Sensor to Swallow Sensor Transmits Temperature from the Body

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Accurate body temperature is an important parameter for measuring infections, inflammation, or heat stress. However, while wearables on the skin can be influenced by the environment, a sensor inside the body would be significantly more precise.

The idea of packaging diagnostics into a swallowable capsule originated over 20 years ago with capsule endoscopy. These camera pills examined the small intestine by providing high-resolution images from areas that were difficult to access with traditional endoscopy. However, previous systems were often bulky and power-hungry.

The new development from MIT now impresses with a drastically reduced size and a clever energy concept. While conventional diagnostic capsules are often quite large, the researchers managed to reduce the form factor to the point where swallowing it is as safe as drinking a sip of water.

Sensor Technology Requires 10 Nanowatts

The core of the system is a custom silicon chip with an area of only about 1 mm², which is consistently optimized for minimal self-consumption. The entire sensor system requires only about 10 nanowatts during operation. To meet this requirement, the researchers integrated a standard 1.55 V button cell. Although this battery occupies the majority of the volume of the capsule, which measures just 6 mm x 4 mm (approx. 0.24 by 0.16 inches), its extremely low power consumption enables continuous monitoring over very long periods.

The real technological breakthrough lies in the communication technology. Instead of generating its own energy-intensive radio signal like Bluetooth or Wi-Fi, the capsule uses the principle of RF backscattering—a method similar to that of passive RFID technology: an external reader close to the body emits a high-frequency signal. The tiny antenna inside the swallowed capsule captures this signal, modulates it with the temperature data, and reflects it back. Since the sensor only modifies and mirrors the signal instead of actively generating it, the energy requirement for the radio transmission is reduced to almost zero.

Multi-Level Encapsulated Sensor

The hardware must withstand extreme conditions. Stomach acid creates a highly corrosive environment that would quickly degrade conventional materials. The developers' solution is a multi-layer encapsulation made from biocompatible polymers. This encapsulation is chemically resistant while simultaneously not impairing thermal conductivity. This ensures that the sensor's response time is not affected by the protective coating.

From the Clinic to Extreme Sports

This development opens up a growing market for medical electronics beyond stationary diagnostics. In addition to clinical monitoring of patients after surgeries, the technology offers enormous potential in occupational safety and professional sports. Firefighters on duty or professional athletes in hot climates could be warned in real time of an impending heat stroke through the ingestible sensor. External sensors are often inaccurate in such extreme scenarios as they can be affected by sweat and ambient heat.

The digital interface also enables seamless integration into modern healthcare ecosystems. The data can be transmitted via a smartphone hub directly to the cloud or a medical dashboard.

The work of the MIT researchers highlights how medical electronics are evolving from bulky external devices to "invisible" internal systems. For system designers and hardware developers, this means that expertise in energy-efficient radio technology, power management, and specialized packaging is becoming increasingly important. The new sensor is an example of how semiconductor technology continues to blur the line between digital diagnostics and the biological organism.