Daniel Zhu | Peer Review

Conference Paper | Driving Soft Robots with Low-Boiling Point Fluids

This paper describes an new method of providing pressure for pneumatic soft robots through heating low-boiling point fluids with a compliant heating mechanism. It also discusses some potential applications of this method as well as the benefits and limitations of this method.

Garrad, Martin, Gabor Soter, Andrew T. Conn, Helmut Hauser, and Jonathan Rossiter. “Driving Soft Robots with Low-Boiling Point Fluids.” In 2019 2nd IEEE International Conference on Soft Robotics (RoboSoft), 74–79, 2019. https://doi.org/10.1109/ROBOSOFT.2019.8722812.

Notes:

• During the introduction, the paper does well to establish the range of existing pneumatic actuation technologies and the need for for a niche and improvements their proposed system would occupy.
• The explanation of the thermodynamics of a LBPF elastomer actuator was slightly confusing to me and too a few rereads to understand. I think this is because the writers assume that some physical interactions are common knowledge and do not take the time to state the reasons behind some interactions.
• The explanation behind the relationship between the heating element, liquid volume, and container volume is largely well explained. The accompanying charts help explain the dynamics between heat applied and pressure well.
• One thing I was confused about was the mention of how serpentine patterns were used to avoid “asymmetrical heating from current fringing.” I did not know what current fringing meant at the time.
• One concern I had reading this section was how all the tests were conducted with fixed volume vessels. However, earlier in the paper, the author had mentioned that in practice, vessels may not be fixed due to the use of soft materials. While underlying assumptions may lead one to assume the change might be small enough to be negligible, I would have appreciated more explicit explanation.
• I appreciated the step by step walk through of the fabrication process and the notes on how some modifications might be necessary to ensure the LBPF actuator works most efficiently.

General Review Criteria

1. Originality. All papers must present original work.

The paper appears to present original work with sources cited indicating where the paper was drawing off of the previous work of other researchers.

2. Novelty. We welcome big idea and provocative papers, even if they may not be perfectly implemented. We also welcome papers that bring together different disciplines and approaches.

This paper proposes a new form of pneumatic actuation that builds on the previous work of others. While other papers had made use of low boiling point fluids in the past, the addition of a heating element as well as other modifications make the interaction novel.

3. Relevance. All papers must be relevant to the field.

The paper’s premise and result is relevant to the field of soft robotics. It proposes a new way of producing pneumatic actuation that is relevant to a niche in the field. Based on the paper’s conclusion, it should afford further improvement and capabilities in the field of soft robotics in the future.

4. Soundness. A paper needs to be technologically and/or methodologically sound based on the criteria generally used for that technology or method within a given field.

The paper’s methods of experiment and measurement seem to be sound. Details on methods of measurement and materials used are provided.

5. Technical detail. Please provide adequate details to indicate what was done, how the data were collected, sample size and characteristics, what type of robot was involved, etc. Authors should use correct terminology for their methods to avoid being evaluated against the incorrect set of criteria.

I believe the data were collected with the right procedures and with detailed terminology. The authors were careful to include detailed information accompanying all the procedures and experiments they conducted, including component names, amounts, and methods of measurement.

6. Accessibility. All papers must be written to be accessible for a broad, interdisciplinary/multidisciplinary audience.

While the paper is generally accessible through its step by step explanation of the physical processes behind how the mechanism operates, I occasionally found myself having to re-read a section because the article made the assumption I had background knowledge about some of the physical processes involved. While I was able to reason backward from the conclusion, which speaks to its accessibility, I think a slightly deeper explanation could make the article slightly more readable.

Referee Form

1. Do you have any conflict of interest in reviewing this paper? A “conflict of interest” is defined as follows:
   1. Ph.D. thesis advisor or advisee
   2. Postdoctoral advisor or advisee
   3. Collaborators or co-authors for the past 48 months
   4. Any other individual or institution with which the investigator has financial tiesYes/no. If yes, please disqualify yourself instead of proceeding. 

No

1. Expertise. Provide your expertise in the topic area of this paper.
   • 4 – Expert
   • 3 – Knowledgeable
   • 2 – Passing Knowledge
   • 1 – No KnowledgeSingle choice. 

2

2. Summary. Please summarize what you believe are the paper’s main contributions to the field of soft robotics.Please write a short paragraph. 

The paper proposes a new way of producing pneumatic actuation with far more flexibility and much less strain energy wise and in terms of safety. Based on the paper’s conclusion, it should afford further improvement and capabilities in the field of soft robotics in the future.

3. Strengths and Weaknesses. What are the main strengths and weaknesses of this work? Does the paper have strengths in originality and novelty?Please write a short paragraph. 

I think the paper’s strength is in the novelty of the mechanism it proposes and in how it fills a niche in the field. It is also strong in how it explains each process step by step and includes details of the process. A slight weakness this paper might have is that it might not take the extra step to explain a process that makes it more easily accessible

4. Soundness. Are the ideas, algorithms, results or studies technologically/methodologically sound?Please write a short paragraph arguing for the strengths and weaknesses of the work. 

I believe the paper is methodologically sound. The data were collected with the right procedures and with detailed terminology. The authors were careful to include detailed information accompanying all the procedures and experiments they conducted, including component names, amounts, and methods of measurement.

5. Related Work. Does the paper adequately describe related and prior work? Please write a sentence or short paragraph. 

The paper adequately describes previous work. In the introduction, it provides an overview of the options available in the field of pneumatic actuation for soft robotics. It draws from a number of papers to describe the techniques that are currently used as well as their strengths and weaknesses. It then uses that information to justify the approach the paper takes as well as the niche it intends to fill.

6. Presentation. Is the paper well organized, well written and clearly presented? Please write a sentence or short paragraph. 

I believe the paper is well written and presented. The ideas and thought process presented logically follow each other and are explained throughly and and clearly at each point in the paper. Although, I had to reread a few sections of the paper, the step by step explanation allowed me to deduce the thought process behind each step.

7. Suggestions. Do you have suggestions for improving this paper?Please write several paragraphs detailing specific points of the paper which merit reconsideration. Be sure to address the text, figures and tables, mathematics, and grammar and spelling. 

My suggestions for improving the paper are relatively minimal. In places the reasoning might have been improved slightly to make the paper more accessible. For example in this section discussing the mechanics behind low boiling point fluids, the authors write: “A consequence of using a fluid which is close to its boiling point is that the saturation vapour pressure will also be large. When such a fluid is injected into a sealed vessel, it will evaporate until the pressure inside the vessel reaches the saturation pressure. This places a fundamental limitation on the lifespan of pouch motor style actuators driven by low-boiling point fluid.” Because I did not know what saturation vapor pressure meant before reading the paper, I had difficulty understanding why this property limited the lifespan of the pouches. It was only by reading the following section that I was able to look back and understand what this section meant. While more readers more knowledgeable about the field may not have an issue, a brief explanation about saturation vapor pressure or how it affects pouch lifespan would have been appreciated.

Other than occasional instances like the one described above, the text, figures, and tables are clear in their labeling, context, and conclusions. The math, grammar, and spelling also appear to make sense.

8. Comments to Committee (Hidden from authors). Does the paper have enough originality and importance to merit publication? Is the paper relevant to the field? These comments will NOT be sent to the authors:Please write one or more paragraphs as needed to justify your review judgement. 

I believe this paper has enough originality and importance to merit publication. While previous papers had made use of low boiling point fluids in the past, the addition of a heating element as well as other modifications make the interaction novel. Additionally, the paper’s premise and result is relevant to the field of soft robotics. It proposes a new way of producing pneumatic actuation that is relevant to a niche in the field. Based on the paper’s conclusion, it should afford further improvement and capabilities in the field of soft robotics in the future.

1. Overall Rating. Provide your overall rating of the paper (5 is best)
   • 5 – Definite accept: I would argue strongly for accepting this paper.
   • 4 – Probably accept: I would argue for accepting this paper.
   • 3 – Borderline: Overall I would not argue for accepting this paper.
   • 2 – Probably reject: I would argue for rejecting this paper.
   • 1 – Definite reject: I would argue strongly for rejecting this paper.

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