Alcohol conent measuring system based in interstitial fluid extraction and SAW sensors

A. Gnadinger, P. Gnadinger
COGNA Scientific LLC,
United States

Keywords: alcohol content, interstitial fluid, SAW sensors

Summary:

There is a need for a an easy to use, reliable, accurate and inexpensive blood alcohol content measurement system. Currently, alcohol content is measured by taking and analyzing a blood sample. This method is not user friendly. Many people shy away from pricking their finger, necessary for taking a blood sample. Other products, so called breathalyzers, measure the alcohol content in the exhaled breath of a person. Although these products are user friendly and inexpensive, they are not reliable and accurate. Attempts have also been made to measure alcohol content in the sweat or saliva of people. COGNA Scientific LLC has developed a alcohol content measurement system based on surface acoustic wave (SAW) principles to measure alcohol content in interstitial fluid. This method is user friendly, inexpensive, reliable and accurate. COGNA's product consists of a skin patch containing SAW sensors that measure alcohol content in transdermally extracted interstitial fluid, with the relevant data transmitted wirelessly to a smart phone. Currently we assume that most people carry a smart phone with them. Otherwise a smart phone is part of COGNA's product. Extracting interstitial fluid transdermally is not trivial. We use the osmotic pressure between the interstitial fluid in the body and the sensors outside the body to enhance the extraction by preconditioning the sensors with a liquid with low PH. Chemical SAW sensors have the big advantage that they can operate with a very small volume of liquid (in the microliter (┬Ál) range). SAW sensors are inexpensive since they are manufactured using IC principles but require only about three photomasking steps. Chemical SAW sensors cost about 10 cents in volume. SAW sensors are inherently very sensitive, accurate and reliable. The data extracted by the chemical SAW sensors is sent wirelessly to a smart phone. In order to minimize the transmitted data, some signal processing is required. This is done on the smart phone by proprietary software developed by COGNA and loaded onto the smart phone as an app. The relevant data (alcohol content) is then transmitted by the smart phone to any location. In order to be competitive the proposed product has to be fast (we assume that alcohol concentration has to be established within one minute), user friendly, inexpensive and reasonably small. Using chemical SAW sensors assures that these requirements are met. COGNAs product can be used by individuals, law enforcement personnel, and other parties. The app loaded onto the smart phone could also extend to functions other than minimizing he transmitted data, such as disabling the operation of a vehicle if the alcohol concentration is larger than a given threshold.