The multidisciplinary interplay in materials sciences: can we understand and mimic the nature?

Nature is smart and brilliant. In nature, we can find the best examples on how to biosynthesise a material and use it for several purposes with efficiency. An astonishing case study is the spider silk which is a form protein fibre structurally similar to cellulose and human hair. Looking at the nanoscale, Transmission Electron Microscopy (TEM) analysis performed by Simmons et al. [1] has revealed an intriguing microstructure without any resemblance with typical man’s made materials: the spider silk is composed of small crystallites with sizes around of 30 nm separated by amorphous regions cross-linking those nanocrystals.

This semi-crystalline microstructure is responsible to deliver a unique set of properties which express the complexity and the beauty of such spider fibres. The tensile strength, 1.30 GPa, is in the order of the stainless steels, 1.65 GPa, with its density corresponding to a sixth of the steels [2]. With extreme ductility, these fibres can be stretched almost up to six times of their unloaded length. In terms of structural integrity, the mechanical properties of the spider silks are hold within the temperature range of -40 to 220°C, unlikely relevant for the natural environments. Darwin’s bark spider silk can reach up to 520 MJ/m³ of toughness: at around 10 times higher than Kevlar toughness [3].

Are the metallurgists and material scientists able to invent a material inspired by the semi-crystalline spider silk microstructure and make use of its properties? An interesting multidisciplinary field that, nowadays, has attracted the attention of the scientific community is known as biomimetics.  Consists in how scientists can interpret nature aiming at the design and synthesis of materials and structures by means of mimicking biological process.

In material sciences, the benefits of adopting an interdisciplinary biomimetic approach could bring enormous consequences to the next generation of researchers and engineers. The simple fact that a biological spider silk with mixed amorphous-crystalline microstructure can give birth to a protein-based material with comparable mechanical strength of the human top-steels is an astonishing achievement.

As pointed out in this blog before, superspecialisation has created an entire generation of professionals without any commitment with nature, environment and wellbeing. We need to go back to our roots. To observe nature as scientists and learn with it. To extract the best that nature can give us, and as a result, produce bio-inspired materials with enhanced properties. The triad metals-ceramics-polymers is old fashion and may condemn the creativity of our students for their entire carrers.

[1] SIMMONS, Alexandra H.; MICHAL, Carl A.; JELINSKI, Lynn W. Molecular orientation and two-component nature of the crystalline fraction of spider dragline silk. SCIENCE, p. 84-87, 1996.

[2] SHAO, Zhengzhong; VOLLRATH, Fritz. Suprising strength of silkworm silk. NATURE, 418, 741, 2002.

[3] BLACKLEDGE, Todd; KUNTNER, Matjaz; AGNARSSON, Ingi. Bioprospecting finds the toughest biological material: extraordinary silk from a giant riverine orb spider. Plos one, v. 5, n. 9, p. 1, 2010.

Featured Image: Darwin’s back spider. Credits: BBC London.

How to get rid of pseudoscience?

This post is the English translation of my post “Como se livrar da pseudociência”, published in Portuguese here.

Some months ago I read a post which started like this “Studies show that any post which starts with studies show will be taken seriously by the reader”. This is, of course, a joke (or better, a metajoke), but it is, in some sense also true.

We are flooded with information from multiple sources. Only in Facebook there is a multitude of “so said” science channels. Due to the anarchist nature of internet, anyone can create one of these pages or even a science blog (no pun intended). Worse than that, everyone competes for attention.

Dealing with science one should expect honesty and knowledge of the subject by the ones who create these channels. Unfortunately this is not always the case. In the nonsense search for audience these channels share questionable posts, either by ignorance (in the sense of lack of knowledge) or by ill intention. This is one of the sources of pseudoscience.

There is, however, another source of pseudoscience: ideology driven channels. Fundamentalist religious groups and adepts of conspiracy theories use the internet to gather followers. Ideology and science never worked well together, the ability to question the results is an integral part of the scientific method and this kind of fanatic is unable to proceed with this questioning, so what they generate is always pseudoscience.

But what about the reader? How can he (or she) protect from (or even recognize) pseudoscience? After all, not everybody interested in science has the capability to understand the details and particularities of the scientific method. Also, many of my colleagues refuse to educate the general population and, particularly n Brazil, the poorness of science teaching in the fundamental and intermediate education levels create the proper ground for spreading pseudoscience.

Here are some clues to recognize pseudoscience:

  1. Be suspicious of bombastic contents. Once I read a post which claimed the disk of planet Mars would appear in the sky with the same size as the Moon, this is obviously ridiculously impossible.
  2. Due scientific results are usually published in trustworthy sources: scientific magazines and pages maintained by important universities and research institutes. Published articles usually go through the peer reviewing, a process in which other scientists (usually anonymous) evaluate the work before publishing (but attention, really revolutionary results are usually published in repositories first, therefore before peer reviewing, this does not mean they are less trustworthy). It is always important to read the original source (if possible), the authors of the articles not always understand what they read.
  3. Trust in the science you learned. It is true that really revolutionary results may challenge the view we have from reality at any moment, but Newton’s third law, mass and energy conservation, and the basic chemical reactions in biological organisms will not cease to exist from one day to the other.
  4. True science admits the contradictory, so, get suspicious of any post which claims to defend the absolute truth, without questioning the own result.

I hope this helps.

 

 

What makes a materials scientist tickle?

Back in year 1996 Walter Schütz, in his work “A history of fatigue” told the history on how Gassner in 1941, measuring the fatigue strength of high strength aluminum alloys of the series 7XXX (Al-Zn-Mg), and finding this was not much different from the lower strength, lower cost, alloys of series 2XXX (Al – Cu), warned that if they were used, for example, to build an airplane, this would lead to premature fatigue failures.

This argument is tricky  and seems illogical. Aren’t the alloys of series 7XXX of higher strength compared to alloys 2XXX? And didn’t Gassner find out the fatigue strength was about the same? So why would the fatigue live be smaller if the 7XXX alloys were used?

The explanation for this apparent contradiction is simple. The only possible reason to use a higher strength alloy (especially when it is more expensive) in place of a lower strength one, is to allow higher static stresses. In practice, one is able to reduceaviao-comercial-embraer-175-1334930067222_956x500 the thickness of a sheet, used to build, for example, the fuselage of an airplane. This leads to a lower mass of the structure, which is a good thing for airplanes. The loads acting on the structure, however, are approximately unchanged, since they depend mostly on the overall geometry of the structure. Since stress is the load divided by the cross section area, the material will work at a higher static strength level, and hence this will be inversely proportional to the thickness .

The problem is that the dynamic load (for example, the maximum and the minimum loads in function of time) are also inversely proportional to the reduction in thickness, therefore the difference between the maximum and the minimum stresses, in other words, the stress amplitude will also increase proportionally, leading to a more severe fatigue loading. Therefore fatigue life will be shorter, not because the fatigue strength (the material’s property) decreased, but because the loading became more severe, surpassing the fatigue strength.

This kind of elaborate argument is typical in Materials Science, a similar argument justifies why quenched steels should not be used in the maximum hardness is subject to a hydrogen-rich environment.  Another tricky argument explains also why low stacking fault energy FCC metals present higher strain hardening.

I call this non-linear thinking. A present cause results in an effect as a consequence of a long chain of events, which is not self-evident in principle. As I already wrote, in my opinion the aim of superior education is to prepare the student for this way of thinking.

Non-linear thinking, however, is very common in Materials Science. I believe this is due to the highly interdisciplinary  character of this subject. Of course, other scientific branches are also characterized by interdisciplinarity, but this seems to be more common in Materials Science.

It is this particular way of thinking which motivates the materials scientist. Non-linear thinking is addictive, the first time you get confronted, and understands, one of these long elaborate logical arguments, you will feel the need to learn more of the kind. So, be warned, if you are satisfied with thinking on thing in short cause-effect terms, stay away from Materials Science.

Hydrogen Embrittlement Topic – Special Symposium ICF14 Conference, Rhodes, Greece, June 18-23, 2017, “Fatigue and fracture in aggressive environments: mechanisms and risk assessment”

Recommended.

Hydrogen Embrittlement & Materials Science

Dear colleagues,

14th International Conference on Fracture (ICF14) will be held in the island of
Rhodes (Greece, June 18-23, 2017). For more information about ICF14
please, log on to the conference web page http://www.icf14.org

Prof. Emmanuel Gdoutos, Conference Chairman asked Prof. Robert Akid
(University of Manchester), Prof. Ihor Dmytrakh (Karpenko Physico-Mechanical Institute of National Academy of Sciences of Ukraine) and meas the members of the Scientific Advisory Board of ICF14 to organize the special symposium/sessions titled:

“Fatigue and fracture in aggressive environments: mechanisms and risk
assessment” 

within the frame of the Conference Programme.

LOGO

We plan that this special symposium will cover the many important and actual
aspects of a general problem “Environmentally Assisted Fracture” including the following three main topic areas:
1. Stress Corrosion Cracking,
2. Corrosion Fatigue and
3. Hydrogen Embrittlement.

Our aim is to bring together top scientists and researchers in the field of  environmentally assisted fracture and hydrogen embrittlement in order to present the lastest achievements in fatigue and fracture in aggressive environments research and the current state of the art in understanding of hydrogen embrittlement phenomena.

We kindly invite you and your colleagues to participation in
this event. Please feel free to submit your Abstracts online before October 30, 2016.

We are looking forward to hearing from you and working closely with
you for the organization of a successful symposium.

Important Conference Dates:
– Second Announcement: December, 2015
– Submission of Abstracts: October 30, 2016
– Notification of Acceptance/Rejection: December, 2016
– Conference: June, 2017

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Materials Matter!

I had the honor and privilege to know Wole Soboyejo, from Princeton. He presented a seminar at the Materials Science and Engineering Department at Texas A&M University where I’m staying this week. During his talk he explained how he was moved by a question his mother (a biologist) stated after he explained the important thins he did for aerospace engineering: “what does this mater for ordinary people?”. He explained how this question directed his later career development. What I found more interesting was the way in which he addressed the young audience, showing how the basic knowledge in Thermodynamics, Fracture Mechanics, helps him in seeking solution to problems like early detection of cancer cells, or increasing the life of OLEDs, or solving the problem of furnishing clean water to the poorest of the poorests. Later I had the opportunity to have a dinner with him, invited by Prof. Alan Needleman, his wife Wanda, Prof. Ibrahim Karaman and Prof. Raymundo Arróyave. It was a pleasant night and I could only confirm the first impression I had, he is a remarkable human being. The whole Department of Materials Science and Engineering in the Texas A&M University also impresses me in good sense. It shows all characteristics of an exciting work ambient.

News about the mechanism of interaction between neurons and Zika virus

Researchers in Brazil mobilized to try to understand the correlation between Zika infection in pregnant women and the development of microcephaly in the babies. Now first reports indicate that the virus attacks preferentially neuron precursor cells inside the uterus. I am not biologist, but it seems that the study used some pretty sophisticated in vitro techniques to obtain these results. This case is an important demonstrations of the correlation between applied and fundamental research. The case has an obvious importance for public health not only in Brazil, but also for the whole world, but it was only possible because someone in the past investigated these neuronal precursors cells and developed the techniques which are used in the study.  As I already mentioned before, I prefer to call this kind of research “useful research”, instead of applied (or fundamental). These two terms sell the idea that these kinds or researches can be disconnected.