Page 461 - Flexible Robotics in Medicine

CHAPTER 20

Thermo-responsive hydrogel-based circular

valve embedded with shape-memory

actuators

1
1,2
Manivannan Sivaperuman Kalairaj , Hritwick Banerjee , Keith Gerard Lopez 1
and Hongliang Ren 1
1 2
Faculty of Engineering, National University of Singapore, Singapore, Max Planck Institute for
Intelligent Systems, Stuttgart, Germany

This chapter is to qualitatively analyze, compare, and evaluate a thermo-responsive hydrogel-
based valve and a hydrogel-based valve embedded with a shape memory alloy (SMA) actuator,
which could possibly be used in biomedical fluid control processes. The thermo-responsive
hydrogel valve (TRHV) was found to increase its lumen area with temperature increase and
vice versa. Based on experiments, the expansion and contraction percentages of the TRHV
lumen were found to be highest in the valve with dimensions, 10 mm outer diameter and 4 mm
depth. TRHV demonstrated a maximum change in lumen area of 12.55 mm2 (266% of its

initial area) at 40 C. The maximum expansion of 266% of its initial lumen area is achieved in

TRHV at 40 C. The time response for the thermo-responsive hydrogel to respond to
temperature stimuli and achieve a stable target lumen was 100 seconds. The shape memory
alloyactuated hydrogel valve (SMAHV) were tested for two designs, SMA wire-based SMAHV
and SMA spring-based SMAHV with different wire diameters. Both the SMA wires and
springs in the SMAHV required 25 seconds of actuation time, while a cycle was completed in
8 seconds. The SMA wirebased SMAHV displayed a maximum displacement of 1 mm with
250 µm diameter SMA wire, and the SMA spring-based SMAHV displayed a maximum
displacement of 0.9 mm with 100 µm diameter SMA wire. The high temperature produced
during the actuation of SMA is trapped by the encapsulating hydrogel layer and protects the
environment.

20.1 Introduction

Continuous bladder irrigation (CBI) is a supplementary procedure that provides a continuous
input of sterile solution into the bladder to remove loose tissue and blood clots and maintain

Flexible Robotics in Medicine.
DOI: https://doi.org/10.1016/B978-0-12-817595-8.00021-3 455
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