When it comes to everyday health monitoring, nearly all the information we gather comes from "outside" the body: thermometers, blood tests, stool tests, and the like. Our "inner" body, including core temperature, gut conditions, and microbiome, is something most of us cannot track on a daily basis without a special medical examination.
But what if swallowing a single pill could give you real-time information about the state of your digestive tract, your gut environment, and even the balance of bacteria living inside you?
That is exactly the future health-monitoring challenge being taken on by the Moonshot R&D Program Goal 1 ARAI Project: "Structuring Spatiotemporal Environmental Information in the Body Using In-body Cybernetic Avatars."
Monitoring the body by "swallowing a semiconductor chip - digital pill," is an innovative technology that could completely transform what we know about medicine and health management. We spoke with Kiichi Niitsu of Kyoto University, who is working to develop the world's first "digital pill capable of monitoring the gut environment," to hear about the cutting edge of this research. Why don't we open this new scientific door to understanding the "inside" of our own bodies together?
A press release titled "Development of a Stomach-Acid-Charged Semiconductor Integrated Circuit for a Digital Pill with Gut Environment Monitoring Capability" was issued on October 28, 2025. It's a striking title, but what exactly is a "digital pill"?
Niitsu: Simply put, a "digital pill" is a "swallowable sensor": a conventional tablet with an ultra-compact electronic circuit (semiconductor chip) inside, capable of measuring information within the body and transmitting it to the outside. In-body sensors such as capsule endoscopes already exist, but are large and expensive, making everyday use impractical. What we have developed is a technology that integrates an ultra-compact semiconductor chip into a tablet-style pill, the kind you can easily swallow every day, that generates and stores power from stomach acid without a battery. It can monitor not only the stomach but also the gut environment, including temperature and pH at various locations in the small and large intestine.
So, the pill contains a semiconductor chip! But "swallowing a semiconductor chip" sounds a bit daunting. What about safety?
Niitsu: Some people may feel uneasy, but in fact, similar "digital pills" have already been approved by the FDA (Food and Drug Administration) in the United States and are being used in clinical settings. The semiconductor chip is exposed inside the body after the pill dissolves, but the chip being developing in our research is approximately 1 mm square. Even if it were absorbed into the body, the amount of metal would be comparable to trace metals found in everyday foods such as those in small fish, and is therefore considered "safe" under current regulatory standards. Whether it is safe to take every day is still being carefully verified, but the current assessment is "the amount of material involved is less than what people typically ingest in daily life."
The chip is 1 mm squared, but what does it actually look like? When I hear the words "semiconductor chip," I picture components with lots of "millipede-like" legs attached to circuit board...
Niitsu: (Laughs) It doesn't look like "millipede" at all. Semiconductors are fabricated on disk-shaped wafers in a factory, and after various processing steps, are cut out from the wafer as square pieces. As those cut pieces have sharp edges, we encase the chip in a skirt-shaped housing to make it harmless inside the body. The end result looks like a "small, rounded granule."
Fascinating. Now, the key term in this research, "stomach acid charging," is also something I have never heard before. How does it work?
Niitsu: It works on the same principle as a lemon battery. By inserting two different metal electrodes into an acidic liquid (in this case, stomach acid), a chemical reaction generates electricity. That power is then used to charge a capacitor (a charge-storage component) inside the semiconductor chip. The chip generates and stores power in the stomach and continues to function as a sensor even after moving into the intestine.
How long does charging take, and for how long can monitoring continue?
Niitsu: Charging itself takes only a few seconds, but the amount of power that can be stored is very small. Currently, the 1 mm-square semiconductor chip incorporates a capacitor of approximately 10 nanofarads (nano meaning one-billionth; the farad is the unit of electrical capacitance) using ultra-low-power circuits in the picowatt range (pico meaning one-trillionth). Our near-term goal is 24-hour monitoring, but at present we can manage only a few minutes to several tens of minutes. We aim to achieve longer monitoring times as circuit and energy-storage technologies advance.
Is " stomach acid power generation" itself a rare technology?
Niitsu: Research on stomach acid power generation is underway at universities and research institutions both in Japan and abroad, but what is new here is the "technology for storing power in a system that operates entirely within an integrated circuit." Previously, external capacitors or secondary batteries were used, but in our approach we stack metal layers such as aluminum within the integrated circuit itself to store charge as a capacitor.
What is the key feature of this technology?
Niitsu: It is the vertical stacking of circuits. Stomach acid generates about 1.2 V (volts), and to increase the amount of charge stored, you would ideally raise this voltage to, say, 20 V or 30 V. However, with current circuit technology, applying such high voltages directly would destroy the circuit. So, we stacked the target circuits in multiple stages, which allowed us to lower the voltage across each individual circuit. As a result, we were also able to reuse the current flowing through the circuit, which further improved current efficiency. This idea was inspired by low-power technology used in Bitcoin (cryptocurrency) mining chips. It is fascinating that insights from the commercial industry can be applied to medical technology as well.
How is the data collected transmitted to the outside of the body?
Niitsu: The most practical approach at present is to use a patch-type receiver worn on the abdomen, which then transfers data to a smartphone or similar device. Transmitting data from inside the intestines to the body surface is technically challenging, but we are exploring the possibility using low-frequency, low-power communication. In the future, we would like to find ways to send data more directly to a smartphone or similar device.
The swallowed digital pill generates power from stomach acid and monitors the gut environment. Data is transmitted in real time to the patch.
How does this research fit into the Moonshot R&D Program Goal 1 ARAI Project: "Structuring Spatiotemporal Environmental Information in the Body Using In-body Cybernetic Avatars"?
Niitsu: The ARAI Project I am part of aims to "acquire and structure environmental information from anywhere inside the body in real time."
Our digital pill technology, which can gather environmental data such as gut temperature and pH "simply by swallowing" a pill, is exactly the kind of foundational technology needed to realize "in-body cybernetic avatars." By taking the pill regularly, it will become possible to monitor gut conditions, including the microbiome and digestive function, over time, which can contribute to health management and early disease detection.
Furthermore, if multiple pills can work together to make a wide area inside the body "visible," new possibilities will open up for personalized health advice and innovative medical care.
What kind of future would this technology bring if it became widely used?
Niitsu: The ideal is a society in which just taking a pill every day is enough to understand your gut environment and manage your health or prevent disease.
Imagine an era in which you can hear your "body's voice" in real time, knowing that "my gut pH is mildly acidic today, so I feel good," or "my microbiome is out of balance, so I should reconsider my diet." If image sensors could also be integrated, a future in which you can visually check the state of your gut or have AI automatically suggest health improvements is not out of reach.
Could you also tell us about your career? Is developing semiconductors for medical applications different from general semiconductor development?
Niitsu: I have been working on integrated circuit design since my student days. Biological and medical applications are a field that semiconductor manufacturers have been reluctant to enter, because the development cycles are long, demand is hard to forecast, and certification requirements are stringent. Precisely for that reason, I feel "if I do not take it on, this future will never open up," so I keep pushing forward. The field is still largely uncharted, but the more I do, the more excited I get about its potential social impact and new applications.
Finally, what was the most challenging aspect of this research, and what are your dreams for the future?
Niitsu: The biggest challenges were "completing the entire stomach acid charging and energy storage cycle within a semiconductor circuit alone" and "developing new high-voltage charging technology." There is still much to be done, but I want to bring down costs and make this a technology that everyone can use. I am aiming for an era in which "in-body monitoring" is available at an accessible price. Looking further ahead, I hope to realize an "in-body cybernetic avatar society" in which multiple points inside the body can be monitored simultaneously and AI for optimal health management can be achieved with the help of AI.
