(J-376) Developing Polyvinylidene Fluoride-Hexafluoropropylene/Carbon Black Nanosensors to Analyze Exhaled Volatile Organic Compounds for Noninvasive Health Monitoring Applications

Introduction:: The lack of direct and accessible modes of detection for volatile organic compounds (VOCs) in complex sample types, such as breath, poses a significant challenge in point-of-care settings. To address this issue, polyvinylidene fluoride-hexafluoropropylene/carbon black (PVDF-HFP/CB) sensors were made in order to offer a sensitive and reliable solution for the real-time detection and quantification of VOCs in complex sample types, namely human breath.

Materials and Methods::

The sensors are arranged in an array and are connected to a Keithley multimeter, which is further interfaced with a computer. The development of these sensors involves fabricating them in a clean room using the photolithography process. The PVDF-HFP/CB polymer, essential for the sensors' functionality, is synthesized using a 20:1:3 ratio of PVDF-HFP, carbon black (CB), and glycerol. The PVDF is mixed with N-methyl-2-pyrrolidone (NMP) at a ratio of 1:5. Next, the sensors were tested with acetone, limonene, and isoprene individually and in a simulated mixture of VOCs at relevant concentrations of healthy breath. The concentrations used for acetone and isoprene are 0 ppm, 0.37 ppm, 4.01 ppm, and 7.99 ppm, while the concentrations used for limonene are 0 ppt, 100 ppt, 200 ppt, and 400 ppt. Specifically, experiments were run to determine the ability of the sensors to distinguish the target VOCs spiked into the simulated healthy breath mixture. These sensors were tested at four different concentrations to detect healthy to unhealthy levels of the target VOC in the simulated human breath. The response of the sensors to the VOC was recorded and analyzed using an in-house developed feature extraction algorithm.

Results, Conclusions, and Discussions::

The results of the study demonstrated that the sensors are capable of accurately detecting targeted VOCs spiked in the simulated healthy breath. Data analysis of the sensor responses provided valuable insights into the efficacy of the PVDF-HFP/CB sensors for VOC detection, notably in the sensor's ability to detect and distinguish the VOCs at their specific concentrations in a complex sample matrix such as breath. This proves their robustness in distinguishing and quantifying specific VOCs. The data exhibits that there is minimal difference between concentrations 1 and 2  for all VOCs, which represent no VOC concentrations and low VOC concentrations. This determines that, while the sensors can distinguish elevated VOC concentrations, there is minimal difference between the baseline and lower concentrations. In an effort to qualify the reproducibility of these sensors, we performed batch-to-batch variations and degradation tests. The sensors demonstrated 10% variation across multiple batches, and the degradation tests revealed that the sensors maintained 45% variation over the course of 5 days. This research presents progress in the development of portable sensors for exhaled VOC detection and indicates their potential for non-invasive breath analysis and disease detection applications.

 

Acknowledgements (Optional): : Special thanks to my mentors, the NSF-REU program, and the INDI Nanotechnology Laboratory for the opportunity to participate in undergraduate research.

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