Editors' ChoiceBiomedical Engineering

Communicating Wirelessly with Our Bodies

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Science Translational Medicine  06 Apr 2011:
Vol. 3, Issue 77, pp. 77ec49
DOI: 10.1126/scitranslmed.3002458

Miniature wearable or implantable medical devices can continuously monitor a patient’s physiological signals in real time—such as heart rhythms, brain activity, and blood glucose levels—and translate these readouts to either automatic, device-based intervention or therapeutic suggestions delivered to a physician. One challenge for these monitoring systems is going wireless: Getting system subunits that are located in or on different parts of the body, or even located externally, to communicate is not a trivial task. Xu and colleagues therefore explored the use of the human body itself as a means of transmitting signals between multiple subunits.

Traditional approaches to wireless communication between biomedical devices reuse technology that has been developed for radios and cell phones. Xu et al. instead used an intra-body communication (IBC) system that uses a natural medium—the human body—to transmit signals. Specifically, the authors studied the electric-field IBC method, in which a closed-loop circuit for signal transmission is formed through capacitive coupling of the conductive human body and the air around the body. First, they used a finite element model to simulate IBC by considering the human body and surrounding space as a collection of hundreds of tiny pieces, or “elements,” with realistic electromagnetic and physiological properties. Next, they tested the electric-field IBC experimentally in a human subject. Signals were emitted from a battery-powered circuit board, and a spectrum analyzer was used as the receiver to measure the magnitudes of received signals at various frequencies, ranging from 1 to 180 MHz. Using the magnitude of transmitted signals as the metric, Xu et al. examined the effectiveness of intra-body communications under various settings—for example, varying the distance between the transmitter and receiver as well as the separation between the ground electrode of the transmitter and the patient's arm. Predictions from the model were able to match data collected from human experiments. This study not only further supports the feasibility of electric-field IBC, but also generated an effective finite element model that will help engineers to better design future IBC systems for wireless medical devices.

R. Xu et al., Electric-field intrabody communication channel modeling with finite-element method. IEEE Trans. Biomed. Eng. 58, 705–712 (2011). [PubMed]

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