Fluoroscopic control of a magnetorobotic capsule for precision gastrointestinal sampling and delivery

This study introduces G-Bot, an electronics-free magnetorobotic capsule designed for precision gastrointestinal (GI) sampling and localized payload delivery under standard clinical fluoroscopy. The device combines a soft inner pump (Ecoflex elastomer body with four NdFeB-particle composite ring magnets arranged in an attractive dipole mode) with a rigid protective outer shell. A two-regime magnetic actuation strategy is demonstrated: low, near-uniform magnetic fields provide robust orientation control without triggering deformation, while substantially higher field gradients generate radial inward collapse of the magnetic rings to actuate on-demand payload release or suction-based sampling. The authors quantify fluoroscopic visibility of the capsule relative to clinical iohexol standards and show that G-Bot exceeds commonly used contrast benchmarks, supporting real-time C-arm guided localization. Performance is evaluated in benchtop phantom environments across a range of viscosities, including liquid iohexol and viscous/highly viscous gelatin media, demonstrating repeatable sampling volumes (~0.2–0.3 mL) and controlled payload delivery without premature leakage. A colon-phantom demonstration integrates navigation/orientation and triggered delivery under fluoroscopic guidance at radiation exposure levels reported to be below common GI fluoroscopic procedures. The work positions G-Bot as a scalable platform for site-specific microbiome sampling, targeted therapeutic delivery, and longitudinal monitoring in GI disease, while outlining future needs including miniaturization, certified ingestible materials, and testing in anatomically realistic phantoms and in vivo models.