Magnetic soft robot folds to navigate the gut and deliver drugs on target

Mar 14, 2026

A flexible magnetic soft robot using magnetorheological fluids navigates the gastrointestinal tract, folds to fit narrow passages, and delivers drugs to targeted lesion sites.

(Nanowerk News) Researchers have developed a thin, flexible magnetic soft robot that can navigate the gastrointestinal tract, fold itself to pass through narrow intestinal passages, and deliver drugs directly to targeted lesion sites. The device, built from magnetorheological fluids sandwiched between soft polymer layers, changes its magnetization direction in real time, allowing remote steering through complex biological environments without a physical tether. The work was led by Xinhua Liu at China University of Mining and Technology and Ting Zhang at Soochow University, in collaboration with researchers at RWTH Aachen University and the University of Oxford. Their findings were published in SmartBot (“A Folding Magnetic Soft Sheet Robot With Real‐Time Reconfigurable Magnetization for Targeted Drug Delivery”).

Key Findings

Gastrointestinal diseases affect millions of people globally, yet conventional oral drug delivery distributes medication throughout the body rather than concentrating it at the site of disease. This reduces therapeutic efficiency and increases the risk of side effects. Magnetic soft robots offer an alternative by carrying drug payloads directly to affected tissue, but previous designs have struggled with limited folding angles, fixed magnetization patterns, and poor adaptability to the irregular shapes inside the stomach and intestines. (a) Structural decomposition diagrams of the soft sheet robot and magnetorheological fluids. (b) Diagram of the 3D model of the soft sheet robot. (c) Microstructure diagram of magnetorheological fluids based on fluorescence calibration. (d) Prototype of the soft sheet robot. (e) Magnetization curves of magnetorheological fluids for 5 magnetic particle densities. (Image: China University of Mining and Technology) The new robot measures 30 mm long, 10 mm wide, and 1.5 mm thick, weighing just 0.55 grams. Its four-layer structure consists of upper and lower linear low-density polyethylene films, a magnetorheological fluid core, and a polyamide nylon mesh for structural support. Magnetorheological fluids contain suspended magnetic particles that form chain-like structures along the direction of an applied magnetic field within milliseconds. When the external field is removed, the particles disperse and the material loses its magnetization. This means the robot carries no residual magnetic signature inside the body when it is not being actively controlled, eliminating unintended magnetic interference with surrounding tissue. Rather than relying on permanently magnetized segments that lock a robot into predefined folding patterns, the magnetorheological fluid core allows the magnetization direction to change dynamically as the external field orientation shifts. A five-degree-of-freedom magnetic field platform drives the robot through a combination of flip, steering, and folding motions. When folded, the robot reduces its surface area to roughly one-third, narrow enough to pass through tight intestinal sections. Once inside the larger stomach cavity, it unfolds to its full dimensions for stable movement. This lets a single device adapt to the dramatically different spatial constraints found across the gastrointestinal tract. The team built five prototypes with magnetorheological fluid densities ranging from 3.0 to 4.2 grams per milliliter and tested them across multiple surface conditions. The robots performed stable flipping, steering, and folding on smooth surfaces, flexible fluff surfaces, and inclined surfaces, as well as underwater. Even while carrying biodegradable hydrogel drug capsules weighing 0.15 grams, roughly 30 percent of the robot’s own mass, movement remained reliable. This load capacity is relevant because the robot must transport a therapeutic payload without compromising its ability to navigate and fold. The most telling validation came from ex vivo experiments using porcine stomachs, which closely mimic the human gastrointestinal environment. In 10 repeated trials, the robot navigated to any designated lesion position within an average of five minutes and attached stably at the drug release site. The hydrogel payload dissolved within 30 minutes, delivering its contents locally. Throughout these tests, ultrasonic imaging using a Voluson E10 system tracked the robot’s position and movement in real time inside the closed gastric cavity. This confirmed that clinicians could monitor and guide the device during operation, an important requirement for any future clinical use. Safety testing addressed the harsh chemical conditions of the digestive system. The robot was immersed in simulated gastric juice at pH 1.2 and simulated intestinal juice at pH 6.8, both held at 37 degrees Celsius for 24 hours. After exposure, the device showed no surface rupture, swelling, or shape change. Analysis of the surrounding fluids detected no heavy metals or harmful substances above safety thresholds. Microbial cultures revealed no bacterial colony growth, confirming the robot’s biocompatibility and nontoxicity in gastrointestinal conditions. Liu is a researcher at the School of Mechanical and Electrical Engineering at China University of Mining and Technology, based in Xuzhou, Jiangsu Province. His work focuses on magnetic robots, magnetorheological materials, and biomedical engineering applications, with more than 150 published papers and over 60 national invention patents. The university has particular strengths in mechanical and electrical engineering, materials science, and biomedical engineering, and maintains collaborative ties with domestic and international research institutions. Future work will target the practical challenges of operating inside a living digestive system, including acidic gastric conditions, peristaltic contractions, and fluid disturbances. The team also plans to tighten the coordination between magnetic field control and ultrasonic detection to allow more precise steering during clinical procedures.