Evaluation of friction enhancement through soft polymer micro-patterns in active capsule endoscopy

Abstract

Capsule endoscopy is an emerging field in medical technology. Despite very promising innovations, some critical issues are yet to be addressed, such as the management and possible exploitation of the friction in the gastrointestinal environment in order to control capsule locomotion more actively. This paper presents the fabrication and testing of bio-inspired polymeric micro-patterns, which are arrays of cylindrical pillars fabricated via soft lithography. The aim of the work is to develop structures that enhance the grip between an artificial device and the intestinal tissue, without injuring the mucosa. In fact, the patterns are intended to be mounted on microfabricated legs of a capsule robot that is able to move actively in the gastrointestinal tract, thus improving the robot's traction ability. The effect of micro-patterned surfaces on the leg-slipping behaviour on colon walls was investigated by considering both different pillar dimensions and the influence of tissue morphology. Several in vitro tests on biological samples demonstrated that micro-patterns of pillars made from a soft polymer with an aspect ratio close to 1 enhanced friction by 41.7% with regard to flat surfaces. This work presents preliminary modelling of the friction and adhesion forces in the gastrointestinal environment and some design guidelines for endoscopic devices.

Microgroove cushion of robotic endoscope for active locomotion in the gastrointestinal tract

“…The groove depth is determined by the intestinal morphology, where the value of δ is defined as the distance from the top to the bottom of the GI surface corrugation. The literature shows two sections of colonic tissue with different morphologies ( δ = 1.181 mm and 0.717 mm). A millimeter‐grade depth is reasonable for the contact groove, but the complicated morphology of the GI surface hardly confirms an accurate δ .…”

A wireless capsule robot with spiral legs for human intestine

“…In former studies, micro‐motor driven capsules that were developed have been compact and short, but the hook‐ and thorn‐like legs could be potentially hazardous. Although some contact devices have employed micro‐pillar adhesives , which showed promise for some applications, the friction with currently available adhesives only increased the strength 1.5‐fold. In this research, we have attempted to address these issues by developing a safer way for a capsule robot to anchor and travel through the intestine.…”

Biomimetic Modification of Polymeric Surfaces: A Promising Pathway for Tuning of Wetting and Adhesion

“…The conformal adhesion is far less explored and understood. Several recent studies of the use of biomimetic micro/nanoscale structures for medical applications have revealed the importance of the conformal adhesion, where a strong adhesive bond as well as compliance and conformability to tissue surfaces are required 114, 140–143. Recently, we started to investigate the conformal adhesion of a polymer film on the biomimetic µm‐sized surface structures and hypothesized that the local adhesion and friction events of pulling micropillars out of the embedded polymer film would significantly enhance the global adhesion strength at the interface 4.…”