Posts Tagged ‘MEMS’
Harvard’s Four-Cent Paper Accelerometer Could Make Motion Sensing Ubiquitous
Harvard professor George Whitesides developed the paper accelerometers using chromatography paper, tiny sliver and carbon contact pads, and vinyl stencils. The process is so cheap and easy that the sensors could be disposable.
Accelerometers are found in everything from car airbag systems to bridges to , where they basically measure the g-forces an object is experiencing. This information is relayed to other systems. In a car, for instance, acceleration forces might trigger airbags to deploy. The NFL is researching the use of to study head impacts.
Most MEMS accelerometers are silicon-based, and fabricating them takes several days of work inside clean rooms. But building the paper ones just requires some scissors, glue and thick paper, according to IEEE. The paper sensor, which is a bit larger than a dime, consists of a cantilever cut out of chromatography paper, which is used for chemistry experiments. It bends under force and stresses a carbon piece, which changes the piece's resistance. for a description of how this works.
The best thing about the paper sensors is the other types of substrates they might enable, according to Kevin Dowling, vice president for research and development at mc10, a flexible-electronics start-up in Cambridge, Mass. “If you can make such sensors on paper, you can make them on stretchable, biocompatible substrates like silicone, and then you can mimic the properties of skin,” he told IEEE.
The paper accelerometer is not as sensitive as its silicon counterparts, however; they can measure teeny forces smaller than 80 micronewtons, and the paper only reaches about 120 micronewtons. Still, it’s an impressive feat for something made out of paper — really, who even uses that stuff anymore?
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Chip-Sized Particle Accelerators Could Lead to Cancer-Fighting Ray Guns
OK, so it can’t reach the energies produced at the LHC or Tevatron, but this is still pretty impressive. Engineers at a micro-electro mechanical systems conference last week unveiled this tiny cyclotron device, which can speed argon ions down a 5-millimeter accelerator track.
The ions have 1.5 kiloelectron volts of energy and pick up another 30 electronvolts when they whiz around a 90-degree turn, as IEEE Spectrum explains. That is peanuts compared to the 3.5 teraelectron volts currently experienced at the LHC, but hey, this chip is several orders of magnitude smaller than that massive series of tubes.
Unlike most other accelerators, this device skips magnets and instead uses an electrical field to accelerate and steer its particles through a pair of electrodes.
The goal is a suitcase-sized accelerator capable of producing 1 MeV, which would make it powerful enough for a wide range of uses, according to the chip’s creators at Cornell University. Such a device could be used to make smaller scanning electron microscopes or portable ray guns to fight cancer, rather than installing particle accelerators inside hospitals, for instance: “Think of a scalpel with a proton beam coming out of it,” said Amit Lal, who worked with chip-builder Yue Shi and leads Cornell’s SonicMEMS Laboratory.
A few hurdles remain, including a more efficient way to grab ions from the 75-micrometer-wide beam. Lots of ions are lost in the transition, Shi said. But the device at least proves the concept that you don’t need humongous frozen magnets and cavernous spaces to speed up some particles.
DARPA is funding the work, which is ongoing at Cornell.
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Self-Calibrating Micro Machines For Hyper-Accurate Sensors on Chips
MEMS inherit their inaccuracy from their minuscule size and the way they are fabricated. At such small size – we’re talking sizes down to billionths of a meter – it’s not possible to ensure that MEMS are uniform. Since no two MEMS can be reliably manufactured to be exactly the same, there has to be some means of calibrating them to cancel out those incongruities. But it’s very difficult to measure distances, and especially forces, at those small levels as well, and thus far there has been no standard by which to calibrate two MEMS to function or measure exactly the same way.
The new technology, termed electro micro metrology (EMM), allows engineers to determine the force being applied to a MEMS device. EMM defines the mechanical properties of MEMS by measuring electronic properties, which are easier to measure than physical forces at that scale. By measuring a MEMS device’s capacitance, the storage of electrical charge, researchers are able to figure out the shape, stiffness, and force being exerted by or on the device with precision.
More precise, self-calibrating MEMS mean better and cheaper atomic force microscopes, extremely sensitive sensors for sniffing out chemical threats, high-powered lab tools enabling more effective biotech and nanotech research, and perhaps even a super-sensitive “nose-on-a-chip” that can track or identify criminal suspects.
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Micro-Supercapacitors Could Boost Lifetime of Portable Devices
The new micro-supercapacitors have at least double the energy storage density of the best supercapacitors
Batteries can store electrical energy in chemical reactants and typically have higher energy storage densities than supercapacitors. But supercapacitors simply store energy as electrical charge and can endure a charge-discharge cycle millions of times, compared to just several thousand cycles for batteries.
"We have known for some time that supercapacitors are faster and longer-lasting alternatives to conventional batteries, so we decided to see if it would be possible to incorporate them into microelectronic devices and if there would be any advantage to doing so," said Yury Gogotsi, a materials engineer at Drexel University in Philadelphia.
Gogotsi worked with John Chmiola, a chemist at the Lawrence Berkeley National Laboratory. They etched electrodes made of monolithic carbon film into a conducting substrate of titanium carbide, and created micro-supercapacitors with an energy storage density at least twice as much as existing supercapacitors.
That suggests micro-supercapacitors can more efficiently store energy within ever-smaller physical spaces. By directly integrating the supercapacitors with the devices they power, researchers can boost the density of microelectronic devices and allow for more functionality, less complexity and enhanced redundancy.
The almost infinite cycle life of micro-supercapacitors would make them ideal for capturing and storing energy from renewable resources, and for on-chip operations to make electronic devices longer lasting, according to Chmiola.
More short-term applications would likely combine micro-supercapacitors with micro-batteries for the most possible energy storage. But the researchers eventually hope to boost super-capacitor storage to levels closer to batteries, and hold onto the supercapacitor edge regarding charge-discharge cycles. The looks bright indeed -- and we can think of a which could use more juice while doing recon.
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