Article and graphics submitted by Dr. Umasankar Kandaswamy.
On a certain level, almost everyone is acquainted with the fact that self-blood-glucose measurement is an intrinsic and important part of a diabetic patient’s healthy life. However, only 17 million of us fully understand how heavily “living a near normal life” for a diabetic patient depends on “how effectively one can control and regulate” his or her blood glucose level. In other words, nearly 6% of the US population must self-measure the blood glucose level on a regular basis — in most cases several times a day — and adjust the insulin therapy accordingly (click here for further information on diabetes and its impact).
Since its introduction in 1970, the concept of self-measurement has grown from an obscure visual evaluation method requiring a large volume of blood (up to 25 microliters), to the use of fast and reliable electronic systems, referred to as blood glucose meters, that use electrochemical test strips to quantify blood glucose levels. Even though several types/brands of meters are commercially available for self-measurement — with options ranging from “smallest volume of blood needed” to “least amount of time taken” — no existing meter supports the option of interoperability. Simply put, if we buy a particular brand of test meter, we are forced to buy that brand’s test strips all the time. In most cases patients must endure an extensive period of trial and error before figuring out which meter/test strip combination is cost effective, easy to use, reliable, long lasting, and portable. To solve this problem, my students Kevin Mason (Electrical and Biomedical Engineering) and Zeran Gu (Mechanical Engineering) are working with me to develop a next generation smart blood glucose meter that is highly interoperable and convenient. In addition, the smart blood glucose meter is designed for compatibility with all types of mobile devices (e.g., iPad, iPhone, Android, Tablets).
The heart of the Smart Blood Glucose Meter is an electronic system called a transimpedance amplifier, which senses the electrochemical current (70 – 120 microamperes) produced by the glucose-induced reaction in a test strip and converts it to a readable voltage output (0 to 2.5V). Figure 1 shows a typical response of a transimpedance amplifier constructed in our LTU lab.
T1 instant (shown in Figure 1) is when the glucose is introduced at the test strip. After a so-called incubation period (the time period between T1 and T2), the output voltage of the amplifier starts to change in proportion to the rate at which gluconolactone (a resultant of the reaction between glucose and a mediator) is produced, thus relating the rate of change of the output voltage to the glucose concentration present in the test strip. Figure 2 shows the rate of change of the output voltage from the transimpedance amplifier for glucose concentrations ranging between 10 mg/dL to 400 mg/dL.
It can be observed that different glucose concentration levels produce output responses with distinct rise times, establishing a strong correlation between the glucose driven electrochemical reaction and the observable output voltage. Figure 3 shows the change in rise time (in seconds) for different values of glucose concentration and for three types of commercially available test strips: One-touch Ultra, Agamatrix, and Accu-Check. Experimental data shown in Figures 2 and 3 are average responses of three different sets of data collected by Kevin Mason during Spring and Summer 2012 using Electronic Explorer Kit and the Diligent-Waveforms software package.
Starting this Fall, students will be working on Phase II of the project. Phase II would involve finalizing the communication protocol (through which the transimpedance circuitry and mobile devices will communicate with each other), and developing an android/iPhone app through which the user will be able to access the device. Figure 4 shows the 3D rendering of the Smart Blood Glucose Meter designed by Natalie Haddad (student of College of Architecture, makeLab).