Ionic polymer metal composite (IPMC) is an ideal material for underwater biomimetic robots. Its softness is very helpful
for generating biomimetic motion. Because IPMCs naturally contain water they do not require extra sealing. The
resulting robot can be soft and lightweight. Previous research on swimming robots is focused on robots swimming in
water. In our study we compare the suitability of two different locomotion patterns - tail oscillation and body undulation,
for swimming in viscous fluid. We found that in water both patterns could propel the robot by generating vortices behind
the robot body. In viscous fluid the robot could be propelled only by body undulation without much disturbance of
nearby fluid. Unlike tail oscillation, the whole body undulation was shown to be a suitable pattern for locomotion in both
water and viscous fluid.
We present a new approach to the fabrication of soft dielectric elastomer actuators using a 3D printing process.
Complete actuators including active membranes and support structures can be 3D printed in one go, resulting in a great
improvement in fabrication speed and increases in accuracy and consistency. We describe the fabrication process and
present force and displacement results for a double-membrane antagonistic actuator. In this structure controlled prestrain
is applied by the simple process of pressing together two printed actuator halves. The development of 3D printable
soft actuators will have a large impact on many application areas including engineering, medicine and the emerging field
of soft robotics.
This paper discusses a model of IPMC sensors and the characteristics of the frequency responses. There are
two different methods of measurements, the current sensing and the voltage sensing, which exhibit completely
different frequency responses each other. A simple model based on Onsager's equation is shown in order to
explain the experimental results of the current sensing. The voltage sensing model is derived by the equivalent
transform of the voltage and the current sources. In contrast to the constant gain of the charge response, the
characteristics of the voltage response are directly related to the impedance dynamics. In the experiments, the
frequency responses of the charge/current sensing and the voltage sensing for two species of counter ion are
measured. The ratio of the obtained frequency responses and the measured impedance are also compared to
validate the voltage sensing model. Though the theoretical prediction of the sensor coefficient does not match
the experimental one, the structure of the model agrees with the experimental data.
The emergence of soft polymer actuators brings a great deal of excitement in the robotics and biomedical engineering
community because of the possibilities to easily mimic the motion of living organisms and ability to manipulate living
tissue and cells without damaging it. Some of the applications of soft polymer actuators, such as micropumps, require
them to operate at high frequency and large displacement, which usually achieved near resonance. It would be beneficial
for the designer, if he could easily tailor the frequency response and the resonance frequency to suit the operating
conditions. We propose such an effective method of modification of the frequency response of ionic polymer metal
composite (IPMC) actuators by introducing an anisotropic roughness on their surface.
We present a novel linear actuator made from a single Ionic Polymer-Metal Composite (IPMC) strip. In its simplest
form the device activates into the shape of a double-clamped buckled beam. This structure was chosen following
observation of the buckle failure modes of axially compressed beams. The practical realization of this device is made
possible by the development of new manufacturing techniques also described. The benefit of this buckled beam
structure is that bending moments in the two halves of the beam cancel each other out. As a result, only one bending
actuator is needed to form a single linear actuator and there is no need for mechanical joining of separate actuators - a
disadvantage of previous linear actuator designs. The non-rotating nature of the end fixing in the double-clamped
buckled beam also means that joining multiple elements to increase displacement or force is trivial. We present initial
experimental results of a single linear actuator and a balanced, pair-connected linear actuator.
Ionic polymer-metal composites (IPMC) are soft actuators with potential applications in the fields of medicine and
biologically inspired robotics. Typically, an IPMC bends with approximately constant curvature when voltage is applied
to it. More complex shapes were achieved in the past by pre-shaping the actuator or by segmentation and separate
actuation of each segment. There are many applications for which fully independent control of each segment of the
IPMC is not required and the use of external wiring is objectionable. In this paper we propose two key elements needed
to create an IPMC, which can actuate into a complex curve. The first is a connection between adjacent segments, which
enables opposite curvature. This can be achieved by reversing the polarity applied on each side of the IPMC, for
example by a through-hole connection. The second key element is a variable curvature segment. The segment is
designed to bend with any fraction of its full bending ability under given electrical input by changing the overlap of
opposite charge electrodes. We demonstrated the usefulness of these key elements in two devices. One is a bi-stable
buckled IPMC beam, also used as a building block in a linear actuator device. The other one is an IPMC, actuating into
an S-shaped curve with gradually increasing curvature near the ends. The proposed method of manufacturing holds
promise for a wide range of new applications of IPMCs, including applications in which IPMCs are used for sensing.
Demands from the fields of bio-medical engineering and biologically-inspired robotics motivate a growing interest in
actuators with properties similar to biological muscle, including ionic polymer-metal composites (IPMC), the focus of
this study. IPMC actuators consist of an ion-conductive polymer membrane, coated with thin metal electrodes on both
sides and bend when voltage is applied. Some of the advantages of IPMC actuators are their softness, lack of moving
parts, easy miniaturization, light weight and low actuation voltage. When used in bio-mimetic robotic applications, such
as a snake-like swimming robot, locomotion speed can be improved by increasing the bending amplitude. However, it
cannot be improved much by increasing the driving voltage, because of water electrolysis. To enhance the bending
response of IPMCs we created a "preferred" bending direction by anisotropic surface modification. Introduction of
anisotropic roughness with grooves across the length of the actuator improved the bending response by a factor of 2.1.
Artificially introduced cracks on the electrodes in direction, in which natural cracks form by bending, improved bending
response by a factor of 1.6. Anisotropic surface modification is an effective method to enhance the bending response of
IPMC actuators and does not compromise their rigidity under loads perpendicular to the bending plane.
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