Tiny sensor running on stomach fluid enables new possibilities for data tracking

Credit: MIT.

A new device from US researchers is offering new possibilities for gastrointestinal sensors and medication delivery apparatuses. It is powered by stomach acid, functioning similar to a conventional battery.

Conventional in-stomach sensors rely on battery power which is not as optimal as the new device. The new device can reside in the patient for a longer period of time and is more compact and reliable. Furthermore, it is safer since there is no need for its own power source, and it can remain in the patient for a longer period of time (tests with pig subjects remained in the animal for a mean time of 6 days). Conventional devices can in some cases self-discharge, which poses a risk to safety.

Even after it leaves the stomach to the intestines it generates energy still (99% less than in the stomach but still useful amounts); “But there’s still power there, which you could harvest over a longer period of time and use to transmit less frequent packets of information,” one of the researchers said. 5 wireless data transfers per minute from the device to a base station within a range of 16ft are possible when the device is in the stomach, while much less frequent data transfers would be possible when it is in the intestine.

Such a device could have a number of uses. The main use currently possible is that of timed drug release; the researchers have shown that they can use the energy generated by the device to release drugs contained in gold film based on biometric readings. This would allow trialling of different dosages and release timings.

Langer and Traverso had previously collaborated on similar devices. These include devices to release malaria drugs. As well as this, other ingestible devices they have developed can monitor biometric data such as respiration, body heat, and pulse. Chandrakasan and Nadeau have specialised in creating devices that run on low-energy sources.

Nadeau said of the functionality; “You could have a self-powered pill that would monitor your vital signs from inside for a couple of weeks, and you don’t even have to think about it. It just sits there making measurements and transmitting them to your phone.”

According to Langer: “This work could lead to a new generation of electronic ingestible pills that could someday enable novel ways of monitoring patient health and/or treating disease.”

Even more uses will be possible after the researchers have been able to complete the miniaturisation of the device. Addition of a processor, energy generator and transmission component will be possible when the device is reduced by 66% of its current prototype size. This will enable addition of longer term biometric readings. The device is currently 4cm in length and has a diameter of 1.2cm.

“A big challenge in implantable medical devices involves managing energy generation, conversion, storage, and utilization. This work allows us to envision new medical devices where the body itself contributes to energy generation enabling a fully self-sustaining system,” according to Chandrakasan.

The basic functioning of the device is similar to homemade and science class energy cells, where a source of acid is connected with two different metals to generate an electric charge between them. The two metals used in the device are copper and zinc. Electrical charges are sent from the acid in the stomach through the circuit, generating energy. The resulting charge is enough for the functioning of a thermometer and a 900mhz transmitter.

Another expert not involved in the study, John Rogers of Northwestern University (professor of materials science and engineering) said this of the research: “This paper reports an exciting and remarkably broad collection of advances in ‘ingestible’ electronics — from bioresorbable power supplies to energy efficient electronics, advanced sensors/actuators, and wireless communication systems. These types of systems have great potential to address important clinical needs.”

“We need to come up with ways to power these ingestible systems for a long time. We see the GI tract as providing a really unique opportunity to house new systems for drug delivery and sensing, and fundamental to these systems is how they are powered,” said Traverso.

More information can be found at: MIT

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