26 May 2014

Miniature Wireless Heart Rate Driver

It is quite possible that very soon modern heart rate drivers and other medical implants, bulky and in need of batteries, will go down in history. Stanford University researchers have developed a wireless rhythm driver the size of a grain of rice and successfully implanted it in a rabbit. If subsequent experiments bring positive results, tiny and safe medical implants of a new generation will appear on the medical market in 5-10 years.

Modern pacemakers, cochlear implants and other implantable medical devices are powered by batteries that are either built into the implant itself or connected to it by long wires. At the same time, surgical intervention is required to replace the batteries or repair damage to the wires. Recent developments have made it possible to create very small pacemakers that can be delivered and installed in the heart using a catheter inserted into the inguinal artery. However, even such rhythm drivers periodically need to replace batteries.

An alternative approach, first proposed in the 1960s, is to feed implants using radio waves emitted by induction coils located outside the body. Theoretically, this would eliminate the need for surgical interventions to replace batteries, and would also allow to further reduce the size of the device. However, in practice, previously developed prototypes of devices were so inefficient that a transmitter placed on the patient's chest would have to transmit a signal with a power of about 100 watts through the chest. This is more than enough to cause a burn.

In search of a solution to this problem, the authors completely revised the approach to creating transmitters. Using mathematical calculations, they came to the conclusion that the electromagnetic radiation emitted by the optimal transmitter should travel along a certain trajectory and have a frequency approximately corresponding to the frequency at which mobile phones operate. Based on these calculations, the researchers developed a transmitter, which is a 6-centimeter plate with three circular recesses in the shape of tridents. This transmitter operates at a frequency of 1.6 gigahertz and, like earlier versions, is placed on the breast skin directly above the implanted rhythm driver.

After that, the authors tested the effectiveness of the new sensor on simulators of the human heart and brain, in which 2-millimeter rhythm drivers carrying tiny receiving coils were embedded. Experiments have shown that when using the system developed by them, 100 times less energy is required to power the implant than in the case of traditional transmitters based on induction coils.

At the next stage of the study, the rhythm driver was implanted in rabbits and successfully controlled its operation without harm to the animal's skin. Currently, the authors are preparing the developed system for clinical trials.

Experts consider the new development to be very promising, but some express doubts that the replacement of batteries of such transmitters, as well as their placement on the chest, can be trusted by the patients themselves. Alternatively, the transmitter can be implanted under the skin, which will provide an additional level of security.

Article by John S. Ho et al. Wireless power transfer to deep-tissue microimplants is published in the journal Proceedings of the National Academy of Sciences c.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on Stanford University materials:
Stanford engineer invents safe way to transfer energy to medical chips in the body.


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