Smart Mask Enables Real-Time Breath Biomarker Monitoring

A new smart mask integrates microfluidic and cooling technologies to continuously collect and analyze exhaled breath condensate, which could be used to provide insights into a wide range of health conditions, including chronic obstructive pulmonary disease (COPD), asthma, and COVID-19.

The mask, developed by researchers at the California Institute of Technology and named EBCare, uses a tandem cooling strategy combining hydrogel evaporative cooling and radiative cooling to effectively condense exhaled breath into liquid form, even in varied indoor and outdoor environments. This cooling method is enhanced by a ceramic-alumina-polymer hybrid metamaterial, which aids in maintaining the necessary low temperatures for efficient breath condensation. 

The captured exhaled breath condensate (EBC) is then transported through bioinspired microfluidic channels to a sensing reservoir where it undergoes electrochemical analysis on a nanoengineered electrochemical sensor array, which is ink-jet printed onto a flexible substrate, allowing for easy integration into the mask. Notably, the array can provide continuous, high-sensitivity monitoring of multiple biomarkers simultaneously, including nitrite (NO2-), ammonia (NH4+), pH levels, and alcohol; the resulting real-time data can be transmitted wirelessly to a mobile app for analysis.

In the study, the mask was able to measure biomarkers related to diet, exercise, and disease states in real-time, indicating its potential use in monitoring various health conditions. 

To find out more, we spoke with the lead author of the study, and Professor of Medical Engineering, Wei Gao.

Why focus on exhaled breath condensate (EBC) analysis?
 

This research was motivated by the critical need for comprehensive respiratory monitoring, especially in light of recent respiratory pandemics. Current methods focus largely on physical signals, leaving a gap in the ability to analyze the rich molecular information available in exhaled breath. EBC holds significant potential for revealing insights into various health conditions, but the challenges related to its collection and the lack of on-site analytical tools have hindered its widespread use. This led us to develop EBCare, a smart mask designed to overcome these barriers by enabling real-time, in situ monitoring of EBC biomarkers.

What were the main challenges in collecting and analyzing EBC through a wearable mask?
 

The main challenges we faced were ensuring efficient cooling and condensation of exhaled breath under varying environmental conditions, both indoors and outdoors, and reliably transporting the condensed liquid for real-time analysis. To address this, we integrated continuous evaporative cooling using hydrogels and radiative cooling materials, which lowered the interface temperature by approximately 7 degrees Celsius, allowing for effective on-site condensation of the breath. Once condensed, the liquid is autonomously transported to the sensor chamber by microengineered structures that create a gradient of capillary forces. This ensures precise electrochemical detection in real-time, optimizing the overall reliability and efficiency of EBC collection and analysis.

Any big eureka moments during development?
 

One such moment came when we realized that, after detection, the analyzed EBC liquid could be redirected back into the hydrogel – a breakthrough that provided a continuous water source to sustain the evaporative cooling process, ensuring the device’s ongoing operation. It was a pivotal insight that not only enhanced the system's efficiency but also allowed for continuous monitoring without needing external water replenishment, significantly improving the practicality of the wearable mask for long-term use.

How does the performance of the EBCare mask compare with traditional methods of exhaled breath condensate analysis?
 

Clinically, EBC is collected using bulky commercial condensers or specialized condensation instruments and subsequently analyzed in laboratory settings using mass spectrometry. Our device uses a tandem cooling strategy, automated microfluidics, and highly selective electrochemical biosensors to capture and analyze EBC in real time.

What applications do you foresee for the smart mask?
 

Our EBCare technology offers a wide range of real-world applications, especially in personalized medicine. It enables continuous monitoring of respiratory conditions, such as airway inflammation in asthma and COPD, and can also be applied to managing metabolic disorders. For example, we demonstrated the potential of applying our smart mask to monitor protein metabolism and kidney diseases. Additionally, EBCare provides a non-invasive solution for monitoring alcohol metabolism, making it a useful tool not only for personal health management but also for applications in law enforcement.

What are your next steps for this work?
 

The next steps involve expanding the range of biomarkers that EBCare can monitor to include those related to other respiratory and metabolic conditions. Further human trials will be conducted to validate its use in more diverse populations and settings. Additionally, efforts will be made to optimize the device for mass production and reduce costs, making it more accessible for widespread clinical and personal use. We also plan to explore the integration of advanced data analytics to enhance the interpretation of the continuous data generated by EBCare, potentially unlocking new insights into respiratory and metabolic health.

^{Image Credit: Caltech/Wei Gao and Wenzheng Heng}