Spintronic Device Uses Thin-Film Organic Semiconductor

University of Utah physicists developed an inexpensive, highly accurate magnetic field sensor for scientific and possibly consumer uses based on a “spintronic” organic thin-film semiconductor that basically is “plastic paint.”

The new kind of magnetic-resonance magnetometer also resists heat and degradation, works at  room temperature and never needs to be calibrated, physicists Christoph Boehme, Will Baker and colleagues reported online today in the Tuesday, June 12 edition of the journal Nature Communications.

The magnetic-sensing thin film is an organic semiconductor polymer named MEH-PPV. Boehme says it really is nothing more than an orange-colored “electrically conducting, magnetic field-sensing plastic paint that is dirt cheap. We measure magnetic fields highly accurately with a drop of plastic paint, which costs just as little as drop of regular paint.”
          
The orange spot is only about 5-by-5 millimeters (about one-fifth inch on a side), and the part that actually detects magnetic fields is only 1-by-1 millimeters. This organic semiconductor paint is deposited on a thin glass substrate which then is mounted onto a circuit board with that measures about 20-by-30 millimeters (about 0.8 by 1.2 inches).
          
The new magnetic field sensor is the first major result to come out of the new Materials Research Science and Engineering Center launched by the University of Utah last September: a six-year, $21.5 million program funded by the National Science Foundation, the Utah Science Technology and Research initiative and the university.

University of Utah physics professor Brian Saam, one of the center’s principal investigators, said the new magnetometer “is viewed widely as having exceptional impact in a host of real-world science and technology applications.”

Boehme is considering forming a spinoff company to commercialize the sensors, on which a patent is pending. In the study, the researchers note that “measuring absolute magnetic fields is crucial for many scientific and technological applications.”

As for potential uses in consumer products, Boehme said it’s difficult to predict what will happen, but notes that existing, more expensive magnetic-field sensors “are in many, many devices that we use in daily life: phones, hard drives, navigation devices, door openers, consumer electronics of many kinds. However, Joe Public usually is not aware when he uses those sensors.”

“There are sensors out there already, but they're just not nearly as good – stable and accurate – and are much more expensive to make,” Saam said.

Boehme believes the devices could be on the market in three years or less – if they can be combined with other new technology to make them faster. Speed is their one drawback, taking up to a few seconds to read a magnetic field.

Boehme, the study’s senior author, conducted the research with University of Utah physics doctoral students Will Baker (the first author), Kapildeb Ambal, David Waters and Kipp van Schooten; postdoctoral researcher Hiroki Morishita; physics undergraduate student Rachel Baarda; and two physics professors who remain affiliated with the University of Utah after moving elsewhere: Dane McCamey of the University of Sydney, Australia, and John Lupton of the University of Regensburg, Germany.

The study was funded by the U.S. Department of Energy, National Science Foundation, David and Lucile Packard Foundation and Australian Research Council.