In the U.S., one in five of the 37 million adults who has diabetes doesn't know it. Current methods of diagnosing diabetes and prediabetes usually require a visit to a doctor's office or lab work, both of which can be expensive and time-consuming. Now, diagnosing diabetes and prediabetes may be as simple as breathing.
A research team led by Huanyu "Larry" Cheng, James L. Henderson, Jr. Memorial Associate Professor of Engineering Science and Mechanics at Penn State, has developed a sensor that can help diagnose diabetes and prediabetes on-site in a few minutes using just a breath sample. Their results were published in Chemical Engineering Journal.
Previous diagnostic methods often used glucose found in blood or sweat, but this sensor detects acetone levels in the breath. While everyone's breath contains acetone as a byproduct of burning fat, acetone levels above a threshold of about 1.8 parts per million indicate diabetes.
"While we have sensors that can detect glucose in sweat, these require that we induce sweat through exercise, chemicals or a sauna, which are not always practical or convenient," Cheng said. "This sensor only requires that you exhale into a bag, dip the sensor in and wait a few minutes for results."
Cheng said there have been other breath analysis sensors, but they detected biomarkers that required lab analysis. Acetone can be detected and read on-site, making the new sensors cost-effective and convenient.
In addition to using acetone as the biomarker, Cheng said another novelty of the sensor came down to design and materials -- primarily laser-induced graphene. To create this material, the CO2 laser is used to burn the carbon-containing materials, such as the polyimide film in this work, to create patterned porous graphene with large defects desirable for sensing.
"This is similar to toasting bread to carbon black if toasted too long," Cheng said. "By tuning the laser parameters such as power and speed, we can toast polyimide into few-layered, porous graphene form."
The researchers used laser-induced graphene because it is highly porous, meaning it lets gas through. This quality leads to a greater chance of capturing the gas molecule, since breath exhalation contains a relatively high concentration of moisture. However, by itself, the laser-induced graphene was not selective enough of acetone over other gases and needed to be combined with zinc oxide.
"A junction formed between these two materials that allowed for greater selective detection of acetone as opposed to other molecules," Cheng said.
Cheng said another challenge was that the sensor surface could also absorb water molecules, and because breath is humid, the water molecules could compete with the target acetone molecule. To address this, the researchers introduced a selective membrane, or moisture barrier layer, that could block water but allow the acetone to permeate the layer.
Cheng said that right now, the method requires that a person breathe directly into a bag to avoid interference from factors such as airflow in the ambient environment. The next step is to improve the sensor so that it can be used directly under the nose or attached to the inside of a mask, since the gas can be detected in the condensation of the exhaled breath. He said he also plans to investigate how an acetone-detecting breath sensor could be used to optimize health initiatives for individuals.
"If we could better understand how acetone levels in the breath change with diet and exercise, in the same way we see fluctuations in glucose levels depending on when and what a person eats, it would be a very exciting opportunity to use this for health applications beyond diagnosing diabetes," Cheng said.
Funding from the U.S. National Institutes of Health and the U.S. National Science Foundation supported the Penn State contributions to this work. Li Yang, who was a visiting scholar in the Penn State Department of Engineering Science and Mechanics at the time of the research, is the first author. A full list of funding and authors can be found in the paper.