Ingestible Electronics Update: MIT and Stanford’s Midfield Transmission

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ingestible electronics
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A research team from three different institutions joined forces to devise a technique to wirelessly power ingestible electronics, which could then remain inside the body indefinitely.

We have recently covered five of the latest breakthroughs in drug delivery systems. However promising and beneficial, all these medical devices need a source of power to operate. Which, from inside the body, finding power is easier said than done. Often outfitted with a battery, these electronics can only work for limited periods of time.

An MIT research team, via multiple joint initiatives, has been working on new ways to power millimeter-sized ingestible electronics.

1. Electrode-Based Battery Cell

One of the various approaches explored was a system that generates power the same way as a “lemon battery”; a galvanic cell that harvests power from acid in the gastric tract.

But this battery cell suffers from a major setback: the two tiny metal electrodes fail over time, the chemical reaction stops and the whole system shuts down.

2. Near-Field Transmission

The team wanted to find a way to power ingestible electronics without the need for metal electrodes and make them last indefinitely in the GI tract.

So, researchers considered using “near-field transmission,” or the approach used in some cellphone chargers. In other words, transferring power wirelessly between two antennas; but because the antennas must be very close to each other, researchers deemed this approach presently too limited for their purposes, as they need to cover a distance (between antennas) of 5 to 10 centimeters.

3. Midfield Transmission

Recently, researchers at Stanford University have explored “midfield transmission” to power implantable pacemakers. The MIT team built on that and tried this approach, which enables a broader range of wireless power transfer for their ingestible devices.

In a new collaboration with Brigham and Women’s Hospital (after the galvanic cell), MIT researchers seem to finally have found the ultimate alternative to batteries for gastrointestinal electronics.

Using midfield transmission, the team delivered (from one antenna to the other) 100 to 200 microwatts of power to their GI device, more than enough for small electronics, such as temperature sensor that require only 30 microwatts to function and send readings every ten seconds. Tests in pigs showed the external antenna could transfer power over 2 to 10 centimeters to the internal antenna (in the device inside the GI tract), and, more importantly, the energy transfer caused no tissue damage.

An article on the research–which was funded by National Institutes of Health and by a Draper Fellowship–was published in Scientific Reports journal.

The team hopes that human tests will be run within the next 5 years.

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