Field-Dependent Stiffness of a Soft Structure Fabricated from Magnetic-Responsive Materials: Magnetorheological Elastomer and Fluid
Round 1
Reviewer 1 Report
The paper concerns the fabricatin and testing of a magneto responsive composite structure in which the ferro particles are not only in the rubber skin but also in liquid cavities. The work is interesting and relevant for the journal.
I still have a few questions and remarks:
The measure stiffness increase is in length direction but for practical use it is also important to know how much also the bending stiffness and stiffness in thickness direction increase (e.g. important for the keyboard example). Note that the particles are aligned in thickness (Fig.11). Please discuss. In Fig.6 the authors mentioned isotropic curing. Could it be that isothermal is meant? Figure 8a is not clear. Where are the permanent magnets with respect to the sample. Maybe a white background in the tensile tester can help. Table 1+2 take almost 1 page of the paper whereas it just contains fit functions to the graphs in Fig.10. Maybe better remove that from the paper and put it as supplementary information In fig.13 it is not clear where the liquid metal core is
Author Response
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Author Response.pdf
Reviewer 2 Report
The article presents a very interesting idea to produce a composite based on MRE and MRF to create a material with properties controlled by an external magnetic field. The geometry of the analyzed structure was presented, as well as materials used, the method of production and the procedure for testing the obtained structure were also described. The tested sample is analyzed in terms of stiffness change depending on the value of the set external magnetic field.
The article is correctly edited, the research methods are described as well as the conclusions. There are, however, several details which I would like to discuss.
Page 4, line 119 “…solid state, which distinguishes MRF which is fluid state in the absence of the magnetic field.” – I am not sure about the sense of this sentence. Shouldn’t it be “differs from” instead of distinguishes Page 4 line 134 “…because it is easier to product than the anisotropic MRE” – I think it should be “produce” instead of “product” Figure 3 and Figure 4 – It is not clear where does the data come from. Have the authors tested the shear modulus and Yield stress by themselves or it is just presenting the manufacturers’ data. It should be clearly stated. If the authors performed the experiment there should be some information about it. Furthermore, there is a Legend on both plots describing the red line as ‘regressed’. Is it the red line a regression curve or just fitting curve? If it is really regression, what was the formula for the regression model? Page 6 – additional information on the production process could be useful, in particular, I mean the temperature at each stage. Page 8 – I don’t think it makes any sense to include numerical result of FEM analysis in this paper if you use experimental data anyways. I think this information, as well as figures 8d-e, are redundant. Page 11 – There are results presented for magnetic flux density 0T, 0.1T, 0.2T and 0.3T. It seems there is very little influence below 0.1T In fact, we see that the behavior of the structure changes significantly for higher values of mean magnetic flux density. I think it would be great to include some additional results for higher values (greater than 0.3) or at least some additional results from the range 0.1T-0.3T so the relation was easier to be observed. In the context of research and mechanical properties of intelligent composites, in particular those using MRE, the following work was also created that is worth mentioning: Materials 2017, 10(12), 1359; https://doi.org/10.3390/ma10121359
Author Response
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Reviewer 3 Report
In this manuscript, a new soft structure whose stiffness can be tuned by external magnetic stimuli is fabricated from two different magnetic-responsive materials: magnetorheological elastomer (MRE) as a skin layer and magnetorheological fluid (MRF) as a core to be filled in void channels of the skin layer. The results indicate that the sample with MRF exhibits much higher stiffness increment than that of the sample without MRF under same conditions. The design of the field-dependent soft structure is innovative, and the fabrication method is facile and cost-effective. This research work and the results may be interested by broad range of readers. After careful consideration, the manuscript is recommended for publishing in the journal Materials after minor revision. Following are some specific comments:
Two conceptual applications of a haptic rollable keyboard and a smart braille watch are presented in the manuscript. However, there are no experimental validation in this study. Please give a proof-of-concept study in the revised manuscript. Does the as-prepared soft structure show anisotropic stiffness under the magnetic field? The stiffness of the soft structure perpendicular and parallel to the magnetic field should be investigated and compared.
Author Response
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