While ingestible electronics aren’t new, devices that can be safely and comfortably ingested are. No one wants to (or even tries to) swallow a plastic capsule the size of a knuckle — and some people can’t.

A team of researchers at MIT recently developed a new ingestible thermometer the size of a tiny blueberry that makes it easier to obtain highly accurate core body temperature measurements.

“The vision is not to replace clinicians or existing diagnostic tools but to provide new streams of high-quality internal data that can support better decisions, earlier interventions, and more personalized care,” said senior author of the paper Giovanni Traverso, MD, PhD, professor of mechanical engineering at MIT and gastroenterologist at Brigham and Women’s Hospital of Harvard Medical School.

Taking the Temperature

Why start with a thermometer? “The motivation was both clinical and technological,” explained Saransh Sharma, PhD, associate professor of bioelectronic systems at the University of Cambridge in Cambridge, England, and lead author of the paper (Sharma was a postdoc at MIT at the time).

Clinically, temperature can provide important information about inflammation, infection, thermoregulation, impaired perfusion, and other physiologic changes. Technologically, they saw an opportunity to push miniaturization, power efficiency, and wireless communication to a point where these devices could become safer and more broadly usable, including potentially in pediatric or sensitive populations where larger capsules may not be ideal.

Making a functional thermometer was only one challenge, and the team required expertise across fields: microelectronics, antenna design, biomedical engineering, materials, and preclinical medicine.

A Tough Pill To Swallow

Ingestible devices in the form of capsules have been around for about 50 years. “The field has boomed over the past decade,” said Khalil Ramadi, PhD, assistant professor of bioengineering at NYU Tandon School of Engineering in Brooklyn, New York, who was not affiliated with the study. “It’s fueled by advances in microelectronics and engineering. The latest reported pills have seen advanced sensing functionalities, together with therapeutic capabilities to deliver drugs or electrical signals.”

The biggest hurdle to developing these devices has been getting them to a size that’s easy to swallow. “Miniaturization is not simply a matter of making the outer capsule smaller,” said Sharma. “Every component has to shrink or become more efficient: the sensor, the power source, the antenna, the circuit board, the encapsulation, and the communication system.”

In addition to the challenges of making each of the components smaller, the gut is an extremely difficult environment to operate in, with strong mechanical contractions and harsh digestive chemicals that actively try to break down devices. “Designing devices that resist these forces, while also able to perform specific functions, takes some clever engineering and materials science,” said Ramadi. “Ultimately, the largest component of any electronic ingestible device is the battery as a power source. Approaches like wireless powering can overcome this but are very difficult to implement in the gut.”

Ramadi was impressed with how small the team at MIT was able to go on their sensor. The fully encapsulated device is 6 mm in diameter and 4 mm in height and provides high-resolution internal temperature data with very low power consumption. The researchers couldn’t quite believe it themselves. “One encouraging surprise was how much functionality we could achieve in such a small form factor,” said Sharma.

Necessary New Approaches to Power

The key driver in the team’s success was their ability to shrink the battery. “Conventional sensing and wireless transmission can require relatively large amounts of energy, which means larger batteries and larger capsules,” said Traverso. “In this work, we tried to address that by designing an ultralow-power temperature-sensing circuit and using passive backscatter communication, which dramatically reduces the power burden.”

Ramadi suggested that ingestibles could soon move past traditional “onboard” power sources like batteries and tap into emerging approaches such as wireless powering, energy harvesting, or chemical batteries leveraging ion-rich gastric and intestinal fluids.

Traverso agreed. “If we add pressure, pH, biomarkers, localization, or active therapeutic functions, the energy requirements will increase,” he said. “That creates a need for better energy management, smaller batteries, and eventually energy-harvesting approaches that could draw power from the body or the external environment.”

What’s Coming

The researchers at MIT want their work to lead to more devices like the one they created: smaller, safer, and more capable. Each iteration has a two-pronged goal: less invasive and more accessible. If they can do that, a broader shift toward minimally invasive, real-time, and personalized health monitoring will happen.

Traverso’s hope for the future: “If we can continuously monitor signals from inside the body without wires, discomfort, or the need for large devices, that could open new opportunities in clinical care, remote monitoring, perioperative medicine, critical care, sports medicine, and even austere environments.”

Ramadi reported no conflicts. Disclosure information for study authors is available in the original study publication.