A pill that confirms you actually swallowed your medicine

By Vijay Kumar MalesuReviewed by Lauren HardakerJan 12 2026

By using a temporary Faraday-cage coating that dissolves in minutes, the SAFARI capsule delivers highly specific proof of pill ingestion, without batteries, retrieval, or long-term electronic waste.

Study: Bioresorbable RFID capsule for assessing medication adherence. Image credit: Grycaj/Shutterstock

In a recent study published in Nature Communications, researchers developed and tested Smart Adherence via FARaday cage And Resorbable Ingestible (SAFARI), which confirms ingestion once its protective coating dissolves in the stomach and activates a passive RFID tag, using a temporally gated shielding strategy to ensure signal specificity only after ingestion.

Why adherence verification needs a new approach

Each year, medication non-adherence leads to 125,000 preventable deaths and costs over $100 billion in the United States. Missing doses is not merely forgetfulness; it can worsen diabetes and hypertension, interfere with HIV treatment, and increase drug-resistant infections. Most adherence checks rely on self-reporting, refill data, or smart bottles that can be deceived.

Ingestible electronics can confirm swallowing, but many designs leave behind non-degradable parts, raising concerns about long-term gastrointestinal damage and electronic waste. Environmentally friendly systems that verify ingestion without the need for batteries or retrieval could make monitoring easier in healthcare. More research is necessary to confirm safety, reliability, and usability in humans.

How the SAFARI capsule was engineered

The research team created a passive RFID tag using a thin cellulose acetate base, a polyglycol sebacate bioadhesive, patterned zinc foil antenna traces, and an RFID microchip that is not bioresorbable but is small and biocompatible. They protected the electrical contacts with poly(lactic-co-glycolic acid). The tag was shaped to fit a size-000 gelatin or hydroxypropyl methylcellulose capsule together with a payload.

To create an “off” state, they coated the capsule with an EMI shield made from hydroxyethyl cellulose mixed with molybdenum or tungsten microparticles. This formed a Faraday cage that remained until dissolution in gastric fluid, preventing premature detection prior to ingestion and enabling temporally gated activation only within the stomach. They measured electrical performance using a reader and panel antenna, tracking the received signal strength indicator across the UHF band near 915 MHz.

The effectiveness of the shielding was assessed with near-field probes and a vector network analyzer. Researchers also evaluated the mechanical integrity of the capsule during loading using finite element analysis. To test feasibility, they used Yorkshire swine after endoscopic delivery to the stomach. X-ray imaging confirmed capsule position, and readings captured the tag's identity and frequency during dissolution. They measured metal ion release in simulated gastric fluid with inductively coupled plasma optical emission spectrometry and checked the breakdown of hydroxyethyl cellulose using Fourier transform infrared spectroscopy.

Transient shielding enables reliable stomach-specific activation

The SAFARI concept combined a zinc-foil RFID antenna with a temporary shield, keeping the tag inactive until it reached the stomach. This approach also reduced false positives and avoided devices that require charging, retrieval, or disposal. Bench testing showed the zinc tag resonated at 915 MHz and could be read at a distance of approximately 10–20 centimeters with stable received signal strength values. The readings stayed within FCC limits when measured in air, inside a gelatin capsule, and within excised swine stomach tissue.

Finite element simulations indicated that bending the tag to fit a size-000 capsule did not disrupt the antenna-chip connection. When immersed at body temperature (37 °C) in simulated gastric fluid or real gastric fluid, the zinc antenna and encapsulation degraded in less than one week. The softened cellulose acetate substrate degraded more slowly over several weeks, but was designed to soften and pass through the gastrointestinal tract.

For the “switch,” researchers developed a printable EMI coating using hydroxyethyl cellulose and metal microparticles. Molybdenum fillers resulted in the lowest sheet resistance, reaching approximately 0.8 ohms per square at a hydroxyethyl cellulose to molybdenum mass ratio of about 1:11. Scanning electron microscopy revealed a uniform particle distribution.

Radiofrequency transmission tests, conducted from 700 megahertz to 1.2 gigahertz, revealed that the molybdenum composite exhibited greater attenuation than tungsten. At 915 MHz, the molybdenum composite achieved shielding effectiveness close to 25 decibels, while tungsten reached around 15 decibels. This was consistent with a Faraday-cage mechanism that blocked incoming and outgoing radiofrequency energy. Measurements indicated that the coating and tag occupied a small portion of the capsule’s space, leaving most of the volume available for medication.

In live swine, endoscopy and X-ray imaging confirmed capsule position and tracked dissolution during realistic clinical procedures. The coating swelled on contact with gastric fluid. It activated the device within approximately 0.5–3 minutes, changing the device from an “off” to an “on” state and allowing continuous external reads of the tag’s identity and operating frequency.

Across multiple devices, signals captured in the stomach remained in the ~900–925 MHz range, even when tags were floating or fully immersed in gastric fluid. In vitro ion-release testing found increasing concentrations of zinc and molybdenum over three days, with zinc peaking at approximately 5 parts per million by day one and reaching saturation by day three, as components broke down. In vivo safety checks revealed no significant increase in serum zinc or molybdenum levels after dosing, providing early safety signals in swine, which aligns with these metals being essential micronutrients and with dietary intake exceeding the amounts in the capsule.

SAFARI offers ingestion-specific adherence data without batteries

The findings indicate that a component-level bioresorbable RFID capsule can confirm pill ingestion while reducing electronic waste. By keeping the tag inactive until the Faraday-cage coating dissolves in the stomach, the system may provide highly specific ingestion confirmation signals by temporally gating radiofrequency communication, thereby going beyond self-reports or smart bottles.

Such confirmation could be valuable in targeted, high-impact clinical settings, such as opioid stewardship and HIV therapy, where missed doses can have serious effects. However, the microchip still passes through the gut, and its performance must be validated across different diets, mobility patterns, and real-world reader placement scenarios, such as wearable or environmental antennas. Larger human trials and long-term safety observations, rather than mass-market deployment, are essential before adoption, in line with WHO priorities.