Power/Performance Bits: Jan. 19

Antiferromagnetic memory

Physicists at The University of Nottingham, working in collaboration with researchers in the Czech Republic, Germany, Poland, and Hitachi Europe showed that the magnetic spins of antiferromagnets can be controlled to make a completely different form of digital memory.

This was the first demonstration of electrical current control of antiferromagnets, and the first all-antiferromagnetic memory device, according to Dr Peter Wadley, from the School of Physics and Astronomy at The University of Nottingham. “This could be hugely significant as antiferromagnets have an intriguing set of properties, including a theoretical switching speed limit approximately 1000 times faster than the best current memory technologies.”

Among its unusual properties, antiferromagnets do not produce magnetic fields, so the individual elements can be packed more closely for higher storage density. Antiferromagnet memory is also insensitive to magnetic fields and radiation making it particularly suitable for niche markets, such as satellite and aircraft electronics.

In looking for a way to develop them into an independent data storage material class, the research team demonstrated that the alignment of the ‘magnetic moments’ of certain types of antiferromagnets can be controlled with electrical pulses through the material. The team’s example used CuMnAs with a very specific crystal structure, grown in almost complete vacuum.

If this potential can be realized, the researchers think antiferromagnetic memory could be an excellent candidate for a “universal memory” to replace all other forms of memory in computing.

Monitoring the brain with dissolvable sensors

A team of neurosurgeons and engineers from the Washington University School of Medicine in St. Louis and the University of Illinois at Urbana-Champaign developed wireless brain sensors that monitor intracranial pressure and temperature and then are absorbed by the body, negating the need for surgery to remove the devices.

Such implants could potentially be used to monitor patients with traumatic brain injuries, but the researchers believe they can build similar absorbable sensors to monitor activity in organ systems throughout the body.

“Electronic devices and their biomedical applications are advancing rapidly,” said Rory K. J. Murphy, a neurosurgery resident at Washington University. “But a major hurdle has been that implants placed in the body often trigger an immune response, which can be problematic for patients. The benefit of these new devices is that they dissolve over time, so you don’t have something in the body for a long time period, increasing the risk of infection, chronic inflammation and even erosion through the skin or the organ in which it’s placed. Plus, using resorbable devices negates the need for surgery to retrieve them, which further lessens the risk of infection and further complications.”

The sensor, smaller than the tip of a pencil, connects to an embeddable wireless transmitter that lies on top of the skull. (Source: John A. Rogers/University of Illinois)

The devices are made mainly of polylactic-co-glycolic acid (PLGA) and silicone, and they can transmit accurate pressure and temperature readings, as well as other information.

Having shown that the sensors are accurate and that they dissolve in saline solution and in the brains of rats, the researchers now are planning to test the technology in patients, saying that key bridges have been crossed in terms of major challenges involving size and scale.

“The ultimate strategy is to have a device that you can place in the brain — or in other organs in the body — that is entirely implanted, intimately connected with the organ you want to monitor and can transmit signals wirelessly to provide information on the health of that organ, allowing doctors to intervene if necessary to prevent bigger problems,” Murphy said. “And then after the critical period that you actually want to monitor, it will dissolve away and disappear.”