nuclear option. "We are about to start a project looking at radioisotope thermal generators," he says. Just a cubic millimetre of polonium-210 produces 1 watt of heat and has a half-life of 138 days. Other isotopes produce less energy but last far longer. Nickel-63, for example, has a half-life of a century, but generates just 1 per cent of the power of polonium-210. But even if more than 90 per cent of this energy is lost in the conversion to electricity, such a power source could change the landscape for MEMS designers. "The amount of power available is awesome," says Pister.

At the University of Wisconsin-Madison, Jake Blanchard and his colleagues have built a number of nuclear microbatteries, funded by almost half a million dollars from the US Department of Energy. Forty years before Cassini blasted off, the US Navy tested large nuclear batteries as power sources for remotely operated buoys. Now Blanchard is investigating a more refined�and much smaller�MEMS version.

He is currently testing a battery that generates current by bombarding a tiny semiconductor diode with beta radiation�high-energy electrons, in other words. The diode is made up of two layers of silicon: one, called n-type material, is doped with an element that gives it an excess of conducting electrons, while the other, called p-type material, has a deficit of electrons. When beta radiation strikes the junction, it knocks electrons out of the n-type material which then flow across the junction. This is similar to the way photons generate a current when they hit photovoltaic materials.

To squeeze as much current as possible from the device, Blanchard needs to maximise the area of the diode in contact with the radioactive material. This is tricky because solid radioactive materials are difficult and dangerous to shape on this scale. So he uses a liquid made with the beta-emitting isotope nickel-63, which he pours into a series of fine channels in the top of the chip. The resulting microbattery (see Diagram) produces only a few nanowatts, but it proves the principle works, Blanchard says.


Micro-nuclear batteries


The next step should be to raise the power output, but this is difficult. Silicon begins to break down when the energy of the electrons hitting the lattice rises above 250 kiloelectronvolts (keV). While nickel-63 produces electrons with a maximum energy of 66.9 keV, there are few other isotopes that won't damage the silicon.

So Blanchard intends to go back to the more conventional approach, and simply transform the heat created by radioactive decay into electricity. To do this he uses thermocouples�devices in which two junctions, each made from a pair of dissimilar conductors, are held at different temperatures. The output is determined solely by the temperature difference between the junctions, so thermocouples can run with any radioactive material regardless of the energy of the particles it emits. "You can get fantastic amounts of energy out of these devices," says Pister.

So far, Blanchard's prototype of this simple device produces a few tens of nanowatts. This is by no means enough for Pister's purposes, but it should be possible to scale it up by increasing the number of junctions in each device, says Blanchard.

The few environmentalists aware of the work are unconvinced that nuclear generators will ever be a practical power source for MEMS. "This has more to do with [scientists'] desperation to promote nuclear technology than any genuine breakthrough," says Karl Grossman, an anti-nuclear campaigner and author of The Wrong Stuff: The space program's nuclear threat to our planet. "I sympathise with their problem, but this is dangerous stuff. Do we really need to take these risks?" he asks.

Blanchard insists that the risks are negligible. His minuscule batteries are designed so that the nuclear material cannot escape and he is adamant that anyone unfortunate enough to breathe in or swallow one would receive a total radiation dose well within recommended safety limits. "We've paid special attention to environmental concerns, which is why we're not trying to boost the power at this stage," says Blanchard.

But will the public accept them as safe? Perhaps it will be possible to sell the idea of MEMS-based nuclear batteries as power sources for small hand-held devices such as computers or PDAs. But Blanchard also talks about using nuclear microbatteries for powering MEMS devices similar to Pister's, and sprinkling them "like breadcrumbs" onto battlefields to detect chemical weapons, for example. Tiny nuclear-powered sensors could also be mixed with oil or grease and added to the lubrication system in heavy machinery to detect when maintenance is needed. "Our batteries would work well for devices that must have a really long life. We could build them now if there was the demand," Blanchard says. So what about the protesters? Are they already up in arms at the prospect of nuclear batteries being scattered far and wide? "I expected to get opposition to the idea," says Blanchard. "But I haven't heard a single complaint."

Nevertheless, Pister intends to be cautious. "I wouldn't want these things spread around my planet," he says. "But I wouldn't mind them on other planets." One promising application for nuclear microbatteries is to power swarms of nanospacecraft that could be released into the atmosphere of Mars or Venus, or put into orbit around the Earth. Their power source would allow scientists to build up a picture of environmental conditions over huge areas of a planet or in a huge volume of space for years to come. And if a few chips were to fail, who would miss them?

"If none of this works out, the MEMS revolution will continue quite happily," says Pister. "But if we do find ways of powering these devices remotely, the applications could be bigger than all the others put together." For the moment, the public and many environmentalists remain strangely quiet about the prospect of tiny nuclear batteries being sprinkled around their planet. But they may not stay silent much longer.


Justin Mullins
posted by hmgovt at 5:09 AM on July 18, 2002

the second law has always been an ensemble theory

hey, i googled this page on the second law that makes a distinction between thermodynamic entropy and logical entropy... is that what you mean by an ensemble theory? i'm not very adept at physics :) (as in, i suck at it!)

um, i guess the bit that intrigues me is: "[u]sing Boltzmann's constant to tie together thermodynamic entropy and logical entropy is thus shown to be without basis." because like at the end of the physicsweb article it goes: "this could improve our understanding of how many small biological systems - such as 'protein motors' - work." and if life is the ability to perform a thermodynamic work cycle (and reproduce) then maybe there is a connection!? i dunno, i'm probably just confusing the two again :) /OT

microscopic surveillance/area denial tools used by the feds and military

finally, we'll be able to take on the wee beasties :) and nuke them! btw, do those mites remind anyone else of that monster thing in the hangar bay in the final fantasy movie?
posted by kliuless at 7:18 AM on July 18, 2002