Stanford scientists have developed a pacemaker-like medical device the size of a grain of rice that can be powered wirelessly, negating the need for bulky batteries that have represented a major hurdle in the medical implant field. The device can be implanted deep into tissues and is capable of delivering electrical pulses to virtually anywhere in the body. It is hoped that eventually, these “electroceutical” devices could be used to treat disease or relieve pain without drugs. The study has been published in the Proceedings of the National Academy of Sciences of the United States of America.
Scientists have made significant progress over the years in the development of medical implants that can interact with organ systems and enhance or replace certain physiological functions. The devices need to be small, however, the substantial amount of energy required to power the devices has made downsizing difficult as bulky batteries are often necessary. An alternative method is to use wireless transfer of electromagnetic waves from external sources, which is what this team of Stanford scientists, led by assistant professor of engineering Ada Poon, turned to.
Electromagnetic waves are utilized in a wide variety of technologies, from microwave ovens to radio transmission. Broadly, the ones that we use are classified into two distinct types; far-field and near-field. Far-field waves, as the name suggests, are capable of traveling long distances, but they’re generally reflected off of skin or absorbed as heat so are not useful in this scenario. Near-field waves transfer power over short distances and while they have been useful in devices such as hearing aids, they are far from ideal for use in reaching tissues deep within the body.
Since neither of these waves are suitable for powering deep tissue implants Poon set out to develop a compromise between the two, marrying the reach of far-field waves with the safety of near-field waves. To do this, she turned to the electromagnetic midfield and generated a power source that can wirelessly transfer a special type of near-field wave that is capable of both traveling through air and propagating through tissue.
“With this method, we can safely transmit power to tiny implants in organs like the heart or brain, well beyond the range of current near-field systems,” said co-lead author John Ho in a news-release.
Poon and colleagues used this so-called mid-field wireless transfer system to power tiny medical implants by holding an external power source around the size of a credit card above the device. Independent laboratory tests found that the wireless system fell well below exposure levels considered dangerous for humans. Poon’s team were also able to power a pacemaker in a rabbit using this wireless system. The team hope to be able to move forward and initiate human trials soon to investigate safety and efficacy, although if successful it will still be many years before this system is commercially available.
According to Poon, this system could pave the way for the development of a novel generation of medical implants with diverse functions, from monitoring organ functions to drug delivery systems that target therapies to specific areas of the body.
This research has sparked interest in many, including Stanford neuroscientist William Newsome. According to Newsome, who was not involved in the work, these “electroceutical” treatments could be particularly useful in treating some neurological disorders because they could directly modulate specific brain circuits. This system would be an attractive alternative to drugs that act globally across the brain, rather than targeting precise areas like these implants could.
If you’d like to know more, check out this YouTube video released by Stanford.