A Japanese research group developed a technology to wirelessly transmit data from deep inside a human body to the outside by using a high-frequency weak current.
The group is headed by Kenji Shiba, associate professor at the Department of Applied Electronics at the Tokyo University of Science. The technology is expected to be used for transmitting data collected by an embedded artificial organ or capsule endoscope inside a human body to the outside.
The group plans to launch a research project in collaboration with a device manufacturer in 2014 in the aim of promoting the miniaturization and digitization of communication module.
The new technology transmits a weak current in human body tissues by attaching two electrodes to the embedded device and body surface and utilizing capacity coupling between the electrodes in and outside the body. When an alternating voltage is applied between the two electrodes of the embedded device, the voltage between the two electrodes on the body surface changes. By detecting the voltage change outside the body, it becomes possible to receive data from the embedded device.
Because part of the embedded device can be used as transmission electrodes, there is no need to secure a space for a transmission antenna, making it easy to reduce device size.
The research group prototyped a communication device equipped with 10 x 8mm transmission electrodes and transmitted data from the device to 20 x 20mm reception electrodes via a solution of salt simulating a living body. It transmitted data by using carrier waves with a frequency of 600kHz and frequency modulation.
In the experiment, the group confirmed that data can be transmitted only when the device is in the solution and that it cannot be transmitted in the air because currents cannot be transmitted in the air. This means that it is easy to secure confidentiality, which is required for data transmission from medical devices.
With an output voltage of about 58mV, the density of the weak current being transmitted in human body tissues is 0.12mA/cm2, which is much lower than the safe limit for living bodies (0.6mA/cm2). Also, the power consumption is as low as 9.4μW.
The research group plans to make efforts to commercialize the new technology through the joint research with the device manufacturer and launch another research in the aim of combining the technology with wireless power transmission technologies to power the embedded device and transmit data from it without using a battery.