Aim:

We developed a magnetically programmable soft robot that can crawl, self-orient toward a tissue interface, store liquid cargo in an internal microporous reservoir, and achieve on-demand directional cargo release toward a desired tissue interface under external magnetic field.

Challenge:

Inflammatory bowel disease (IBD), mainly including Crohn’s disease and ulcerative colitis, is a chronic condition that causes inflammation in the gastrointestinal (GI) tract. IBD affects more than 3 million adults in the United States and is estimated to cost approximately $50 billion annually. Developing targeted drug delivery platforms for time- and location-restricted therapies recognized as a priority IBD treatment by Crohn’s & Colitis Foundation.

Existing technologies, including smart polymer-coated pills and electronic capsule robots, may either lack precise localization to specific lesion areas or require complex, costly systems. For gastrointestinal applications, nondirectional release can waste therapeutic payload and reduce localized absorption at the intestinal tissue interface.

Solution:

We propose a soft robotic design that integrates a liquid reservoir directly into the robot body using an interconnected microporous magnetic elastomer, enabling liquid cargo storage while preserving programmable shape morphing and locomotion. A thin microcrystalline wax film seals the release port during transport. The robot is magnetically programmed with a spatially distributed magnetization profile that enables controlled locomotion under low external magnetic fields and self-correcting flipping, allowing the release interface to align toward the intestinal wall before release. A higher magnetic field then bends the robot sufficiently to rupture the wax seal and trigger directional liquid release.

Technique:

The robot is assembled from magnetic silicone elastomer layers, a porous cargo-storage unit, and a 31 µm-thick wax sealing layer. The total device size is 8 × 24 × 1.2 mm. The porous unit has an average porosity of 49.3% ± 1.6%, enabling a liquid cargo loading capacity of 41.4 µL. Its magnetic profile is encoded using a 1.2 T pulse magnetizer. Low magnetic fields generate crawling deformation and orientation control, while cargo release is activated only after the field reaches a higher rupture threshold. Experiments demonstrated 100% flipping success at 2 mT, a release threshold of 8.37 ± 0.85 mT, no visible leakage during cyclic low-field locomotion in aquatic environment, and ex-vivo locomotion and directional release in large intestine tissue was achieved. The estimated material cost is less than $0.06 per device.

Value:

The platform combines untethered magnetic actuation, directional tissue-facing on-demand liquid cargo release, and soft-body deformability in a centimeter-scale system. This could support future localized treatment strategies in GI tract.