**[Responses to Reviewer's comments]{.underline}**

The reviewer's comments were very helpful and we thanks for their time
to review this paper.

According to reviewer's recommendations, some expressions are corrected
clearly and additional information is included for easiness of
understanding.

**Comments and Responses**

1.  **Section: Introduction**

    a.  "artificial muscle actuator" should be defined to the reader.

        -   In my opinion, it is not necessary to define. The
            "artificial muscle actuator" is commonly used phrase in many
            papers. For restrictive use of the mean of "artificial
            muscle actuator", the sentence is revised.

    b.  Provide examples and/or references of the "remarkable progress"
        that have been made.

        -   Some papers are referred.

    c.  "VHB" Please name the manufacturer

        -   The name of products and the manufacturers are mentioned
            clearly.

    d.  "silicone" Please provide examples of silicones that are
        commercially available and have been utilized in the fabrication
        of dielectric elastomer actuators.

        -   Some examples, such as CF19-2186(Nusil) and KE441(ShinEtsu),
            are provided.

    e.  "Furthermore they do not allow the modification of its
        properties..." This sentence is not true. There are known
        silicones which are commercially available that have been
        modified to increase the dielectric constant, decrease the
        Young's modulus range, and increase the breakdown voltage.

        -   The sentence is revised.

    f.  Fix typo: dielectric constant ![](media/image1.wmf) is used in
        this section. However in Section 2, ![](media/image2.wmf)is
        used.

        -   Symbol for dielectric constant is used
            to![](media/image2.wmf).

    g.  "stress relaxation" is not a material property.

        -   In my opinion, stress relaxation is one of viscoelastic
            property of elastomer.

    h.  "In addition, stress relaxation must be taken into account as
        important material properties..." This sentence can be improved
        by indicating why stress relaxation occurs (viscoelasticity or
        other reasons?). It can then be followed by indicating that
        stress relaxation is undesirable.

    i.  In the second paragraph, "adjusted for the actuator" is
        mentioned. Could you specify/describe the actuator you are
        referencing?

    j.  In the second sentence of the second paragraph: "In the first, "
        This phrase is missing a noun. Did you mean to say "In the first
        section,"? Also, the remainder of the paragraph is completed
        with no reference to the second, third, or fourth items.

    k.  "handling" Please elaborate on what "handling" means.

        -   For comments 1-h, 1-i, 1-j, 1-k and 2-h, the introduction
            section is revised to clearly.

2.  **Section: Requirements for elastomeric material as actuating
    means**

    a.  "driving voltage" Please define this phrase.

        -   The "driving voltage" is revised to "actuation voltage".

    b.  Equation (1) has two parts. Please describe how you obtain
        ![](media/image3.wmf) from ![](media/image4.wmf).

        -   The definition of C was an error. C must be "the capacitance
            per unit volume".

        -   The equation is described clearly.

    c.  Equation (2): You must specify that this equation is valid only
        for small linear strain. Furthermore, it is unclear how the last
        two terms of this equation are equal. Could there possibly be a
        mathematical derivation error?

        -   There was an editing error in LaTeX equation description.

        -   The equation is corrected.

    d.  Please define "mechanical pressure". Mechanical pressure is
        misleading. The pressure you are referring to is Maxwell stress.
        It is a stress that exists due to an electric field. Hence, the
        mechanical pressure you are referring to is not purely
        mechanical but electromechanical.

        -   The phrase is corrected to "Electromechanical stress".

    e.  Please provide references to papers that describe the dielectric
        constant as being one of the most important material properties
        in the dielectric elastomer.

        -   The sentence was unclear.

        -   The mean of dielectric elastomer is limited to be used for
            actuator.

    f.  Second paragraph: "According to Eq. 2, Young's modulus Y is
        required to be small to get large deformation and strain
        energy." This statement is false since it is not 'required'. It
        would be beneficial.

        -   The sentence is revised.

    g.  Second paragraph: Viscoelasticity is mentioned, however, it is
        known that VHB exhibits much greater viscoelasticity than
        silicone. I believe this warrants mentioning. Figure 8 validates
        this, too. Please support the statement with reference(s).

    h.  The second paragraph should be moved to the introduction
        section. This will allow the introduction of terms such as
        "stress relaxation" and Young's modulus.

        -   For comments 2-g and 2-h, the paragraph is revised

    i.  Third paragraph: Please provide references for the statements
        made in this paragraph. Also, terms such as "bigger" and "less
        creep" are used without reference to magnitudes or range of
        magnitudes. Please specify these magnitudes.

        -   Equations for capacitance C and Maxwell stress are derived
            to verify the relationship between mechanical creep and
            electromechanical creep.

    j.  Third paragraph: "Maxwell stress" This term is used without
        defining it first. Please define this term.

        -   The paragraph is revised.

3.  **Section: Proposed materials for dielectric elastomer actuator**

    a.  Please provide reference(s) to the statement that good
        elongation as well as adequate resilience, tensile and
        comparison set are the critical requirements in determining the
        material as a promising candidate for dielectric elastomer
        actuators?

        -   The section 3 is revised clearly.

    b.  It seems as if the terms "synthetic elastomer" and "dielectric
        elastomer" are being used interchangeably. It would be clearer
        for the reader to understand that dielectric elastomer is the
        same as synthetic elastomer and use one of the terms throughout
        the paper.

        -   The "synthetic elastomer" is indicated the proposed material
            in this paper and the term "dielectric elastomer" is used
            for general elastomer and commercial one.

        -   Some sentences are revised clearly..

4.  **Section: Comparisons of major properties**

    a.  "VHB series" is mentioned without defining what is meant by
        series. Please mention that the VHB polyacrylate elastomers come
        in rolls/sheets and are available in various thicknesses.
        Indicate thicknesses.

-   "VHB series" is clearly revised to "VHB4905" or "VHB4905/4910". And
    the thicknesses are mentioned in the introduction section.

    a.  Reference company locations for Shinetsu and Nusil.

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-   The company names are mentioned in the introduction section.

    a.  It is recommended that the thickness and size of the sheets
        shown in Figure 3 be specified.

    b.  In Figure 3, there seems to a pattern in the fabricated
        synthetic elastomer. Please indicate what these patterns are.

    c.  In Figure 3, three samples of the synthetic elastomer are shown.
        Is there any significance in showing three samples? If not, it
        is recommended that only one be shown. If there is, please
        indicate the significance.

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-   For comments 3-c, 3-d, and 3-e about Figure 3, the photograph is
    changed and the size of the synthetic elastomer is described in the
    figure caption.

    a.  How were results shown in Figures 2, 4, and 5 obtained? Please
        specify experimental method and equipment utilized to obtain
        these data before the data is presented.

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-   All the equipments for experiments and the sizes of specimens are
    described.

    a.  Figure 5 indicates VHB4905, which is a 0.5 mm thick VHB sheet.
        Is there any significance in mentioning this in Figure 5 but not
        in Figure 4? Please be consistent.

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-   Figure 4 is revised.

    a.  Section 4.1: "VHB series have higher values of
        ![](media/image5.wmf)..." Were different thicknesses of the VHB
        tested in calculating the dielectric constant? Which of the VHB
        series was used to obtain the dielectric constant? Does it
        matter?

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-   That sentence is corrected. Actually VHB4905 and VHB4910 are same
    material so the dielectric constant of two VHB must be same.

    a.  Section 4.1: Figure 2. What geometric actuator configuration was
        used to obtain the values of the dielectric constants? Strip?
        Circular? Please specify how the dielectric constant values were
        obtained and calculated.

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-   The measuring equipment and the geometry of specimen are described
    clearly.

    a.  Section 4.2: Please describe the size of the tensile specimens
        used to obtain the results shown in Figure 4.

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-   The size of specimens is mentioned.

    a.  Section 4.2: There seems to be an error in the callout of the
        stress levels in this section. Four stress values are given,
        however, only three types of materials are referenced. Please
        correct this error.

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-   The sentence is corrected.

    a.  Section 4.2: Please indicate the type of stress. Engineering
        stress? True stress?

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-   The "stress" is revised to "engineering stress".

5.  **Section 5**

    a.  (Section 5.1) The first two sentences are difficult to
        understand. It is not necessary to mention the inactive regions
        of the actuator because it is irrelevant to the topic of this
        section. The second sentence does not make sense. The words
        "impossible" and "difficult" are used. The usage of the word
        "difficult" implies that radial strains can be measured however
        it may be challenging. Impossible means that there is no means
        of measuring the radial strain. It is doubtful that this is the
        case. Furthermore, the inactive region of the circular actuator
        is the fixed boundary imposed by the rigid frame. Hence the
        radial strain at this boundary is zero. The radial strain can
        also be experimentally determined by using digital images of
        conical "V" shape of deformed actuator (as shown in Figure 6).

    b.  (Section 5.1) Describe how the synthetic elastomer is stretched
        onto the frame. Mention if the frame is rigid or not. I assume
        it is rigid.

    c.  (Section 5.1) Also, please indicate that you are assuming that
        the thickness is the same on the entire plane of the actuator
        upon prestretch, if any. Or that you are only considering the
        pole of the actuator.

-   For comments 5-a, 5-b, 5-c, and 5-f, the section 5.1, 5.4 and Fig. 6
    are revised clearly.

-   There are two different experiments in the section 5. The one is
    performed without prestrain on the specimens to measure deformation
    (section 5.2), response and hysteresis(section 5.3). The other is
    performed with prestrain to compare with other results (section
    5.4).

-   The prestrain on dielectric elastomer makes several negative and
    positive effects during actuation. So the experiments without
    prestrain are required to verify the actuation feature of material
    itself.

    a.  (Section 5.1) The terms "radial expansion" and "radial strain"
        are used interchangeably. Please be consistent and use only one
        of the term

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-   The terms are consistent with "radial expansion".

    a.  (Section 5.2) This section is titled 'displacement" however
        "radial strain" and "strain" is used in Figure 7 and Section 2,
        respectively. Please be consistent as the usage of these three
        terms hinders the clarity of this section.

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-   The terms are consistent with "radial expansion".

    a.  (Section 5.4) This section should be moved prior to Section 4.2
        or possibly in a section titled Experimental setup.

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-   The section title is changed to "Experiment with prestrain for
    comparisons of elastic energy".

\* Except the commented sentences and paragraphs, we corrected several
minor errors and typos in the paper.