A small flexible tube equipped with a camera and sometimes with other accessories can be used to examine the inside of the stomach and part of the intestine in detail.
There are some regions of the small intestine that cannot be reached this way, and so swallowable devices have been created to solve this problem. They can do many things, such as take photos, make detections, and even administer drugs. The problem is energy. Until now, the electronics of these devices use primary batteries that have modest energy reserves, so they cannot work for a long time.
Other energy options for examining the small intestine from within are less viable: traditional batteries are potentially harmful, wireless energy transfer from outside the body is inefficient, temperature differences are not sufficient to harness heat energy, and bowel movement is difficult. too slow to gain mechanical power.
The team of Seokheun “Sean” Choi, from Binghamton University (State University of New York) in the United States, has devised a way to overcome all these limitations. His new system is based on the advances made in recent years by Choi and his collaborators in the use of bacteria to generate electrical energy. The energy levels achieved with these unique power supply sources are very low, but they are enough to power small sensors and Wi-Fi connections.
Artist’s rendering of the microbial device capable of powering ingestible chambers in the small intestine. (Image: Sean Choi. CC BY-NC-ND)
Choi’s system uses fuel cells with spore-forming Bacillus subtilis bacteria that remain inert until they reach the small intestine. There, the prevailing conditions cause the fuel cell to activate.
Once the fuel cell reaches the small intestine, it takes up to an hour to fully germinate. It is expected that in future improved versions of the system this waiting time will be considerably reduced. The device generates about 100 microwatts per square centimeter of power density, enough for wireless transmission, though Choi and his colleagues are working on increasing the power to ten times that, which would allow for many more usage options for the device.
Choi’s team discusses the technical details of their innovative system in the academic journal Advanced Energy Materials, under the title “A Biobattery Capsule for Ingestible Electronics in the Small Intestine: Biopower Production from Intestinal Fluids Activated Germination of Exoelectrogenic Bacterial Endospores.” (Fountain: NCYT de Amazings)