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device to try and solve this issue, however, she said she had problems with it. She then switched back to using the OneTouch glucose meter to prick her finger at different points throughout the day. Although this method is non-continuous, she said at the time it was a better option than the continuous monitor. “The continuous monitor was a painful process having it in and then taking it out, and the monitor was also connecting through a radio device and sometimes it would go off and wake me up at night,” she said. “I had my monitoring device, and then I had a separate site on my body where the insulin pump was, but I couldn’t shower with either of them. I would have to take them off. They told me they didn’t want me to work with it, even if I had to take it off, because I worked at a swimming pool.” O’Donnell said if she had any advice for future continuous glucose-monitoring systems, they should be less restricting and more accurate. She said if done the right way, these monitors have value. “Having your blood sugar continuously monitored is a really good benefit,” she said. Braun and Zhang said that they are aware that continuous glucose monitoring systems already exist in the commercial market, but their sensor material is different. “Existing products that are on the market now use enzyme electrodes to monitor glucose levels,” said Zhang. Using this method, glucose concentration is correlated with the intensity of electrochemical signals. “Our approach uses a different chemistry to sense glucose,” said Zhang. When the hydrogel material that they constructed comes in contact with glucose, it changes color, ranging on a scale of red to green, said Zhang. For each glucose concentration level, there is a corresponding color, and these colors are identified by their specific wavelength. “Glucose concentration here is correlated with wavelength of light or color of light, which can provide accurate readings. Our approach is also cheap in cost. We offered an alternative design for continuous glucose monitoring, with a potential to meet many critical requirements for clinical use,” said Zhang. The change in the gel’s color happens as the gel material, formally called polyacrylamide, expands. Small particles in the gel called polystyrene particles move apart when the gel expands. As the space between them changes, so does the way the gel manipulates light. This causes the change in the gel’s color. Glucose in the blood stream is attracted to the gel, which contains boronic acid. When glucose floods into the gel from the bloodstream, the gel naturally expands. Braun and Zhang quickly discovered that, in order for their sensor to work, they needed to first add a volumeresetting agent called polyvinyl alcohol into the gel so that it would

Technograph Volume 130, Spring 2015  
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