OSCAR: An Ovipositor-Inspired Self-Propelling Capsule Robot for Colonoscopy
🤖 AI Summary
This study addresses the challenge of propulsion difficulties in conventional colonoscopes caused by catheter entanglement and the slippery, viscoelastic colonic environment. Inspired by the ovipositor of parasitic wasps, the authors propose a novel self-propelled capsule robot featuring a spring-cam mechanism that drives twelve circumferential sliders in a coordinated, phase-shifted motion. By exploiting temporal asymmetry between extension and retraction phases, the design achieves controllable frictional anisotropy, generating net forward thrust under low normal loads. This work represents the first application of an ovipositor-inspired locomotion mechanism to capsule endoscopy and establishes a theoretical framework using a Kelvin–Voigt viscoelastic contact model. Ex vivo experiments in porcine colons demonstrate stable performance with a traction force of 0.85 N and a propulsion speed of 3.08 mm/s. The thrust scales linearly with phase asymmetry and is independent of velocity, meeting clinical requirements for timely examination.
Application Category
📝 Abstract
Self-propelling robotic capsules eliminate shaft looping of conventional colonoscopy, reducing patient discomfort. However, reliably moving within the slippery, viscoelastic environment of the colon remains a significant challenge. We present OSCAR, an ovipositor-inspired self-propelling capsule robot that translates the transport strategy of parasitic wasps into a propulsion mechanism for colonoscopy. OSCAR mechanically encodes the ovipositor-inspired motion pattern through a spring-loaded cam system that drives twelve circumferential sliders in a coordinated, phase-shifted sequence. By tuning the motion profile to maximize the retract phase relative to the advance phase, the capsule creates a controlled friction anisotropy at the interface that generates net forward thrust. We developed an analytical model incorporating a Kelvin-Voigt formulation to capture the viscoelastic stick--slip interactions between the sliders and the tissue, linking the asymmetry between advance and retract phase durations to mean thrust, and slider-reversal synchronization to thrust stability. Comprehensive force characterization experiments in ex-vivo porcine colon revealed a mean steady-state traction force of 0.85 N, closely matching the model. Furthermore, experiments confirmed that thrust generation is speed-independent and scales linearly with the phase asymmetry, in agreement with theoretical predictions, underscoring the capsule's predictable performance and scalability. In locomotion validation experiments, OSCAR demonstrated robust performance, achieving an average speed of 3.08 mm/s, a velocity sufficient to match the cecal intubation times of conventional colonoscopy. By coupling phase-encoded friction anisotropy with a predictive model, OSCAR delivers controllable thrust generation at low normal loads, enabling safer and more robust self-propelling locomotion for robotic capsule colonoscopy.
Problem
Research questions and friction points this paper is trying to address.
self-propelling capsule robot
colonoscopy
viscoelastic environment
friction anisotropy
locomotion
Innovation
Methods, ideas, or system contributions that make the work stand out.
ovipositor-inspired
friction anisotropy
self-propelling capsule robot
Kelvin-Voigt model
phase-encoded locomotion
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