Made of freezer paper, aluminum, and tape, the badges, say the researchers, could help radiology workers or those working in the nuclear power industry better track their daily radiation exposure, enabling a faster assessment of potential tissue damage that could lead to cancer. The badges work by adding a drop of water, which activates the yeast to show radiation exposure as read by an electronic device.
“Currently, radiology workers are required to wear badges, called dosimeters, on various parts of their bodies for monitoring their radiation exposure,” says Babak Ziaie, Purdue professor of electrical and computer engineering. “They wear the badges for a month or two, and then they send them to the company that made them. But it takes weeks for the company to read the data and send a report back to the hospital. Ours give an instant reading at much lower cost.”
Workers would use the badge when in the lab and then recycle it after checking their exposure by plugging it into a device. The readout device, say the researchers, could one day be a tablet or phone.
The sensor is described as a wearable, disposable, film-type device fabricated on a paper substrate with yeast cells patterned between two electrodes and used as a smart material. It relies on the quick and measurable response of yeast to radiation – the higher the radiation dose, the greater percentage of yeast cells that die.
Wetting the badge activates the cells that are still alive to eat glucose and release carbon dioxide. The same fermentation process is responsible for brewing beer and making bread rise.
When carbon dioxide bubbles at the surface, ions also form. The concentration of these ions increases the electrical conductivity of yeast, which can be easily measured by hooking up the badge to an electronic readout system.
“We use the change in electrical properties of the yeast to tell us how much radiation damage it incurred,” says Rahim Rahimi, Purdue postdoctoral researcher in electrical and computer engineering. “A slow decrease in electrical conductivity over time indicates more damage.”
The readout system measures out in rads – the standard unit of measurement of radiation used to specify limits on how much radiation human tissue can safely absorb. For example, skin of the whole body shouldn’t be exposed to more than 7.5 rad over a three month period.
Using their badges, the researchers were able detect a radiation dose of as little as 1 millirad, which is comparable to current commercial badges. For more, see “Yeast Metabolic Response as an Indicator of Radiation Damage in Biological Tissue.”