RoSE — Robotic Soft Esophagus for Endoprosthetic Stent Testing

Background

Stents keep the lumen open — until migration or buckling undoes the therapy.

Cross-section and free body diagram of stented esophagus showing applied radial force and hoop stress — **Fig. 1 — Clinical mechanics** Why RF and hoop stress matter once a SEMS is implanted.

Isometric view. Panel A sketches an esophagus with an implanted covered SEMS holding lumen patency against the wall.

Esophageal stenting is a fast, cost-effective therapy for dysphagia from malignant strictures. Yet 30–50% long-term cases still struggle with migration driven by continuous peristaltic forces.

Radial force (RF) on the wall is pivotal for fixation, but clinical guidance remains thin: few randomized trials, and manometry or fluoroscopy on patients after stenting is ethically and practically constrained. Bench tests (compression, expansion, corrosion) miss the soft, rhythmic environment of a living esophagus.

RoSE closes that gap: a bio-mimicking soft conduit that can impose symmetric contractions or traveling peristaltic waves while you implant commercial stents, measure RF, watch migration, and read intrabolus pressure signatures (IBPS) for texture-modified boluses.

The system

A soft, layered esophagus that swallows on command

Full experimental setup first — then tap a component to inspect the CAD / paper figures.

Full RoSE benchtop setup: starch-thickened bolus poured into funnel for peristaltic transport, with pneumatic valves and control electronics — **Full experimental setup** Starch-thickened bolus formation and transport on the complete RoSE benchtop apparatus.

Bolus pour. A starch-thickened liquid (texture-modified food simulant) is poured into the inlet funnel to form the bolus that RoSE will transport under peristalsis.

Actuator

12 axial layers

Regular pneumatic whorls (10 mm) stack along 185 mm of actuating conduit. Overlapping sequential pressurization yields continuous occlusion waves.

Fig. 2 — Side and top sectional view of robotic soft esophagus (RoSE).

210 mmconduit length

20 mmrest diameter

0–71.5 kPaoperating pressure

20–40 mm/swave velocity

40–60 mmwavefront length

Method

Three protocols on one soft platform

Symmetric loading for RF, peristalsis for migration, and catheter manometry for swallow efficacy. Use the chips to walk each figure.

Experimental setup for stent radial force measurement in RoSE — **Radial force setup** FSP + stent under cyclic cylindrical contraction.

Deploy. A force-sensing potentiometer (FSP) hoops the stent while all 12 layers inflate and deflate together, tracing hysteresis between resistance and outward force.

RoSE manometry test setup — **Manometry** IBPS under peristalsis with and without stents.

Catheter. A 5-sensor motility catheter sits at layer L₄ while starch-thickened boluses (72–144 g·L⁻¹) ride the wave.

Relative stent migration displacement plots — **Migration** Displacement vs peristalsis cycles, dry and with bolus.

TOF marker. A distal paperboard marker and time-of-flight sensor record axial stent travel under sinusoidal waves.

01

Symmetric RF

Uniform chamber pressure maps RRF / COF hysteresis and radial stiffness for each stent.

02

Peristaltic migration

Wave speed and wavelength combine with bolus viscosity to push or reverse stent drift.

03

Swallow efficacy

IBPS and transported volume reveal when a stiff buckled stent starves bolus transport.

Results

Numbers that separate a soft stent from a stiff one

Animated counters and histograms distilled from the Soft Robotics experiments. Stiffer stent B doubles radial stiffness and spikes COF — then buckling can crash bolus volume.

0 Stent A radial stiffness

0 Stent B radial stiffness

0 Stent B COF (at p₃)

0 Stent A elongation @ 50 kPa

Radial stiffness histogram Mean ± SD · N·mm⁻¹

Stent B is roughly twice as stiff as stent A under the same RoSE loading.

Chronic outward force (COF) At expansion point p₃ · N

Soft stent A stays near 0.33 N; stiff stent B holds ~18 N outward force.

Axial elongation under load Chamber pressure 50 ± 0.35 kPa · %

Compliant stent A stretches more, keeping RF on a lower profile.

Bolus library Thickener concentration vs viscosity

IDDSI-style starch boluses from syrup-thin (I) to pudding-thick (III).

Transported bolus volume with buckled stent B Mean volume per peristalsis cycle · ml

After buckling, volume collapses for thicker boluses — a mechanical path to recurrent dysphagia.

Test matrix coverage Manipulated parameters in the RoSE protocol

Each stent sees a 2 × 3 × 3 × 3 design across stiffness, bolus, speed, and wavelength.

Paper figures · guided reading

What each result figure is showing

Tap the chips under a figure to step through the panels and takeaways.

RF testing hysteresis plots for stents A and B — **Fig. 9 — RF hysteresis** Cyclic contraction/expansion maps RRF and COF for stents A and B.

Hysteresis. Loading (RRF) and unloading (COF) do not retrace: the stent can stay soft while expanding yet resist hard when compressed — useful for lumen patency without constant high force.

Normal versus buckled stent in RoSE — **Fig. 11 — Buckling** Stiff stent B can leave the circumferential plane under compression.

Normal. Left: an implanted stent remains roughly circular, preserving conduit compliance for bolus passage.

Manometry IBPS results with and without stents — **Fig. 10 — Manometry results** IBPS, gradients, and transported volume across bolus / wave conditions.

Pressure trace. Spatiotemporal manometry shows IBPS at the bolus tail versus contact pressure once the lumen seals on the catheter.

Quarter RoSE sectional model with marker trajectories — **Fig. 13 — Quarter RoSE (QSR)** One-fourth axial section made to visualize peristalsis inside the conduit (Movie S3).

Sectional cut. The quarter RoSE (QSR) keeps one chamber per layer along the length so the traveling occlusion wave can be filmed from the side — visibility the full conduit hides.

Publication

Soft Robotics paper & citation

RoSE: A Robotic Soft Esophagus for Endoprosthetic Stent Testing

Dipankar Bhattacharya, Sherine J.V. Ali, Leo K. Cheng, Weiliang Xu

Soft Robotics, Volume 8, Issue 4 · First published online 4 August 2020

University of Auckland · Riddet Institute · Auckland Bioengineering Institute · MedTech CoRE

Version of Record Read paper

Bhattacharya D, Ali SJV, Cheng LK, Xu W. RoSE: A Robotic Soft Esophagus for Endoprosthetic Stent Testing. Soft Robotics. 2021;8(4). doi:10.1089/soro.2019.0205

Supplementary movies

Watch RoSE contract, swallow, and reveal peristalsis

Select a chapter. Movies S1–S3 from the Soft Robotics submission. Movie S3 uses the quarter RoSE (QSR) — a one-fourth axial section — so the peristaltic wave is visible.

Movie S1 — Symmetric contraction