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Diagnostic Kit Powered by Just a Drop

Originally Published MDDI November 2005 R&D Digest Diagnostic Kit Powered by Just a Drop Heather Thompson

Originally Published MDDI November 2005

R&D Digest

Diagnostic Kit Powered by Just a Drop

Heather Thompson

The biofluid battery is powered by the sample fluid being tested.

Using the same biofluid sample undergoing testing, a diagnostic kit powers its own battery. The kit is small—about the size of a credit card—disposable, and designed for clinical or home use.

The kit integrates various chemical and biological processes onto a laminated plastic platform with a self-activated power source. A drop of biofluid such as blood or urine on the integrated battery generates enough electricity to power the device, enabling the latter to analyze the biofluid sample for specific disease biomarkers. Ki Bang Lee, PhD, principal research scientist with the Institute of Bioengineering and Nanotechnology (IBN) in Singapore created the kit. In 2004, Lee noticed the power sources of most diagnostic kits were too bulky and so limited the kits' use. “The challenge is to produce an inexpensive battery that can be fabricated on a biochip. Using the urine-activated battery, we do not need an external power source. We can simply integrate the battery and biosensors on a plastic chip.”

Lee explains that the device works very simply. The urine-activated battery consists of an upper layer of magnesium, a layer of copper chloride– doped paper, and a lower layer of copper. These layers are sandwiched between a laminated plastic film. When one droplet of urine, about 0.2 ml, is placed on the magnesium layer, and copper chloride– doped paper, and copper layer, the capillary force drives the urine into the paper, and the battery is activated. Magnesium and copper chloride are used as the anode and the cathode, respectively. The copper layer acts as an electron-collecting layer.

Ki Bang Lee created the kit for office or home use.

The resulting battery is just 1 mm thick and 60 ¥ 30 mm across. It generates 1.5 V, with a corresponding current of 1.5 µW. Lee adds that the voltage, current, and capacity of the battery could be improved by different designs or by switching to other electrode or electrolyte materials. And if a second droplet of urine were added 15 hours after the battery was first activated, the replenished urine could generate still more electricity.

According to Lee, the battery can be easily integrated to supply electricity to healthcare test kits. “We can make a credit card–sized biochip by integrating the battery and biosensors for disease detection. When the biochip comes into contact with the biofluid, the battery is activated to supply electricity to the biosensors and a display,” he says.

Although fabricating the kit is relatively simple, Lee says it will take about two more years to bring the kit to market. He is willing, he says, to collaborate with universities, institutes, or companies to further develop the technology. Lee owns the worldwide patent.

Additionally, Lee says he is working at IBN to develop batteries that are powered by the glucose present in the bloodstream and in the urine of diabetic patients. Glucose-activated batteries can be integrated into test kits for the diagnosis of diabetes and to test other critical bodily functions.

Copyright ©2005 Medical Device & Diagnostic Industry

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