Researchers at Stanford University have created a millimeter-sized, wirelessly powered implanted cardiac device. In a feasibility study, they showed how this implanted device contained in a cube just eight-tenths of a millimeter in radius could be powered by radio waves transmitted from outside the body. Although wireless power itself is not completely new, as the new generation of Nikola Tesla fans will tell you, using it to power such a small device five centimeters inside the chest is a great marvel of engineering.
Implantable medical devices such as pacemakers and cochlear implants are increasingly important for patients with a wide variety of medical conditions. One of the main engineering challenges associated with them is powering them. In most cases this is done with batteries, but these are bulky and require replacement after a certain time. Wireless power has the potential to solve both these problems.
Previous mathematical models indicated that low-frequency transmitters and large antennas, too large to be practical for implantable devices, would be necessary for wireless power within the body. The researchers have shown now that high-frequency wireless power transmission to a device in the human body is possible at much deeper depths within the body than previously thought. An important advantage of this is that higher frequency waves can work with smaller coils on the receiving device.
With the new method, optimal power transmission happens at 1.7GHz, at a rate about 10 times more efficiently than earlier devices and with a receive antenna 10 times smaller than previous ones. The images above show power delivery to the human heart from a 200MHz low-frequency transmitter (left) and a 1.7GHz high-frequency transmitter (right), showing focusing of power on the heart in the right image. This way a millimeter-radius coil could harvest over 50 microwatts of power. The researchers think their solution could potentially be used for virtually any medical applications for which device size and power matter, including swallowable pillcams, permanent pacemakers and precision brain stimulators. The findings were published in the journal Applied Physics Letters.
Article in Applied Physics Letters: Wireless power transfer to a cardiac implant…