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

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 crashes. 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 may reach 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 concentration (BAC). 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 % BAC 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 concentration via changes in the breath’s mass without being interfered by changes in the ambient humidity, temperature and breathing pattern.