A research team led by Prof. ZHANG Zhirong from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences developed a novel sensor that enables simultaneous, highly sensitive detection of multiple stable heavy isotopes in exhaled carbon dioxide (CO₂).

The findings were recently published in Analytical Chemistry.

Breath analysis has become an increasingly attractive tool in medical diagnosis due to its non-invasive, safe, and fast nature. Among the various markers in exhaled breath, CO₂ and its stable isotopes play a key role—particularly in tests, such as the ^13C-urea breath test, which is widely used to detect Helicobacter pylori infections. However, traditional hollow waveguides restricts the interaction between light and gas molecules and reduces measurement sensitivity.

In this study, the researchers introduced a novel mid-infrared enhanced hollow waveguide (EHWG) sensor. 

"The inspiration came from advanced optical techniques," said Prof. ZHANG. "We incorporated high-reflectivity mirrors into the waveguide structure."

The new sensor is capable of simultaneously analyzing multiple isotopes in exhaled CO₂ with greater precision than previously achieved. Its performance was validated using real breath samples, showing strong consistency with results from standard hospital tests. This validation underscores the sensor's potential for clinical applications.

Beyond enhanced sensitivity and reliability, the EHWG sensor is compact, lightweight, and requires small sample volumes, making it a promising candidate for next-generation breath diagnostic devices. Its portability and efficiency could facilitate its use in a wide range of medical settings, from clinical diagnostics to point-of-care applications.

"This study demonstrates that EHWG has great potential in manufacturing miniaturized, broad-spectrum, and lightweight gas sensors," said Prof. ZHANG. "It is expected to become the first choice for small-volume sample gas measurement."

Schematic illustration of the enhanced hollow waveguide gas isotope sensor. (Image by HUANG Wenbiao)