Breath test that contains silicon microsensors can detect cancer

An international collaboration involving researchers at École Polytechnique Fédérale de Lausanne (EPFL; Switzerland) worked to develop a portable device that can detect the presence of head and neck cancer in people's breath. The new device, equipped with extremely sensitive sensors, has been tested on patients and operates with a computer or a smartphone.

Related: Noninvasive medical breath analysis with sensitive IR spectroscopy

At SAMLAB (Neuchâtel, Switzerland), under the direction of Nico de Rooij, a team of researchers including Frédéric Loizeau, a doctoral student at the time, developed very precise microsensors able to distinguish the breath of a healthy patient from that of a sick one. The scientists' starting point was the observation that human breath contains not only air, but also hundreds of volatile organic compounds (VOCs) whose presence and concentration vary depending on the patients' state of health. The metabolism of cancer cells is different from that of healthy cells, and the two types of cells produce different substances in terms of both quantity and typology. As a result, they leave their "signature" in people's breath.

Each microsensor comprises a 500-µm-diameter silicon disk that is covered by a polymer and suspended by four minuscule "bridges" with integrated piezoresistors. When exposed to a gas, the polymer absorbs certain molecules and the disk changes shape. This deformation is detected by the four piezoresistive bridges, which emit an electrical signal. This phenomenon makes it possible to determine the signature of the gas and its concentration. The trick lies in using different polymers on each sensor to obtain an overview of the gas composition.

"There are already methods for detecting molecules called 'electronic noses' on the market. But they have a hard time analyzing very complex gases like human breath," says de Rooij. "Humidity in particular can disrupt the reading, leading to false positives or false negatives." With the new sensors, the detection process becomes extremely accurate.

With the collaboration of the Swiss Nanoscience Institute of the University of Basel, the EPFL researchers were able to test their device on actual patients from the University Hospital of Lausanne who were either sick or had undergone surgical treatment for head and neck cancer. The results of these tests showed that the sensors were incredibly effective.

A Neuchâtel-based company has already expressed interest in marketing this technology, which has been patented.

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