Sensors and other devices such as pacemakers are designed to be implanted into the human body. These items need a power source, and one of the most common approaches is to include a lithium ion battery. This is well-proven technology, and can have a useful life of up to five years. The problem is that five years is not much time for patients dealing with a chronic condition, and the procedures required to replace depleted battery introduce new opportunities for unwanted complications.
Researchers have been working to develop power sources that run on energy supplied by the patient’s body. Glucose biofuel fuel cells (GBFC) are one approach; it “burns” the glucose available in the blood and other body fluids to power the device. These fuel cells are sensitive to other chemicals in the body, however, which can shorten their useful lifespan. Also there have been biocompatibility problems with other designs, resulting in inflammation around the implant.
French researchers at the University of Grenoble may have come up with a solution. They have built GFBCs that combine carbon nanotubes (CNT) and genipen (derived from gardenia fruits) with chitosan (a natural polymer found in shrimp shells.) The fibrous, 3D structure allows good contact with body fluids in a very small space. It also naturally reduces inflammation so that the implant is tolerated better. The researchers implanted these devices in rats, and found that the host tissues soon grew into the device. These fuel cells were still producing power after six months.
This technology could lead to “self-powered” implants for sensors, micro-mechanical devices, and wireless transceivers. These could open up a host of new applications ranging from medical monitoring and treatment to digital identity and security.