Wireless energy transfer to the body: the new revolution for implantable medical devices

A team of engineers at Stanford University demonstrated that can transmit high frequency wireless power to a device in the human body. Captured on the energy transfer process to a device implanted in the heart in frequency 200MHz (left) and 1.7 GHz (right). Red represents energy transfer in large, less green. Note the high energy concentration in a small region in the picture to the right. Perhaps the upcoming year will be the year of wireless charging. Irrelevant to Qi or smartphone technology wireless rechargeable Nokia Lumia 920 has just introduced recently, a group of engineers at Stanford University (USA) have demonstrated the ability to transmit wireless energy by radio waves from outside the medical device into a very small radius of about 0.8 mm in heart transplant patients. According to the study, the depth of penetration of wireless power can be up to 5cm below the chest muscle.   Published in the journal Applied Physics Letters by Ada Poon, a professor of electrical engineering at Stanford, along with two of his graduate students, research promises to open up a new direction in energy supply for devices implanted in the body with health advantages compared to the traditional methods used batteries in terms of device size, simple, and convenient. The team believes that the application of the devices may include devices can swallow endoscopy (PillCam), the cardiac pacemaker (pacemaker) lifetime activity, or brain stimulation (Brain Stimulator).   Revolution of the implantable medical device Medical devices implanted in the human body has revolutionized medicine. Hundreds of thousands of heart pacemaker, millions of medical devices placed in the cochlea, or a lot of drug pumps implanted (implantable drug pump) are hourly help people live a normal life. However, the generation of medical devices now have some inherent disadvantages are difficult to change.   An energy equipment required to operate and batteries often perform that task. Do you know of a device such as a pacemaker battery, own up to half the size of the device. Large size is one of the disadvantages of generations of implanted medical devices today with the battery is the main cause. In addition, the limited amount of energy that we can only offer surgery causes a per-device implanted battery. It was a nightmare.   "Wireless Energy solves two challenges,", Ada Poon said. And power supply for implantable medical devices via the wireless communication will make the next revolution in this field.   Principle of operation of the new equipment Poon latest device works by combining the method of energy transfer by radiation and induction. A radio transmitter sends a signal to a coil in the human body which produces an electric current in the wire enough to provide for equipment operation.   These difficulties were overcome Last year, Poon has surprised everyone when she shows that a self-propelled device operation by wireless energy can swim in blood. To do that, there has to be overcome before this hypothesis about the possibility of putting energy into the human body through high-frequency wireless signal.   In physics, there is an indirect relationship between the frequency of the radio waves transmitted and the size of the receiving antenna. Specifically, for a given energy, the lower the frequency the antenna coil must be larger, and vice versa. Therefore, only the wireless energy transfer in the form of high-frequency signals can solve the problem size of the implant.   However, many mathematical models of current at Poon real time current research suggests that high-frequency radio waves can penetrate far enough through the body tissues. Poon prove that the model is wrong completely. According to Poon, the size of the scattered electric field is very fast, this is true, but radio waves can propagate in a different way: the rotating waves of electrical and magnetic fields. With the right mathematical equation theory in hand, Poon found that high-frequency radio waves can penetrate deeper than what people previously thought. According to the revised model of her and her group, the maximum energy can be transmitted through the tissue occurs at the frequency of 1.7 GHz.   "In this high-frequency region, we can increase the transmit power by about 10 times compared with the previous generation devices," said John Ho, one of two graduate students in the group, said. This means that at this frequency, a coil of radius size 1mm able to obtain more than 50 microwatt power, more than enough to run a heart pacemaker (just about the 8 microwatt only).   Job ... and the future Despite solve most of the problems, however, the research team said the next time they have to overcome a number of difficulties related to the fabrication process. First, the group of medical devices must comply with stringent health standards issued by the Institute of Electrical and Electronics Engineers (IEEE - Institute of Electrical and Electronics Technology), especially tissue heating problems can. Second, the group must seek and receive antenna orientation that optimizes transmission performance, because previous studies showed that only a few degrees difference, have greatly reduced transmission performance, which this shall not be allowed to happen with a medical device.   Currently, the research team says it has designed a kind of new type of TV antenna can avoid this problem. Accordingly, the new design will focus radio waves exactly at a point inside the body where the device fixed on the surface of the heart. Specifically, it will increase the electric field at the place most in need while suppress them in other places This will help reduce the level of heat the lower limit allowed by the IEEE standard.   With momentum this study, we can fully expect the implantable medical device is energized through wireless communication will appear on the market in one day and then the patient will not longer have to be afraid of in the depleted batteries anymore or they are too big to put into our subtle body.   Detailed interest you can download the article in the journal Applied Physics Letters website here.   Professor Ada Poon:      Source: Stanford ...