Detection of human body odor using carbon nanotube gas sensor

Abstract

The elevating significance of the elderly's presence and social engagement in contemporary society has been highly noticed from the perspective of the aged over 65 and will surpass 20% by 2100 in developed countries including the USA, Germany, and France. Body odor in older individuals, attributed to fatty acids such as 2-nonenal and isovaleric acid, can potentially signal not only aging but also conditions like diabetes, Parkinson's disease, and liver diseases. While significant papers have been made for the development of carbon-based sensors, the detection of body odors, a highly personal and sensitive aspect, is out of the researcher’s attention it deserves, mainly due to limited societal demand. Furthermore, the endeavor to detect odors specific to the elderly demographic stands for a pioneering frontier in the field of sensor technology.

In this innovative landscape, Carbon Nanotubes (CNTs) appear as a particularly promising candidate for odor detection. In providing private health information, the most critical point of view is the availability to produce a compact size with good sensor properties. Their one-dimensional (1D) structure and expansive specific surface area make them well-suited for the sensing process. Sensitivity is of paramount importance in this endeavor, given the necessity to measure odor concentrations as low as parts per million (ppm). This is exemplified by the odor threshold of trans-2-nonenal and isovaleric acid, which stand at 4 ppm and 0.72 ppm respectively, highlighting the wide range of odor concentration levels that need to be accurately detected. The use of high-sensitivity materials like CNTs is crucial to meet these requirements. The adsorption of gas molecules onto the sidewalls and defects of CNTs leads to distinctive alterations in their electrical properties, offering a unique avenue for effectively detecting varying concentrations of odors.

Furthermore, the development CNT sensor presents exciting opportunities for real-life applications, particularly in the realm of combined sensor-personal heating systems. In personal health monitoring, for instance, they can offer valuable insights into an individual's physiological state, as certain changes in body odor can be indicative of health issues. For everyday users, the convenience of having a heating system that also keeps track of hygiene factors could significantly improve comfort and well-being.