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Wireless technology is expected to expand significantly into medical areas for a number of different applications. These include remote monitoring of patients, fast access of medical data for medical professionals, and tracking dementia patients by means of Global-Positioning-System (GPS) devices. Combining wireless communications with the growing number of sensors used for health applications—such as for monitoring heart rate, blood oxygen levels, and blood sugar levels—makes it possible for a doctor to remotely check on a patient and even trigger a medical response from a distance if necessary.

Some of the growing number of wireless solutions for healthcare applications are expected to fall under the category of “machine-to-machine” (M2M) applications. These are applications in which remote sensors may be communicating via the Internet and with wireless technologies with automated monitoring stations, alerting a medical professional when some action must be taken.

Research being performed as part of the WISERBAN project seeks to improve the state of electronic body implants (such as pacemakers) with improved communications capabilities, lower power consumption, and reduced size. The project is focused on the miniaturization of wireless body-area-network (WBAN) devices, applying a number of different technologies, including RF/microwave and microelectromechanical-systems (MEMS) devices. So far, the organization has succeeded in combining these technologies into the fabrication of a low-power radio measuring just 4 x 4 x 1 mm. It combines MEMS and CMOS integrated-circuit (IC) technologies to save size and power.

In the United States, the Federal Communications Commission (FCC) has already set aside spectrum in the band from 2.36 to 2.40 GHz for the use of WBAN devices. By employing such devices in hospitals, clinics, and doctors’ offices, the hope is to eliminate the clutter of cables currently used to operate electronic devices for patient monitoring, as well as to improve the efficiency of communications among the different electronic medical devices.

For their part, WISERBAN, in addition to refining software in support of these WBAN devices, has developed system-on-chip (SoC) devices that integrate MEMS devices, radio circuitry, and digital-signal-processing (DSP) circuitry on a single silicon die. WISERBAN has also tackled an important component of any medical wireless solution—the antenna—and created miniature antenna prototypes capable of covering the entire 2.4-GHz frequency band. The organization has also developed and optimized a dedicated protocol stack for low-power communication with body-sensor networks. The WISERBAN project is coordinated by the Centre Suisse d’Electronique et de Microtechnique (CSEM) in Neuchatel, Switzerland.

Stanford University has also been active in researching emerging wireless technologies for healthcare applications. Stanford Assistant Professor Ada Poon has developed self-propelled, wirelessly powered medical devices capable of controlled motion through blood and other bodily fluids. The medical devices can be implanted or injected into the human body and powered wirelessly, by means of an applied electromagnetic (EM) field. These devices could potentially be used to travel through the bloodstream to deliver drugs, provide analyses, remove plaque from arteries, and even perform minimally invasive surgeries.

2. Implantable in-body medical devices draw power from external EM fields operating at about 1 GHz. (Photo courtesy of Stanford University.)

Implantable medical devices have traditionally been challenged by their need for power, from batteries, which limited how small the devices could be made. These new devices draw power from an EM field and can be made extremely small without batteries (Fig. 2). Poon’s work required a rethinking of how human tissue responds to EM energy, with her modeling tissue as a low-loss dielectric material. She was able to use a higher frequency, at 1 GHz, for powering the implanted devices, and use smaller antennas for those devices. Research on these tiny medical devices was made possible by the support of C2S2 Focus Center, Olympus Corp., and Taiwan Semiconductor Manufacturing Co. (TSMC).

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