Wafiqah Zubair and Madison Gates's Senior Project: A breathalyzer that detects bacterial sinus infection

Engineering Design Projects (ES 100), the capstone course at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), challenges seniors to engineer a creative solution to a real-world problem.

Noninvasive Detection of Bacterial Sinusitis Leveraging Volatile Organic Compounds 

Wafiqah Zubair and Madison Gates, S.B. ‘26, Bioengineering and Electrical Engineering

Advisor: Haritosh Patel

• Please give a brief summary of your project.

We built a breathalyzer to detect bacterial sinus infection. Our device samples exhaled breath, uses a multi-sensor array to convert chemical patterns into electrical signals, and uses a machine learning model to predict the presence of infection. Our final prototype demonstrates rapid, non-invasive point-of-care testing to clinical decision-making.

• What real-world challenge does your project address?

There is currently no rapid, accessible point-of-care test for bacterial sinus infections. Sinusitis diagnosis in primary care relies on clinical assessment, but because symptoms such as congestion, headache, and fatigue overlap with other acute infections, this can lead to misdiagnosis. As a result, patients are often prescribed antibiotics unnecessarily, contributing to antibiotic resistance. Bacteria culture tests can be used to provide confirmation, but they can take several days to produce results, delaying appropriate treatment.

• How did you come up with this idea for your final project?

We were inspired by previous ES100 projects in the Aizenberg Lab that used electronic-nose technology for applications like lung cancer and indoor toxins. Building on this concept, we evaluated potential target diseases based on prevalence, unmet diagnostic need, and the strength of existing research linking the disease to changes in breath volatile organic compounds (VOCs). This ultimately led us to sinusitis.

• What was the timeline of your project?

We began with background research and design considerations, identifying VOCs associated with infection and selecting corresponding gas sensors. Next, we designed and tested an initial printed circuit board (PCB) using a lab setup with bubbled VOCs to validate sensor performance. We then developed a second PCB that integrated environmental sensors and a fan-based exhaust system. Finally, we simulated healthy and unhealthy breath samples, trained our machine learning model, and automated the diagnostic process through a user-friendly graphical user interface.

• What part of the project proved the most challenging?

Soldering and bringing up the second PCB proved to be quite challenging. With many moving parts, we initially had no signal from our mounted gas sensors or fan. It was difficult to determine whether the issues stemmed from PCB design, incomplete soldering, or Arduino code. We spent several days troubleshooting, but it was highly rewarding once we were able to get the fan to run and all the sensors to output meaningful data.

• What part of the project did you enjoy the most?

Integrating our CAD-designed, 3D-printed casing with the electronics and testing the system on simulated breath profiles was very rewarding. We finally had a tangible product and could see how the device can have a real-world impact.

• What did you learn, or skills did you gain, through this project?

Zubair: As a bioengineering student, I gained hands-on experience with the electrical aspects of the device. I spent a significant amount of time soldering connections, learned how to read and interpret KiCad schematics, and developed code in Arduino and Python to interface with and collect data from the sensors.

Gates: Through this project, I was able to interface with multiple engineering disciplines, including electrical, biomedical, and mechanical. In this crossover academic environment, I learned PCB and CAD design, as well as how to perform chemical testing on sensors. It was a fun challenge to design our prototype’s multi-hierarchical systems and understand how they ultimately synchronize to become a usable device.

This was our first experience working on a long-term, independent engineering project, so we learned a great deal about taking initiative, seeking help when needed, and navigating uncertainty. We also developed our ability to communicate technically complex ideas in a clear and accessible way, recently winning the Audience Choice Award at the Harvard College Writing Center’s Three Minute Thesis Competition!