As we move into the smart era, we are developing rapidly with an emphasis on the development of wearable device sensors that can monitor health condition in real time. These technological advances can check breathing, heart rate, blood pressure, and physiological phenomena in real time without going to the hospital. Among various sensing, respriation mornerting is especially important because it can possible to follow-up of chronic obstructive pulmonary diseases (COPD), moniter sleep apnea, nocturnal monitoring of respiration, unobtrusive monitoring of vital signs and prevent sudden infant and adult death syndromes. Although the contact method to measure respration rate has the advantage of greater accuracy, it is difficult to use continuously due to its inconvenience. Therefore, the development of various sensor technologies has occurred in many studies on non-contact methods.
For that, in this work, we fabracated the thin film transistor with two-dimensional (2D) nanomaterials, transition metal dichalcogenides (TMDs) which can detect change of humidity during respration. Because of their unique mechanical, chemical, and electrical properties, and large surface to volume ratio, it has good responsbility and on-off ratio. Molybdenum disulfide (MoS2) with fast absorption and easy desorption of H2O was chosen among the 2D layered materials. Although there are few report to apply respration sensor with MoS2, it is not sufficient to replace commerical respiration sensor.
So, we tried to improve the responsibility and on/off ratio with optimizaiton of crystal quality of MoS2. In addition, we tried to reduce Shottky barrier height (SBH）by appling exterial stresss of tensile and compressive. With optimization, respriation sensor has sensing time belew 0.1 sec of rising and recoversity time. It means it is sufficient to measure human respration.
After that, we tried to find out if it could be applied to lung cancer diagnosis. We prepare mice with lung cancer and monitor their respiration compared to mice without lung cancer. They found that the current values in mice with lung cancer due to volatile organic compounds such as toluene were 12.5 times higher than in mice without lung cancer.
This research will contribute to the development of new wearable devices that can monitor health conditions in real time and prevent cancer.