Researchers at Stanford University have developed a new way to safely transfer energy to tiny medical devices implanted deep inside the human body. The advance could lead to the development of tiny "electroceutical" devices that can be implanted near nerve bundles, heart or brain tissue and stimulate them directly when needed, treating diseases using electronics rather than drugs.
Electromagnetic waves can be roughly divided in two: far-field waves, which can travel long distances, but interact weakly with the human body; and near-field waves, which can be used in wireless electronics systems, but can only transfer power over very short distances and are severely refracted when they encounter human tissue. Those characteristics make it difficult to use either of them to power medical implants inside the body.
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A team led by Stanford assistant professor Ada Poon combined the best of those two worlds by developing a power source that generates a near-field wave that is harmless to humans and is also able to effectively penetrate tissue to charge small electronic implants inside a patient.
Batteries are by far the largest, bulkiest component of today's medical implants, and their size is limiting the scope of application. Using this new technology, medical implants could run on significantly smaller batteries, shrinking down to the size of a grain of rice, and be implanted much deeper within the body, where they could be charged safely from the outside and open up a wide range of new applications.
The power source is a small device the size of a credit card. When the electromagnetic waves that it generates move from air to the patient's skin, they refract in such a way that they are able to propagate safely and effectively through human tissue, in what the researchers call a "mid-field wireless transfer."
This technology could pave the way to a new generation of highly convenient pacemakers and other micro-implants that could do anything from constantly monitoring vitals to generating neural signals when needed inside the brain, for instance to fight diseases such as Parkinson's, depression and epilepsy. Their smaller size would also make the surgery itself much safer and less invasive.
Poon and colleagues are planning to begin testing their device in humans in the near future, starting a process that will likely take a few years.
The research appears in the latest issue of the journal Proceedings of the National Academy of Sciences.
In the video below, the researchers explain how their technology could be applied to future medical devices.