Synopsis: Better Signals from Electronic Body Implants

The transmission distance of a wireless implant could be tripled by carefully tuning the frequency of the electromagnetic signal it emits.
Synopsis figure
D. Nikolayev/University of Rennes 1

A medical monitoring device can be implanted in the body to perform functions such as recording brain activity or analyzing blood. The device periodically transmits data wirelessly to a receiver outside the body, but the receiver needs to be within about a meter of the device because of the poor radiation efficiency of biological tissues. Now Denys Nikolayev from the University of Rennes 1, France, and colleagues predict that these transmissions could be made 10 times more efficient by choosing the right frequency. This efficiency increase could enable the transmission distance of these devices to be tripled.

The team modeled the propagation of electromagnetic waves through tissues to find the optimal operating conditions for an implanted device. They considered four geometrical arrangements. The simplest was a uniform slab of muscle with the transmitter embedded some distance below the surface, and the most complicated was a waist-level slice through the human body, complete with fat, stomach, and kidney tissues.

In all cases, the team found that the radiation efficiency of the transmitter improved as they increased the operating frequency up to a few gigahertz, above which the efficiency plummeted. (The exact optimal operating frequency depended on both the implantation depth and the thickness of fat and skin layers.) They also observed that most of the signal’s total energy (80%–99%) was lost at the interface between the body and the air, where the waves reflect back into the body. Attenuation of the signal as it traveled from the implant through the tissues was a much smaller effect.

This research is published in Physical Review Applied.

–Katherine Wright

Katherine Wright is a Contributing Editor for Physics.


More Features »

Subject Areas

Biological PhysicsInterdisciplinary Physics

Previous Synopsis

Semiconductor Physics

Device to Probe Electron-Phonon Interactions

Read More »

Related Articles

Viewpoint: A Toy Model for Active Interfaces
Biological Physics

Viewpoint: A Toy Model for Active Interfaces

A new statistical model predicts the evolving shape of a cellular membrane by accounting for the active feedback between the membrane and attached proteins. Read More »

Viewpoint: The Dance of Water Molecules around Proteins
Biological Physics

Viewpoint: The Dance of Water Molecules around Proteins

A combination of experiments, simulations, and modeling has revealed the anomalous diffusion of water molecules along the surfaces of proteins. Read More »

Focus: Fluid Interactions Help Fish in a School Swim Faster
Fluid Dynamics

Focus: Fluid Interactions Help Fish in a School Swim Faster

Simulations of fish schools that include fluid dynamics in addition to the usual coordination of individuals lead to faster swimmers and reveal a new collective swimming mode. Read More »

More Articles