System Bits: Aug. 12

University of Michigan researchers are developing wearable technology for disease monitoring; scientists from the Paul Scherrer Institute, the Chinese Academy of Science and EPFL have demonstrated a spin-based topological insulator.

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Wearable, continuous disease monitoring
A new wearable vapor sensor being developed at the University of Michigan could one day offer continuous disease monitoring for patients with diabetes, high blood pressure, anemia or lung disease, according to researchers there.

The new sensor, which can detect airborne chemicals either exhaled or released through the skin, would likely be the first wearable to pick up a broad array of chemical, rather than physical, attributes. U-M researchers are working with the National Science Foundation’s Innovation Corps program to move the device from the lab to the marketplace.

Each of these diseases has its own biomarkers that the device would be able to sense: for diabetes, acetone is a marker, for instance. Other chemicals it could detect include nitric oxide and oxygen, abnormal levels of which can point to conditions such as high blood pressure, anemia or lung disease.

The researchers believe their device is faster, smaller and more reliable than its counterparts, which today are much too big to be wearable. The new sensor can also detect a broader array of chemicals. Beyond disease monitoring, the sensor has other applications. It would be able to register the presence of hazardous chemical leaks in a lab, or elsewhere, or provide data about air quality.

To create their technology, the researchers took a unique approach to detecting molecules. While nanoelectronic sensors typically depend on detecting charge transfer between the sensor and a molecule in air or in solution, previous techniques typically led to strong bonds between the molecules being detected and the sensor itself. That binding leads to slow detection rates. So instead of detecting molecular charge, the engineers used a technique called heterodyne mixing, in which the interaction between the dipoles associated with these molecules and the nanosensor at high frequencies is examined.

This technique, made possible through the use of graphene, results in extremely fast response times of tenths of a second, as opposed to the tens or hundreds of seconds typical in existing technology and increases the device’s sensitivity. The sensor can detect molecules in sample sizes at a ratio of several parts per billion.

Spin-based material tested
Spintronics is a new field of electronics, using electron spin rather than motion, which requires insulating components that can control this quantum property. Scientists from the Paul Scherrer Institute, the IOP (Chinese Academy of Science) and Hugo Dil’s team at EPFL, have demonstrated experimentally, for the first time, that samarium hexaboride (SmB6) is a topological insulator.

Unlike other topological insulators, SmB6’s insulating properties are based on a special phenomenon called the ‘Kondo effect’ that prevents the flow of electrons from being destroyed by irregularities in the material’s structure, making it a very robust and efficient topological ‘Kondo’ insulator.

Researchers Hugo Dil and Nan Xu with their lab equipment at the Paul Scherrer Institute (Source: EPFL)

Researchers Hugo Dil and Nan Xu with their lab equipment at the Paul Scherrer Institute
(Source: EPFL)