Manufacturing Bits: Oct. 28

Making graphene from cooked sawdust
The University of Birmingham has found a new and cheap way to make nanostructured carbon materials, such as carbon nanotubes and graphene.

The magic formula? Common sawdust. Sawdust is made up of cellulose and lignin. Researchers can convert this biomass material into nanostructured graphitic carbon in a single step.

Sawdust to enable graphene? (Source: University of Birmingham)

First, the sawdust is coated in iron nitrate and then cooked at 700 degrees centigrade. As a result, iron carbide nanoparticles are produced. Iron carbide nanoparticles are generated in situ by thermal decomposition, followed by a carbothermal reduction process, according to researchers.

The nanoparticles then etch through the biomass. This, in turn, generates intertwined graphitic tubes through catalytic graphitization. The pore size is dependent on the iron content. This method can also be used to produce nanocomposites of Fe3C/graphite combined with nanoparticles of metal oxides such as CaO or MgO.

In a statement, Zoe Schnepp, from the University of Birmingham’s School of Chemistry, said: “We are taking waste plant matter and making an advanced material. Waste from agriculture and industry is often costly to deal with, for example, in landfill. Industry is becoming increasingly interested in adding value to this waste and creating something useful out of things that otherwise would have been burned or buried.”

Graphene brain probes
DARPA and the University of Wisconsin at Madison have developed a graphene-based carbon-layered electrode array technology for use in neural imaging and optogenetic applications.

The technology could provide unprecedented insights into the brain structure and its function. The development is part of DARPA’s Reliable Neural-Interface Technology (RE-NET) program. The program addresses the need for neural interfaces to control dexterous functions in the area of prosthetics.

Researchers devised a graphene-based, carbon-layered electrode array (CLEAR) device. The new device uses graphene on a flexible plastic backing that conforms to the shape of tissue. The graphene sensors are four atoms thick and electrically conductive. It is transparent over a broad wavelength spectrum from ultraviolet to infrared.

Metal electrodes (top left) are opaque, obstructing views of neural tissue. DARPA has developed new graphene sensors (top middle). Placed on a flexible plastic backing (bottom), the sensors are part of a proof-of-concept tool for use in neural imaging (top right). (Source: DARPA)

The CLEAR device can be implanted on the brain surface in rodents. Researchers characterize the optical transparency of the device at >90% transmission over the ultraviolet to infrared spectrum. “This technology demonstrates potentially breakthrough capabilities for visualizing and quantifying neural network activity in the brain,” said Doug Weber, DARPA program manager, on the agency’s Web site. “The ability to simultaneously measure electrical activity on a large and fast scale with direct visualization and modulation of neuronal network anatomy could provide unprecedented insight into relationships between brain structure and function—and importantly, how these relationships evolve over time or are perturbed by injury or disease.”

Nanotubes in space
A super-black, carbon-nanotube coating will be tested on an instrument for the first time this fall on the International Space Station, according to NASA.

The coating will be used to suppress stray light in a new solar coronagraph on the space station. The coronagraph will use a single set of lenses to image so-called solar coronal mass ejections (CMEs). CMEs, which are bursts of solar material that hurdle across the solar system, could pose a hazard to spacecraft and astronauts.

The coating will be applied to a cylindrical-shaped baffle, which is a component that helps reduce stray light in telescopes. This type of coating could replace black paint, the current state-of-the-art technology for absorbing stray light in space instruments.

Goddard optical designer looking at a coronagraph (Source: Greg Card/High Altitude Observatory, Boulder, Colorado)

Currently, scientists receive coronagraphic measurements from the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory (STEREO). SOHO was launched in 1995, while STEREO has operated in space since 2006. “If one of these systems fails, it will affect a lot of people inside and outside NASA, who study the sun and forecast space weather. Right now, we have no scheduled mission that will carry a solar coronagraph. We would like to get a compact coronagraph up there as soon as possible,” said Doug Rabin, a NASA-Goddard heliophysicist, on the agency’s Web site.

The super-black carbon-nanotube coating is based on a multi-walled nanotube technology. It can absorb 99.5% of the light in the ultraviolet and visible spectrum, as well as 99.8% in the longer infrared bands. The coating has been developed by using atomic layer deposition (ALD). “Previous ALD chambers could only hold objects a few millimeters high, while the chamber (NASA-Goddard) has developed for us can accommodate objects 20 times bigger; a necessary step for baffles of this type,” said Goddard optics engineer John Hagopian.