To be filed with a biosensor
Subcutaneous biosensor for long-term monitoring of blood alcohol
Anatoly Alizar, Geektimes, based on UC San Diego: Tiny Injectable Sensor Could Provide Unobtrusive, Long-term Alcohol Monitoring
Constant monitoring of the concentration of alcohol in the blood is an important task, the solution of which can save millions of lives. If monitoring is carried out automatically with data transmission over a wireless connection, then such a sensor can easily be connected to the car control system – and a person with a blood alcohol concentration above the permissible level will never get behind the wheel of a car again. The engine just won't start.
Moreover, at the request of the carrier, such sensors can automatically send information to law enforcement agencies and to the ambulance for automatic response to alcohol concentration limits. It is no secret that a significant proportion of serious crimes and suicides are committed under the influence of alcohol. Such monitoring will also save many lives.
Engineers at the University of California, San Diego have developed a miniature implantable biosensor of ultra-low power, which can be used for continuous long-term monitoring of alcohol. The chip is small enough to be implanted into the body just below the surface of the skin and is powered by a wireless wearable device – for example, a smartphone, smartwatch or other wearable device.
A miniature chip measuring 0.85×1.5 mm requires only 970 nanowatts to work. Data transmission is carried out by the backscattering method (the measurement time is no more than three seconds). In principle, such a small amount of energy can be extracted directly from the human body: for example, by decomposing sugar in the blood, or by the temperature difference between the internal and external circuits of the microcircuit. Or from various background sources: vibration, radio waves, etc. But in this case, the developers have implemented the simplest way to obtain energy from a permanent external transmitter, which can be any electronic gadget or wearable electronics.
"The ultimate goal of this work is to develop a permanent, unobtrusive alcohol and drug monitoring device for patients in addiction treatment programs," says project leader Drew Hall, professor of electrical engineering at UC San Diego Jacobs School of Engineering. Drew Hall also collaborates with the Center for Wireless Communications and the Center for Wearable Sensors, which work at the University of California, San Diego.
One of the problems for patients in addiction treatment programs is the lack of convenient tools for constant monitoring. The most common way to assess the level of alcohol in the blood is now breathalyzers, rather clumsy devices. To use them, you need to get in touch with the patient and ask him for assistance, which is not always possible and convenient to do. In addition, breathalyzers do not give a very accurate result, and they can be deceived. A blood test is the most accurate method, but it must be performed by a qualified specialist.
As an alternative method of measuring the level of alcohol in the blood, it was proposed to use special tattoos on the body with built-in alcohol sensors, however, they are not without drawbacks. Such tattoos are easy to remove – and they are intended for one-time use (that is, the tattoos themselves are temporary). According to the developers of the new sensor, subcutaneous injection is the most reliable option for long–term and accurate tracking of blood alcohol levels for many months and years.
Subcutaneous sensor compared to a one-cent coin and the tip of a biopsy needle with a diameter of 1.65 mm. Photo: David Baillot/UC San Diego Jacobs School of Engineering.
A biosensor chip with a volume of about one cubic millimeter is inserted under the skin into the interstitial fluid that surrounds the cells of the body. The sensor is coated with alcohol oxidase. This enzyme selectively interacts with alcohols and produces acetaldehyde and acetic acid, which can be detected electrochemically. Electrical signals are transmitted wirelessly to a nearby wearable device, such as a smartwatch, which simultaneously acts as a source of wireless power supply for the chip. Two additional sensors on the chip measure background signals and pH levels to refine alcohol concentration readings. The low-power voltage stabilizer uses amperometric and potentiometric methods with a sensitivity of 2.5 nanoamepres and 0.5 millivolts, respectively.
The chip has already been tested in the laboratory on a mixture of ethanol in diluted human serum under layers of pig skin. Now scientists are planning to conduct experiments on live pigs. The inventors have filed a patent application for this technology.
The report “A Sub-1 µW Multiparameter Injectable BioMote for Continuous Alcohol Monitoring” was presented on April 10, 2018 at the IEEE Custom Integrated Circuits Conference in San Diego.
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