Measurement of the blood alcohol concentration via a metal-phenolic film-coated quartz crystal microbalance

• Novel cylindrical mouthpieces are designed for quartz crystal microbalance breathalyzers. • The as-prepared sensor provides repeatable signal for alcohol-free breath (<5 % error) • For alcohol-free breath, the sensor is insensitive to the breath temperature and biochemistry. • Blood alcohol concentrations as little as 0.008 % are detected based on the breath’s mass. • Depending on the mouthpiece’s design, the sensitivity reaches ∼ 326–626 Hz/0.1 % BAC. Although useful to the human health at reasonable consumption, the alcohol is a psychoactive substance weakening the driving skills and contributing to daily motor vehicle incidents. The percent of fatal road accidents in some countries is very high regardless of the strict alcohol-related traffic laws, imposing the need of timely measures such as pre-driving alcohol screening via breathalyzers. All modern portable alcotesters are efficient and convenient, but they are either too expensive (e.g., the price reaches 2500 €) or require periodic calibration. The quartz crystal microbalances (QCMs) seem to be a good and inexpensive alternative, but to be implementable in alcohol sensor systems, the QCM measuring platform must maintain constant breath flow rate and breath-to-sensor distance, warranting equal gas sorption from measurement-to-measurement – a problem that remains unaddressed. Here, we disclose for the first time a series of specially-designed cylindrical mouthpieces mountable to a metal-phenolic film-coated QCM for highly-sensitive detection of blood alcohol content. The as-prepared sensor configuration transforms the turbulent exhaled air into laminar, provides steady signal for the alcohol-free breath (less than 5 % error) and discriminates up to 0.008 % blood alcohol concentration with a resolution of 0.005 %/s. Our invention could be considered as initial step towards the launch of a new generation breathalyzers detecting the alcohol content via changes in the breath’s mass without being interfered by changes in the ambient humidity, temperature and breathing pattern.