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article imageHuman stomach acid powers tiny medical sensors

By Tim Sandle     Feb 8, 2017 in Science
Researchers have developed small voltaic cells that are sustained by the acidic fluids in the stomach. The cells are designed to power sensors or as drug delivery vehicles.
The voltaic cells have been designed by scientists from MIT and Brigham and Women's Hospital. Voltaic cells are electrochemical cells that obtain electrical energy from spontaneous reactions taking place within the cell. cells generally consists of two different metals connected by a salt bridge, or individual half-cells separated by a porous membrane. What is remarkable about the new cells is that they are sustained by the acidic fluids in the human stomach.
The researchers have successfully designed the cells in such a way that they can generate enough power in order to run small sensors that can reside in the gastrointestinal tract for extended periods of time. The cells can also be used as vehicles to deliver drugs to specific locations in the body.
Emerging medical devices, such as sensors designed to be ingested so that data about patient health can be collected, are normally battery powered. These can be unreliable since batteries often fail or they are affected by bodily fluids. The new cells were inspired by a common school experiment where a lemon battery is made. Here two electrodes — often a galvanized nail and a copper penny — are stuck into a lemon. The citric acid in the lemon is capable of carrying a small electric current between the two electrodes.
What the researchers came up with was a zinc and copper electrode, linked to the surface of an ingestible sensor. The zinc emits ions into the acid in the stomach to power the voltaic circuit. This, in tests, produced sufficient energy to power a temperature sensor and a 900-megahertz transmitter.
The current prototype of the device is a cylinder about 40 millimeters long and 12 millimeters in diameter. The longer-term aim is to create a new generation of electronic indigestible pills that will enable novels ways of monitoring patient health and, perhaps, for treating disease.
The new devices are described in the journal Nature Biomedical Engineering, with the research study titled "Prolonged energy harvesting for ingestible devices."
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