Scientists keep looking for new ways forward in electronics once traditional techniques for shrinking transistors run out of gas. Researchers at Sandia National Laboratories are suddenly very excited about the possibilities of MOFs.
The acronym stands for metal-organic framework materials, which feature a crystalline structure of rigid organic molecules linked together by metal ions. MOFs have some unusual properties, one of which is an extraordinarily large surface area; one gram of a MOF, if it were stretched out, would top the square meters in a football field, says Mark Allendorf, a Sandia senior scientist studying the materials.
Another key attribute is that MOF structures have tiny holes, or pores, that molecules of other elements can be plugged into–a bit like the way tinker toys come together, Allendorf says.
Potential uses of MOFs up to now been limited, he says, because they typically work just as insulators, preventing the passage of electricity. But that is about to change, Allendorf predicts.
A new paper set to appear in Science magazine–coauthored by researchers at Sandia and the National Institute of Standards and Technology–describes some novel techniques for turning MOFs into effective conductors of electricity–which they say could greatly expand their potential uses, such as in chemical and medical sensors, energy storage and many other electronic applications.
“Imagine breath analysis that can now only be done in a doctor’s office because the machine is so large and expensive,” Allendorf says. A MOF-based equivalent, by contrast, might be the size of a quarter, he says.
The background is that circuitry in chips is shrinking to point it will eventually run into physical limits, making it harder to keep making circuitry cheaper and more capable the conventional way. MOFs make it practical to move and manipulate individual molecules–a jump to possibly the tiniest potential size for electronic components, the Sandia researchers say.
The pores in MOFs help to organize molecules, as researchers exploit the tendency of certain kinds of molecules to insert themselves into the tiny holes.
To create a structure that conducts electricity, Sandia says, the researchers coated a thin film of a MOF on a substrate with platinum electrodes patterned on its surface. The substrate was then dipped in a solution that contained a material known as tetracyanoquinodimethane, or TCNQ, whose molecules seeped into the pores on the MOF–with the film creating an electronic bridge with the platinum connection points.
One eventual goal, Allendorf says, is to create special electronic coatings that could be applied to all kinds of surfaces–like on cars or counters or furniture–for purposes such as creating sensors or storing energy.
Chip giant Intel next year expects to ship chips with circuitry measured at 14 nanometers, or billionths of a meter. The company and its rivals seem confident they can go well below 10 nanometers, but exactly how far is not clear. MOFs, by comparison, could likely scale down to 1 nanometer, the Sandia scientists say.
It’s too early to tell when MOF research might turn into products. The next step for the researchers, Allendorf says, is to keep experimenting to find the best combinations of materials and to make working circuits using the technology.
“This isn’t a one-off,” Allendorf says. “We’ve now done this several different ways, using different molecules.”
A short animation showing the links between MOF molecules is here.
For the latest news and analysis, follow @wsjd
Get breaking news and personal-tech reviews delivered right to your inbox.
More from WSJ.D: And make sure to visit WSJ.D for all of our news, personal tech coverage, analysis and more, and add our XML feed to your favorite reader.