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Research Paper

Dielectric Elastomer Jet Valve for Magnetic Resonance Imaging-Compatible Robotics

[+] Author and Article Information
Sylvain Proulx

e-mail: sylvain.proulx2@usherbrooke.ca

Jean-Philippe Lucking Bigué

e-mail: jean-philippe.lucking.bigue@usherbrooke.ca

Patrick Chouinard

e-mail: patrick.chouinard@usherbrooke.ca

Geneviève Miron

e-mail: genevieve.miron@usherbrooke.ca

Jean-Sébastien Plante

e-mail: jean-sebastien.plante@usherbrooke.ca
Department of Mechanical Engineering,
Université de Sherbrooke,
Sherbrooke, QC J1K 2R1, Canada

Manuscript received October 21, 2011; final manuscript received December 15, 2012; published online June 24, 2013. Assoc. Editor: Ming-Yih Lee.

J. Med. Devices 7(2), 021002 (Jun 24, 2013) (7 pages) Paper No: MED-11-1095; doi: 10.1115/1.4024157 History: Received October 21, 2011; Revised December 15, 2012

This paper presents the design and experimental characterization of a binary jet valve, specifically developed to control an all-polymer needle manipulator during intramagnetic resonance imaging (MRI) prostate interventions (biopsies and brachytherapies). The key feature of the MRI-compatible valve is its compact dual-stage configuration. The first stage is composed of a low-friction jet nozzle, driven by a small rotary dielectric elastomer actuator (DEA). The second stage provides sufficient air flow and stability for the binary robotic application through an independent air supply, activated by a bistable spool. A hyperelastic stress-strain model is used to optimize the geometrical dimensions of the DEA jet assembly. Fully functional valve prototypes, made with 3M's VHB 4905 films, are monitored with a high-speed camera in order to quantify the system's shifting dynamics. The impact of nozzle clearance, dielectric elastomer film viscoelasticity, mechanical friction, and actuator torque generation on overall dynamic behavior of two different valve setups is discussed. Results show an overall shifting time of 200–300 ms when the friction of the nozzle and DEA actuation stretches are minimized. Low shifting time combined with compactness, simplicity, and low cost suggest that the low friction DEA-driven jet valves have great potential for switching a large number of pneumatic circuits in an MRI environment as well as in traditional pneumatic applications.

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Figures

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Fig. 1

Laboratory prototype of an elastically averaged binary manipulator that uses solenoid air valves (left) and a conceptual binary manipulator that integrates MRI-compatible DEA valves within the MRI bore (right)

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Fig. 2

Overall and section view of the dual-stage MRI compatible valve

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Fig. 3

Unactuated (left) and actuated DEA (right)

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Fig. 4

Section view of stage 1

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Fig. 5

Forces exerted on the jet assembly and geometrical parameters

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Fig. 6

Design spade for h1 = 1 mm and V = 6.5 kV

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Fig. 7

Illustration of the clearance in valve designs D1 and D2

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Fig. 8

Design D1: shifting curves

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Fig. 9

Design D2: shifting curves

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Fig. 10

Influence of nozzle clearance on the pressure inside the chamber and on the reaction force on the nozzle

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Fig. 11

Schematic view (left) and photo (right) of the experimental setup used for valve characterization

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Fig. 12

Design D1: torque measurements of the jet assembly at different angular velocity

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Fig. 13

Design D2: torque measurements of the jet assembly at different angular velocity

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