SpongeBot: A Soft Magnetic Mini-Robot for Controlled Gastric Cell Sampling *

Abstract

Early detection of gastrointestinal (GI) cancer is critical for improving treatment outcomes and survival rates. Yet conventional endoscopic techniques remain invasive and labor-intensive, thus presenting significant challenges for cancer screening on large populations. Current commercially available sponge-based sampling devices are passive and limited in their reach to the esophagus, hindering comprehensive sampling in the stomach. Here, for the first time, we report the SpongeBot – a non-invasive soft mini-robot designed for active cell sampling in the upper GI tract, with a particular focus on the stomach. The SpongeBot integrates an open-cell sponge and a magnetic actuator, enabling precise and controlled sampling under a wireless external magnetic field. To accommodate the intricate anatomy of the stomach, the robot is capable of transitioning between two modes of motion — the navigation and the sampling mode, allowing trajectory control and targeted sampling at desired locations. Kinematic model is established to accurately represent the locomotion of the robot on wet mucosa surfaces. Pilot testing on ex vivo porcine stomachs is successfully performed with sufficient cells sampled for subsequent clinical laboratory testing. Histological analysis shows the sampling causes no detectable damage to the mucosa layer. SpongeBot has the potential as a cell sampling device for the upper GI tract to be deployed in primary care settings for cancer prevention.