Ingestible Medical Devices Powered by Gastric Fluids

Scientists have been attempting to produce practical ingestible electronics for years, and now researchers at MIT and Brigham and Women’s Hospital, may have figured out how to power them using surrounding fluids in the gut. Previously developed ingestible electronics typically use batteries that contain materials that, if leaked, are toxic to the human body. Other techniques, such as harvesting heat or vibrations from the surroundings, have been attempted. However, most of these methods don’t produce enough consistent energy to power the sensors in the devices. Giovanni Traverso, the senior author of the study, worked with Robert Langer, a professor at the David H. Koch Institute and Anantha Chandrakasan, head of MIT’s Department of Electrical Engineering and Computer Science, to develop a power source that circumvented these problems. This novel method of providing energy to ingested devices is essentially a voltaic cell. A voltaic cell utilizes two electrodes and an acid to stimulate the flow of electrons to produce a small electric current. To replicate this, the researchers incorporated zinc and copper electrodes on the surface of their sensor. Once ingested, the stomach acid acts as an electrolyte and facilitates the releases of ions from the zinc anode to the copper cathode. The voltaic cell produces .23 microwatts per square millimeter of anode. In their experiments, the researchers found this method produced enough electricity to energize commercial temperature sensors and a 900-megahertz transmitter for an average of six days in live pigs. In additional experiments, the researchers showed that a capsule equipped with this novel system could be used to electrically corrode a gold membrane to release drugs. Currently, the device is 40 millimeters long and 12 millimeters in diameter, but researchers believe that by using customized integrated circuits which would carry the voltaic cell, transmitter, and microprocessor, the device could become considerably smaller. “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,” Nadeau said in a published statement. Recently, Traverso and Langer have also developed a star-shaped drug delivery device that can reside in the gut for weeks. The device remains in the stomach, using its unique shape to prevent it from traveling into the intestines, while still letting food particulates and fluids flow freely. This device, and others like it, are currently powered by batteries, however the potential to power them with the new method is very real and seemingly very near. Study in Nature Biomedical Engineering: Prolonged energy harvesting for ingestible devices…