Sensors You Can Swallow Could Be Made of Nutrients and Powered by Stomach Acid

Silicon for the smarts, but stomach acid for the power

2 min read
Sensors You Can Swallow Could Be Made of Nutrients and Powered by Stomach Acid
Illustration: Bettinger Group/CMU

The future of ingestible sensors could be a cross between silicon-based circuitry and biodegradable materials, with batteries made of nutrients and running on stomach juices.

That, at least, is the vision of Christopher Bettinger, assistant professor of materials science and biomedical engineering at Carnegie Mellon University. His group is working on edible electronics and ways to power them. Ingestible sensors could provide a gut check for early signs on bacterial infection, look for symptoms of gastrointestinal disorders such as Crohn’s Disease, monitor uptake of medications, and even study the microbiome living inside people.

“I think a lot of people hand-wave powering these devices through external RF, but bodies are a pretty good Faraday cage

Some ingestible sensors, such as a clear pill containing a camera to examine the GI tracts up close, already exist, but they carry a risk of getting stuck and requiring surgery to remove. And researchers are working on devices made from biocompatible materials such as gelatin and indigo. Bettinger thinks the trick is to make the logic circuits out of silicon, taking advantage of the sophistication of that technology, but to encapsulate them in, say, a biodegradable hydrogel that can squeeze through tight openings. The other parts, such as antennas and batteries, would be made from organic and other bio-safe materials.

“If you really want to use these in a clinical setting, we think silicon is pretty good,” says Bettinger, who authored a review article on next-generation devices in the latest issue of Trends in Biotechnology.

One of the main issues is how to supply the sensors with power. “I think a lot of people hand-wave powering these devices through external RF,” he says, “but bodies are a pretty good Faraday cage,” which would prevent radio frequency energy from reaching the sensors. His team has built a battery with a cathode made of melanin—the pigment that colors hair and skin—and an anode made of manganese oxide, a form of a mineral that plays a role in nerve function. The battery has an open design, so that when it hits the stomach, gastrointestinal fluids act as the electrolyte and transport current, much the way the emergency lights of life vests light up when they’re dropped in ocean water. In lab tests, it provided 5 milliwatts of power for up to 20 hours. 

Various minerals, such as manganese, magnesium, and copper are considered essential nutrients, and could be used to build electronics in amounts smaller than the U.S. Food and Drug Administration “Recommended Daily Allowance”, which should help convince that agency of their safety, Bettinger says. “We think we can go to FDA and say, ‘here’s a battery compound of things that are already in our bodies, plus water,’” he explains. Even silicon, if it interacts with the body, can turn into silicic acid, which has some health benefits.

As for the melanin, Bettinger says, “there’s already more melanin in a serving of squid-ink pasta than will be in our batteries.”

The vision of edible electronics may not be far in the future. Proteus Digital Health, of Redwood Shores, Calif., already makes an ingestible sensor that sends data to a patch worn on the skin. Earlier this month they and Otsuka Pharmaceutical, of Tokyo, Japan, filed an application with the FDA for the first combination of a drug with a smart pill. Then hope to sell a pill of Abilify, a drug for mental disorders, with the Proteus sensor embedded within it to monitor drug uptake.

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This CAD Program Can Design New Organisms

Genetic engineers have a powerful new tool to write and edit DNA code

11 min read
A photo showing machinery in a lab

Foundries such as the Edinburgh Genome Foundry assemble fragments of synthetic DNA and send them to labs for testing in cells.

Edinburgh Genome Foundry, University of Edinburgh

In the next decade, medical science may finally advance cures for some of the most complex diseases that plague humanity. Many diseases are caused by mutations in the human genome, which can either be inherited from our parents (such as in cystic fibrosis), or acquired during life, such as most types of cancer. For some of these conditions, medical researchers have identified the exact mutations that lead to disease; but in many more, they're still seeking answers. And without understanding the cause of a problem, it's pretty tough to find a cure.

We believe that a key enabling technology in this quest is a computer-aided design (CAD) program for genome editing, which our organization is launching this week at the Genome Project-write (GP-write) conference.

With this CAD program, medical researchers will be able to quickly design hundreds of different genomes with any combination of mutations and send the genetic code to a company that manufactures strings of DNA. Those fragments of synthesized DNA can then be sent to a foundry for assembly, and finally to a lab where the designed genomes can be tested in cells. Based on how the cells grow, researchers can use the CAD program to iterate with a new batch of redesigned genomes, sharing data for collaborative efforts. Enabling fast redesign of thousands of variants can only be achieved through automation; at that scale, researchers just might identify the combinations of mutations that are causing genetic diseases. This is the first critical R&D step toward finding cures.

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