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 US population must self-measure the blood glucose level on regular basis, in most cases several times a day, and adjust the insulin therapy accordingly.
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 25mL), to a fast, reliable electronic system, referred to as blood glucose meters, that uses electrochemical test strips to quantify the 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” – none of the existing meters support the option of interoperability. Simply put, if we buy a particular brand test meter, we are forced to constantly buy that brand’s test strips. In most cases patients have to go through 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, Dr. Kandaswamy and his students, namely Kevin Mason (Electrical and Biomedical Engineering) and Zeran Gu (Mechanical Engineering), are working on developing the next generation smart blood glucose meter that is highly interoperable and convenient. This meter is designed in a way that it is compatible with all types of mobile devices (e.g., iPad, iPhone, Android).
The Heart of the Smart Blood Glucose Meter is an electronic system, commonly referred to as a transimpedance amplifier, that senses the electrochemical current (70 – 120 mA) produced by the glucose induced reaction in the test strip and converts it into a readable voltage output (0 to 2.5V). Figure 1, shows a typical response of the transimpedance amplifier constructed in an LTU lab. T1 instant (shown in Figure 1) is when the glucose is introduced on the test strip. After what is typically referred to as an incubation period (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 output voltage to glucose concentration present in the test strip.
Figure 2 shows the rate of change of the output voltage of transimpedance amplifier for glucose concentrations ranging between 10 mg/dL and 400 mg/dL. It can be observed that different glucose concentration levels produce output responses with a distinct rise time, establishing a strong correlation between glucose driven electrochemical reaction and observable output voltage. Experimental data shown is Figure 2 is the average response of three different sets of data collected by Kevin Mason during the spring and summer months of 2012 using the Electronic Explorer Kit and Diligent-Waveforms software package.
Starting this fall, students will work on Phase II of the project. Phase II would involve finalizing the communication protocol (through which transimpedance circuitry and a mobile device will communicate with each other) and developing an Android/iPhone app through which the user will be able to access the device. Figure 3 shows the 3D rendering of the Smart Blood Glucose Meter designed by student Natalie Haddad in the makelab of the College of Architecture and Design.