System Bits: April 4

Extreme environment nanodevices; lensless imaging; nanomagnets.

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Nanodevices for extreme environments in space, on earth
Researchers at the Stanford Extreme Environment Microsystems Laboratory (XLab) are on a mission to conquer conditions such as those found on Venus: a hot surface pelted with sulfuric acid rains, 480 degrees C, an atmosphere that would fry today’s electronics. By developing heat-, corrosion- and radiation-resistant electronics, the team said they hope to move research into extreme places in the universe – including here on Earth. And it all starts with tiny, nano-scale slices of material.

Debbie Senesky, assistant professor of aeronautics and astronautics and principal investigator at the XLab, said, “I think it’s important to understand, and gain new insight through probing these unique environments.”

Professor Debbie Senesky, left, works with graduate student Caitlin Chapin on electronics that can resist extreme environments. (Source: Stanford University)

Professor Debbie Senesky, left, works with graduate student Caitlin Chapin on electronics that can resist extreme environments. (Source: Stanford University)

She suggested that by studying Venus we can better understand our own world. And while it’s hard to imagine that hot and corrosive Venus ever looked like Earth, scientists think that it used to be much cooler. Billions of years ago, a runaway greenhouse effect may have caused the planet to absorb far more heat than it could reflect, creating today’s scorching conditions. Understanding how Venus got so hot could help us learn about our atmosphere.

What’s more, devices that can withstand the rigors of space travel could also monitor equally challenging conditions here on earth, such as in our cars.

One hurdle to studying extreme environments is the heat. Silicon-based semiconductors, which power our smartphones and laptops, stop working at about 300 degrees C. As they heat up, the metal parts begin to melt into neighboring semiconductor and don’t move electricity as efficiently. Ateeq Suria, graduate student in mechanical engineering, is one of the people at the XLab working to overcome this temperature barrier. He has created an atoms-thick, heat-resistant layer that can coat devices and allow them to work at up to 600 degrees C in air. The researchers are working to improve these nano-devices, testing materials at temperatures of up to 900 C degrees.

To understand how space electronics survive for long periods of time, the XLab team tests materials, and nano-devices they create either in-house in high-temperature probe stations or in a Venus simulator at the NASA Glenn Research Center in Cleveland, Ohio. That simulator mimics the pressure, chemistry and temperature of Venus. To mirror the effects of space radiation, they also test materials at Los Alamos National Laboratory and at NASA Ames Research Center.

Further, other work at the XLab demonstrates that sensors they’ve developed could survive up to 50 years of radiation bombardment while in Earth’s orbit.

They believe if their fabrication process for nano-scale materials proves effective, it could get incorporated into technologies being launched into space. Prior to that, however, the devices could have immediate use in the automotive industry, and other fiery, high pressure earth-bound environments such as oil and gas wellbores, geothermal vents, aircraft engines, gas turbines and hypersonic structures.

A faster single-pixel camera
Compressed sensing is a new computational technique for extracting large amounts of information from a signal that is gaining more attention as of late. In one demonstration, researchers at Rice University built a camera that could produce 2D images using only a single light sensor rather than the millions of light sensors found in a commodity camera. At the same time, using compressed sensing for image acquisition is inefficient. That “single-pixel camera” needed thousands of exposures to produce a reasonably clear image.

Now, researchers from the MIT Media Lab have described a new technique that makes image acquisition using compressed sensing 50 times as efficient.

In the case of the single-pixel camera, it could get the number of exposures down from thousands to dozens, they said.

Researchers from the MIT Media Lab developed a new technique that makes image acquisition using compressed sensing 50 times as efficient. In the case of the single-pixel camera, it could get the number of exposures down from thousands to dozens. Examples of this compressive ultrafast imaging technique are show on the bottom rows. (Source: MIT)

Researchers from the MIT Media Lab developed a new technique that makes image acquisition using compressed sensing 50 times as efficient. In the case of the single-pixel camera, it could get the number of exposures down from thousands to dozens. Examples of this compressive ultrafast imaging technique are show on the bottom rows. (Source: MIT)

An intriguing aspect of compressed-sensing imaging systems is that, unlike conventional cameras, they don’t require lenses. That could make them useful in harsh environments or in applications that use wavelengths of light outside the visible spectrum. Getting rid of the lens opens new prospects for the design of imaging systems.

Guy Satat, a graduate student at the Media Lab and first author on a new paper on the subject said, “Formerly, imaging required a lens, and the lens would map pixels in space to sensors in an array, with everything precisely structured and engineered. With computational imaging, we began to ask: Is a lens necessary? Does the sensor have to be a structured array? How many pixels should the sensor have? Is a single pixel sufficient? These questions essentially break down the fundamental idea of what a camera is.  The fact that only a single pixel is required and a lens is no longer necessary relaxes major design constraints, and enables the development of novel imaging systems. Using ultrafast sensing makes the measurement significantly more efficient.” 

The research team has now detailed a theoretical analysis of compressed sensing that uses time-of-flight information. Their analysis shows how efficiently the technique can extract information about a visual scene, at different resolutions and with different numbers of sensors and distances between them.

They also describe a procedure for computing light patterns that minimizes the number of exposures.  And, using synthetic data, they compare the performance of their reconstruction algorithm to that of existing compressed-sensing algorithms. But in ongoing work, they are developing a prototype of the system so that they can test their algorithm on real data.

Nanomagnets for future data storage
With an eye toward development of new miniature data storage devices, an international team of researchers led by ETH Zurich have developed a method for depositing single magnetizable atoms onto a surface. This is especially interesting for the development of new miniature data storage devices.

Their idea is intriguing: if only a single atom or small molecule was needed for a single unit of data (a zero or a one in the case of binary digital technology), massive volumes of data could be stored in the tiniest amount of space.

Dysprosium atoms (green) on the surface of nanoparticles can be magnetised in only one of two possible directions: “spin up” or “spin down”. (Source: ETH Zurich / Université de Rennes)

Dysprosium atoms (green) on the surface of nanoparticles can be magnetised in only one of two possible directions: “spin up” or “spin down”. (Source: ETH Zurich / Université de Rennes)

This is theoretically possible, they explained, because certain atoms can be magnetized in only one of two possible directions: “spin up” or “spin down.” Information could then be stored and read by the sequence of the molecules’ magnetization directions.

Several obstacles still need to be overcome before single-molecule magnet data storage becomes a reality. Finding molecules that can store the magnetic information permanently, and not just fleetingly is a challenge, and it is even more difficult to arrange these molecules on a solid surface to build data storage carriers. To address the latter problem, an international team of researchers led by chemists from ETH Zurich has now developed a new method that offers numerous advantages over other approaches.

Christophe Copéret, a professor at the Laboratory of Inorganic Chemistry at ETH Zurich, and his team developed a molecule with a dysprosium atom at its center. Dysprosium is a metal belonging to the rare-earth elements.

Molecules with a dysprosium atom (blue) at their centre are first deposited onto the surface of a silica nanoparticle (red and orange) and then fused with it. (Source: ETH Zurich)

Molecules with a dysprosium atom (blue) at their centre are first deposited onto the surface of a silica nanoparticle (red and orange) and then fused with it. (Source: ETH Zurich)

This atom is surrounded by a molecular scaffold that serves as a vehicle. The scientists also developed a method for depositing such molecules on the surface of silica nanoparticles and fusing them by annealing at 400 degrees Celsius. The molecular structure used as a vehicle disintegrates in the process, yielding nanoparticles with dysprosium atoms well-dispersed at their surface. The scientists showed that these atoms can be magnetized and maintain their magnetic information.

ETH scientists worked with colleagues from the Universities of Lyon and Rennes, Collège de France in Paris, Paul Scherrer Institute in Switzerland, and Berkeley National Laboratory.