Micro/Nano-Fabricated Glucose Sensors
INVENTION: This invention is a novel glucose sensor that uses the hydrogen-specific gas sensing capability of single walled carbon nanotubes (SWCNT’s) assembled on a microelectrode. The conductivity of SWCNT’s changes due to adsorption of hydrogen that causes the energy band structure of SWCNT’s to shift. The invented glucose sensor exploits this phenomenon and demonstrates the following advantages over currently employed techniques:
Highly Sensitive: The invented glucose sensor has been successfully tested at concentration levels as low as one (1) micromole, but in principle the concentration level can be as low as 0.028 micromoles. The invented glucose sensor’s sensitivity can in fact be increased by increasing density of SWCNT’s. In contrast, currently employed techniques demonstrate a low correlation with blood glucose levels. One minimally-invasive glucose sensor that is commercially available was in error 31 percent of the time by at least 30 percent.
Highly Selective: The invented glucose sensor, while highly sensitive to hydrogen, is highly insensitive to non-indicating blood constituents.
Responds Quickly: The invented glucose offers its best results within about 10 seconds of start of test.
Low-cost and compact: Current non-invasive techniques can be bulky and expensive. The invented glucose sensor requires a few thousand carbon nanotubes per device (on the order of 1mm by 1mm in size), and it lends itself to a simple manufacturing process. Only electrical resistance needs to be measured, and the sensor can be easily operated by anyone.
No Calibration: The invented sensor requires no calibration. Current minimally-invasive methods can require frequent finger-pricks for calibration. The invented glucose sensor enables a new kind of product to be offered to the market. That product would be minimally invasive and possibly non-invasive, relying only upon a small sample quantity of blood or other body fluid. It would be highly sensitive, immune to false positives, and would provide results very quickly. The invented glucose sensor would be affordable to manufacture, and is simple and compact. It would NOT require any calibration.
The invented glucose sensor incorporates straightforward lithographic techniques. It has demonstrated a signal-readout that is proportional to glucose levels in a clinically significant range.
State of Development: A prototype has been developed, and initial tests performed. Water droplets with diluted H2O2 have been applied to the sensor and tested. Experimental results for H2 sensitivity and specificity are shown in the figures below. A patent is pending for this invention. See “Microfabricated glucose sensor based on single-walled carbon nanotubes” Chung, Jaehyun; Lee, Kyong-Hoon; Lee, Junghoon Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS), 17th IEEE International Conference on Micro Electro Mechanical Systems (MEMS): Maastricht MEMS 2004 Technical Digest, 2004, p 617-620.
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