An electronic skin-worn ‘tattoo’ composed of an integrated iontophoretic system and amperometric biosensor can specifically read and monitor blood alcohol levels in real-time.
Alcohol-related incidents and injuries have a great impact on global socioeconomic and health care costs. General drinkers, health care professionals, law enforcement officials, and the hospitality industry can monitor alcohol consumption by urine, blood, saliva, and sweat measurements, as well as verbal interview assessments. Blood alcohol concentration (BAC) is the most frequently used indicator, but it is an inconvenient and invasive means by which to gather alcohol consumption information. Breathalyzers are currently the most popular tool to measure BAC, but the reliability of measurements can be affected by humidity, temperature, traits of the user, and other environmental factors. There are transdermal devices that can measure ethanol in perspiration after alcohol consumption, but these produce results after long time delays. Accordingly, there is a demand for an alternative way to measure BAC in a non-invasive and real-time manner. To overcome some of the obstacles in alcohol consumption monitoring, a group of researchers from the University of California have developed a novel ‘tattoo’ device that can be worn on the skin and provide real-time measurements that estimate blood ethanol levels.
The ‘tattoo’ alcohol monitoring device is composed of 2 parts: a drug iontophoresis system and an amperometric (current) biosensor. Iontophoresis is the process of using an electrical current to move an ionic drug compound across the skin. The device’s iontophoresis electrodes induce the wearer to sweat by moving the drug pilocarpine through the epidermis. The amount of ethanol in the sweat is then detected and analyzed by three amperometric-sensing electrodes that form the amperometric biosensor. The system is integrated together as a tattoo-based, or skin-worn flexible electronic apparatus on temporary tattoo paper that transmits real-time current data wirelessly using Bluetooth to a mobile device or laptop. It also has enough flexibility to handle the mechanical stress of movement and the non-planar surfaces of the skin.
To evaluate the ability of the tattoo alcohol biosensor to detect on-body changes in ethanol, three subjects were recruited to test the system before and after alcohol consumption. The biosensor was placed on the inside arm of each subject and pilocarpine was delivered across the skin. After a 5 minute rest period needed to generate sweat, amperometric measurements of ethanol in the sweat measurements were taken to establish baseline (control) levels. The subject then consumed either 5 ounces of wine or 12 ounces of beer for 5 minutes, and waited 15 minutes for the alcohol to diffuse through the bloodstream and into surrounding body tissues. The iontophoresis/amperometric cycle was then conducted again to measure ethanol in their sweat. To validate sensor performance, each measurement cycle was followed by simultaneous BAC readings using a commercially-available breathalyzer.
Comparison of the on-body amperometric results shows that there was a distinct increase in current response before and after drinking alcohol. The before-drinking condition corresponded to a BAC value of 0.000%. After drinking, amperometric responses increased, and with the addition of a second alcoholic drink, produced an even larger signal. BAC values measured by breathalyzer between subjects varied, due to their differences in weight and alcohol metabolism rate. However, there was good correlation between sweat ethanol level and BAC values in the same subject, indicating that the sensor’s readings were reliable compared to an external barometer. Additional control conditions and optimization experiments were also conducted to ensure the specificity of sweat readings and that the sensor response was due solely to the consumption of ethanol.
This is the first time that researchers have combined iontophoretic technology with amperometric sensing of a metabolite on a single, wearable ‘tattoo’ device. This non-invasive alcohol monitoring system can be applied to estimate ethanol levels after the consumption of other alcoholic beverages, and future studies by the researchers will focus on personalizing the sensor to different subjects, improving calibration, and data security. The further development of this novel device as a low-cost, single-use, alcohol sensor would enhance its potential by allowing users to monitor their blood alcohol levels prior to getting behind the wheel, or as an on-the-go tool for law enforcement officials.
Written By: Fiona Wong, PhD