Practical Formulation Science for Particle-Based Inks

Round 1

Reviewer 1 Report

A very interesting pragmatic article trying to bridge the gap between application and fundamental research.

General comments

A very timely and useful discussion paper – with a great philosophy of bridging the gap between basic and applied science. It is very well written, clear and in general concise.

It may seem trivial to the author and the reader can go and find the equations used but I feel the article would be more complete to have the equations related to each App somewhere…in an SI or on the graph of the app or as for traditional papers in the text. Otherwise the reader gets the feeling that these are imprecise apps…even if they are more qualitative than quantitative the equations will help clarify the approach. i.e. choosing the right theory for the right problem. A lot of this comes down to experience which the author has in plenty and luckily for us is happy to share it with the scientific community.

One minor criticism is that other available apps – even if they are perhaps not as user friendly as some of those presented by the author - could also be mentioned such as the Materials cloud platform [1] (e.g. ShiftML: A machine learning model to predict the isotropic chemical shielding of molecular crystals containing H, C, N and O, and an interactive 3D visualiser.) and other freeware (e.g. HAMAKER released in 2012 for DLVO based (including steric repulsion) colloidal stability modelling [2]).

I also think the use of statistically designed experiments can help people move from a local minimum where they never find the true optimum or global minimum for a formulation – naturally as the author points out based on some scientific physical basis and not just a fitting of experimental data to give an empirical formula.

Maybe the title needs a more explicit form – e.g.

Towards better practical formulation science for particle-based inks – from DLVO theory through rheology to Hansen Solubility (compatibility) indexes. …….

I am not sure if it is so quite straightforward to produce apps with good science and lines 84 87 – but the sentiment is understood …the user needs to be convinced that the approach is solid and well based, and this type of article will help.

In fact I am trying to “appify” the good science that comes out of my institute at the moment and fully agree with the main message of the paper – most people don’t carry out quality science and are not capable of using up to date theories and “appifying” them themselves…this is a great need for the scientific and industrial community as a whole. I shall use the paper to try and promote the philosophy – in fact I am doubly enthusiastic about the idea after reviewing this paper. So I would like to sincerely thank the author for his efforts.

 

Detailed comments

Lines 121 – 125 – I find the comments on zeta potential a little frivolous. Yes it is a difficult concept and full of pitfalls but a more scientific explanation of the difficulties are needed – e.g. the limits generally accepted are the zeta plane is situated between the Stern layer (0.5nm) and the electrical double layer thickness (function of ionic make-up and strength of the aqueous solution) – [3,4]r. In some situations, even the charge model is needed to correctly use the DLVO theory [5]

Lines 196 197…not a very well constructed sentence I had to read it 3 times to see what was the fiction part. I suggest “characterized by a linear relationship with a wavelength lambda in a coating of…” maybe even put in both equations….the fiction and Orchard equations.

Line 220 – equation for spreading…please

Line 240 – equation and definition of Maragoni number needed…

Fig 7. Axes on graphs not really visible unless blown up …a quick fix possible?

Fig 8. I understand the authors’ frustration with the many ways of approximating a yield stress and it does seem to be field (food, cement, ceramics, paint) and magnitude dependent but maybe he can choose 2 simple methods as suggestions for simplification for readers who are expert. E.g. i) the G (prime) G(double prime) and ii)  shear stress shear rate – linear Bingham as a place to start.

Line 326…does the Conclusion mean, the conclusions of the current article?

Figure 10 – equations used please…..

Section 3.2.3 Particle solubility

The discussion is very interesting and the example clear but the figure 11 is not so easy to follow…it needs to be “manipulated” with labels of the polymer and nanoparticle and the two poor solvents and the useable mixture to help the reader …going to the app which only reproduces the images in the figure is not a useful an option in a printed paper.

I think the use of the word solubility for people working with sparingly soluble inorganic materials is the thing that frightens them away…I understand that the polymer/pharmaceutical end of the spectrum more easily accept the arguments. I think calling it Hansen bonding indexes or Hansen compatibility indexes would help conquer the inorganic particulate community….i.e. in the app give a little explanation on why it was traditionally called solubility but really is a compatibility index.

In fact the approach is very similar to Gordy’s hydrogen bond index (HBI) approach [6], the Hilderbrand solubility parameter [7] and the hydrophobic and lyophobic bonding (HLB) approach [8] as well as dielectric constant matching [9]which has been used to discern if a solvent (or even mixer of solvents) can wet and disperse a solid[10]. All of which are old industrial approaches which have been perhaps laid aside, similar to the Hansen index. The use of Apps as proposed in this paper is a great way if re-introducing these ideas to the modern generation of scientists.

Line 466 – I think the word useless is too harsh…unhelpful would be my description  - in that there are people in the scientific community who do benefit form theoretical advances despite their sometimes inherent complexity.

I support the need for low to high shear theory need and in fact, I am reviewing another paper, which I feel has made significant progress in this area and will get the paper to the author once both this paper and the other have been published.

References

[1] www.materialscloud.org

[2] U. Aschauer, et al, J Dispersion Science Technology. 32(4), 470 – 479 (2011

[3] F. J. Montes Ruiz-Cabello, G. Trefalt, Z. Csendes, P. Sinha, T. Oncsik,  I. Szilagyi, P. Maroni, M. Borkovec, J. Phys. Chem. B 2013, 117, 11853−11862    

[4] H. Li et al. / Journal of Colloid and Interface Science 258 (2003) 40–44

[5] F. J.Montes Ruiz-Cabello, P. Maroni, and M. Borkovec. J.CHEM.PHYS. 138, 234705 (2013)

[6] F.M. Fowkes, Rubber.Chem.Technol. 57, 328-344, (1984)

[7] H. Burnell, Off. Dig., Fed. Soc. Paint Technol. 29, 1069-1076 (1957)

[8] E.P. Liemerman, Off. Dig., Fed. Soc. Paint Technol., 34 30 (1962)

[9] T.A. Ring, p.374 , Fundamentals of ceramic Powder Processing and Synthesis, Academic Press, San Diego, 1996.

[10] C. Bernhardt, Adv. Colloid. Interface. Sci. 29, 79-139, (1988)

Author Response

Response is attached

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper investigates the limitations and opportunities associated with particle-based ink formulation. The paper is timely in the advent of significant innovation in slot die, spray, ink-jet, and extrusion printing technologies. The paper is a good resource. The paper could be strengthened with the following recommendations:

) Appification should be defined clearly

) A table of apps in this area of interest should be tabulated/summarized in supporting information.

)Figure 7 extends outside margins, and axis are challenging to read

) The paper discusses a hansen similarity parameters as a away to describers stabilizers (i.e. polymer). Typically steric hindrance can be introduced using an extended DLVO theory. An assessment of this model would be valuable for this paper.

) More details regarding simulation of rheology would be of valuable.

The paper is interesting and presents a potentially interesting application. However, the paper lacks a rigorous scientific description of the relevant theory. 

Author Response

This paper investigates the limitations and opportunities associated with particle-based ink formulation. The paper is timely in the advent of significant innovation in slot die, spray, ink-jet, and extrusion printing technologies. The paper is a good resource. The paper could be strengthened with the following recommendations:

Thank you for the positive comments and the suggestions below

 

) Appification should be defined clearly

Done

) A table of apps in this area of interest should be tabulated/summarized in supporting information.

My view of the article is that the Supporting Information is provided by the apps themselves, so it seems not to add value to create extra S.I. However, I acknowledge (as per Reviewer 1) that I should have added more details within the article to improve the balance and I hope Reviewer 2 now finds the balance to be more acceptable

)Figure 7 extends outside margins, and axis are challenging to read

I have corrected the margins and, as Reviewer 1 also had trouble with the axes, I have expanded the text of the Figure text to better explain what is going on.

) The paper discusses a hansen similarity parameters as a away to describers stabilizers (i.e. polymer). Typically steric hindrance can be introduced using an extended DLVO theory. An assessment of this model would be valuable for this paper.

The steric stabilization is already fully described in the DLVO section and the accompanying app and specifically links the χ parameter used in the standard extended DLVO theory to the more readily accessible HSP Distance.

) More details regarding simulation of rheology would be of valuable.

Providing the details of all six yield stress curves and the 6 interconversions would require an entire paper in its own right. Indeed, the six yield stress curves are from a paper only on that topic and the interconversions are derived from 3 different resources. I have therefore added a sentence to point out that all relevant formulae or academic references can be found in the apps.

The paper is interesting and presents a potentially interesting application. However, the paper lacks a rigorous scientific description of the relevant theory.

In general, the rigour is provided within the text of the apps themselves (and, where necessary, in my free eBooks). The point of the article is not so much the individual examples (I have ~300 apps on my site, many of which are relevant to the printing world) but that great science (none of which is my own) should be routinely made available to those for whom it is said that the work is being done.

 

 

Round 2

Reviewer 2 Report

The authors have addressed all my concerns and the paper represents a good resource for engineering particle inks. This is a growing area, and thus this paper will be of value to the community.