Engineers Harness Stomach Acid to Power Tiny Sensors
February 7, 2017 | MITEstimated reading time: 4 minutes
Researchers at MIT and Brigham and Women’s Hospital have designed and demonstrated a small voltaic cell that is sustained by the acidic fluids in the stomach. The system can generate enough power to run small sensors or drug delivery devices that can reside in the gastrointestinal tract for extended periods of time.
This type of power could offer a safer and lower-cost alternative to the traditional batteries now used to power such devices, the researchers say.
“We need to come up with ways to power these ingestible systems for a long time,” says Giovanni Traverso, a research affiliate at the Koch Institute for Integrative Cancer Research. “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.”
Traverso, who is also a gastroenterologist and biomedical engineer at Brigham and Women’s Hospital, is one of the senior authors of the study. The others are Robert Langer, the David H. Koch Institute Professor at MIT; and Anantha Chandrakasan, head of MIT’s Department of Electrical Engineering and Computer Science and the Vannevar Bush Professor of Electrical Engineering and Computer Science. MIT postdoc Phillip Nadeau is the lead author of the paper, which appears in the Feb. 6 issue of Nature Biomedical Engineering.
Sustained by acid
Traverso and Langer have previously built and tested many ingestible devices that can be used to sense physiological conditions such as temperature, heart rate, and breathing rate, or to deliver drugs to treat diseases such as malaria.
“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,” Langer says.
These devices are usually powered by small batteries, but conventional batteries self-discharge over time and pose a possible safety risk. To overcome those disadvantages, Langer and Traverso worked with Nadeau and Chandrakasan, who specialize in developing low-power electronics.
The research team took inspiration from a very simple type of voltaic cell known as a lemon battery, which consists of two electrodes — often a galvanized nail and a copper penny — stuck in a lemon. The citric acid in the lemon carries a small electric current between the two electrodes.
To replicate that strategy, the researchers attached zinc and copper electrodes to the surface of their ingestible sensor. The zinc emits ions into the acid in the stomach to power the voltaic circuit, generating enough energy to power a commercial temperature sensor and a 900-megahertz transmitter.
In tests in pigs, the devices took an average of six days to travel through the digestive tract. While in the stomach, the voltaic cell produced enough energy to power a temperature sensor and to wirelessly transmit the data to a base station located 2 meters away, with a signal sent every 12 seconds.
Once the device moved into the small intestine, which is less acidic than the stomach, the cell generated only about 1/100 of what it produced in the stomach. “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,” Traverso says.
“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,” says John Rogers, a professor of materials science and engineering at Northwestern University, who was not involved in the research. “These types of systems have great potential to address important clinical needs.”
Miniaturization
The current prototype of the device is a cylinder about 40 millimeters long and 12 millimeters in diameter, but the researchers anticipate that they could make the capsule about one-third that size by building a customized integrated circuit that would carry the energy harvester, transmitter, and a small microprocessor.
“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,” Chandrakasan says.
Once the researchers miniaturize the device, they anticipate adding other types of sensors and developing it for applications such as long-term monitoring of vital signs.
“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 says.
Such devices could also be used for drug delivery. In this study, the researchers demonstrated that they could use the power generated by the voltaic cell to release drugs encapsulated by a gold film. This could be useful for situations in which doctors need to try out different dosages of a drug, such as medication for controlling blood pressure.
The research was funded by Texas Instruments, the Semiconductor Research Corporation’s Center of Excellence for Energy Efficient Electronics, the Hong Kong Innovation and Technology Commission, the National Institutes of Health, and the Max Planck Research Award.
Suggested Items
Insulectro’s 'Storekeepers' Extend Their Welcome to Technology Village at IPC APEX EXPO
04/03/2024 | InsulectroInsulectro, the largest distributor of materials for use in the manufacture of PCBs and printed electronics, welcomes attendees to its TECHNOLOGY VILLAGE during this year’s IPC APEX EXPO at the Anaheim Convention Center, April 9-11, 2024.
ENNOVI Introduces a New Flexible Circuit Production Process for Low Voltage Connectivity in EV Battery Cell Contacting Systems
04/03/2024 | PRNewswireENNOVI, a mobility electrification solutions partner, introduces a more advanced and sustainable way of producing flexible circuits for low voltage signals in electric vehicle (EV) battery cell contacting systems.
Heavy Copper PCBs: Bridging the Gap Between Design and Fabrication, Part 1
04/01/2024 | Yash Sutariya, Saturn Electronics ServicesThey call me Sparky. This is due to my talent for getting shocked by a variety of voltages and because I cannot seem to keep my hands out of power control cabinets. While I do not have the time to throw the knife switch to the off position, that doesn’t stop me from sticking screwdrivers into the fuse boxes. In all honesty, I’m lucky to be alive. Fortunately, I also have a talent for building high-voltage heavy copper circuit boards. Since this is where I spend most of my time, I can guide you through some potential design for manufacturability (DFM) hazards you may encounter with heavy copper design.
Trouble in Your Tank: Supporting IC Substrates and Advanced Packaging, Part 5
03/19/2024 | Michael Carano -- Column: Trouble in Your TankDirect metallization systems based on conductive graphite or carbon dispersion are quickly gaining acceptance worldwide. Indeed, the environmental and productivity gains one can achieve with these processes are outstanding. In today’s highly competitive and litigious environment, direct metallization reduces costs associated with compliance, waste treatment, and legal issues related to chemical exposure. What makes these processes leaders in the direct metallization space?
AT&S Shines with Purest Copper on World Recycling Day
03/18/2024 | AT&SThe Styrian microelectronics specialist AT&S is taking World Recycling Day as an opportunity to review the progress that has been made in recent months at its sites around the world in terms of the efficient use of resources: