Tag Archives: Sinan Keten

Cellulose nanocrystals and a computational approach to new materials

There’s been a lot of research into cellulose nanomaterials as scientists work to develop applications for cellulose nanocrystals (CNC)* and cellulose nanofibrils (CNF). To date, there have been no such breakthroughs or, as they used to say, no such ‘killer apps’. An Oct. 2, 2015 news item on Nanowerk highlights work which made finally lead the way,

Theoretically, nanocellulose could be the next hot supermaterial.

A class of biological materials found within numerous natural systems, most notably trees, cellulose nanocrystals have captured researchers’ attention for their extreme strength, toughness, light weight, and elasticity. The materials are so strong and tough, in fact, that many people think they could replace Kevlar in ballistic vests and combat helmets for military. Unlike their source material (wood), cellulose nanocrystals are transparent, making them exciting candidates for protective eyewear, windows, or displays.

Although there is a lot of excitement around the idea of nanocellulose-based materials, the reality often falls flat.

“It’s difficult to make these theoretical properties materialize in experiments,” said Northwestern Engineering’s Sinan Keten. “Researchers will make composite materials with nanocellulose and find that they fall short of theory.”

Keten, an assistant professor of mechanical, civil, and environmental engineering at Northwestern University’s McCormick School of Engineering, and his team are bringing the world one step closer to a materials-by-design approach toward developing nanocomposites with cellulose. They have developed a novel, multi-scale computational framework that explains why these experiments do not produce the ideal material and proposes solutions for fixing these shortcomings, specifically by modifying the surface chemistry of cellulose nanocrystals to achieve greater hydrogen bonding with polymers.

An Oct. 2, 2015 (McCormick School of Engineering) Northwestern University news release (also on EurekAlert), which originated the news item, provides more context for the research before describing a new technique for better understanding the materials,

Found within the cellular walls of wood, cellulose nanocrystals are an ideal candidate for polymer nanocomposites — materials where a synthetic polymer matrix is embedded with nanoscale filler particles. Nanocomposites are commonly made synthetic fillers, such as silica, clay, or carbon black, and are used in a myriad of applications ranging from tires to biomaterials.

“Cellulose nanocrystals are an attractive alternative because they are naturally bioavailable, renewable, nontoxic, and relatively inexpensive,” Keten said. “And they can be easily extracted from wood pulp byproducts from the paper industry.”

Problems arise, however, when researchers try to combine the nanocellulose filler particles with the polymer matrix. The field has lacked an understanding of how the amount of filler affects the composite’s overall properties as well as the nature of the nanoscale interactions between the matrix and the filler.

Keten’s solution improves this understanding by focusing on the length scales of the materials rather than the nature of the materials themselves. By understanding what factors influence properties on the atomic scale, his computational approach can predict the nanocomposite’s properties as it scales up in size — with a minimal need for experimentation.

“Rather than just producing a material and then testing it to see what its properties are, we instead strategically tune design parameters in order to develop materials with a targeted property in mind,” Sinko said. “When you are equalizing music, you can turn knobs to adjust the bass, treble, etc. to produce a desired sound. In materials-by-design, we similarly can ‘turn the knobs’ of specific parameters to adjust the resulting properties.”

Here’s a link to and a citation for the paper,

Tuning Glass Transition in Polymer Nanocomposites with Functionalized Cellulose Nanocrystals through Nanoconfinement by Xin Qin, Wenjie Xia, Robert Sinko, and Sinan Keten. Nano Lett., Article ASAP
DOI: 10.1021/acs.nanolett.5b02588 Publication Date (Web): September 4, 2015

Copyright © 2015 American Chemical Society

This paper is open access.

*Cellulose nanocrystals (CNC) are also known as nancellulose crystals (NCC).

Canada Foundation for Innovation “World’s Best”?; Ping hoodie, clothing that networks socially; life protection clothing; getting spiders to weave building materials?; open access archive for nano papers

The headline for the news release on Marketwire (via the Canadian Science Policy site) is: Canada Foundation for Innovation(CFI) Practices is Called ‘World’s Best’. As it’s been a bit slow for news here I began wondering ‘which practices in which countries are being compared’? After reviewing the reports quickly, I can’t answer the question. There are no bibliographies in any of the three reports related to this KPMG study while the footnotes make reference only to other KPMG and Canadian studies. It was a bit of surprise, I was expecting to see reports from other countries and/or from international organizations and some insight into their analysis as comparing agencies in different countries can be complicated.

I’m not sure how they arrived at their conclusion although they provide some interesting data. From the Overall Evaluation report (p. 28 PDF, p. 24 print),

Exhibit [Table] 4.16 shows that, on average, there have been about 6.4 collaborations with end-users per PL/PU in the past year, three-quarters of which used the CFI projects as key resources, and about 10.2 collaborations per Department Head, about 70% of which using CFI projects in a significant way. For PLs/PUs, there are only small differences in use of CFI projects as a key resource by type of end-user, but Department Heads show more variation in the use of CFI project by type of user; it is unknown if this is significant.

Note that 64% of PL/PUs’ and 80% of Department Heads’ end-user collaborations, respectively, are with Canadian organizations; there is a significant international component (with OMS data suggesting that the CFI projects are a significant attractor for international organizations to collaborate [emphasis mine]).

It certainly seems laudable although I question whether you can conclude that the CFI is a significant international organization attractor by inference alone. Shouldn’t this be backed up with another instrument, such as a questionnaire for a survey/poll of the international organizations, asking why they are collaborating with Canadian scientists? I was not able to find any mention of such a survey or poll taking place.

From everything I hear, Canadians are excellent at academic science research and attracting researchers from around the world and because of our penchant for collaboration we (as they say) “punch above our weight.” I just wish this report did a better job of providing evidence for its assertions about the CFI’s ‘best practices’.

Ping hoodie

Thanks to Adrian Covert’s article on Fast Company, I found information about a prototype for a piece of wearable computing, the Ping hoodie. From Covert’s article,

The Ping clothing concept makes use of embedded electronics and haptics controlled by the Arduino Lilypad system, which transmits to your device (most likely a smartphone) using the Lylipad Xbee. This tech serves as the core interface between you and the information you need. If someone special is sending you a call or text, you can set the hoodie to vibrate in a specific manner, letting you know it’s them. Actions as simple as lifting or dropping the hood can be used to send status updates and messages on Facebook, with the potential to target certain groups of friends.

There’s more at Fast Company or you can check out electricfoxy where the designer, Jennifer Darmour has her site which is where I found this image,

Ping hoodie (wearable computing) designed by Jennifer Darmour at electricfoxy

Do go to Darmour’s site (although Fast Company offers a pretty good selection) if you want to see all the images including close ups of the fabric (don’t forget to scroll horizontally as well as vertically).

Clothing that protects your life

P2i, a company I’ve mentioned here before, has announced a ‘new’ revolutionary form of protective clothing. Actually, it sounds like an improvement rather than a revolutionary concept but maybe I’m getting jaded. From the news item on Nanowerk,

A revolutionary new generation of high-performance body armour, launched today, is lighter, more comfortable and more protective than any previous design, thanks to P2i’s liquid-repellent nano-coating technology.

The new G Tech Vest is a joint development between two world-class UK companies with very strong credentials for the life protection market: P2i, whose technology was originally developed to make soldiers’ protective clothing more effective against chemical attack; and Global Armour, which has been at the leading edge of product innovation in the armour industry for over 30 years.

The G Tech Vest employs brand-new lightweight materials, both in the physical armour itself (a closely-guarded trade secret) and the fabric that forms the armour into a garment. P2i’s technology reduces weight by avoiding the need for bulky durable water repellents and increases comfort by preserving the natural airflow and drape of the garment material.

I recently (April 15, 2010) made a comment about how modern soldiers are beginning to resemble medieval knights and this talk of armour certainly reinforces the impression.

Spiders weaving building materials?

Michael Berger at Nanowerk has written an in-depth article about spider silk and its possible application, amongst others, as a building material. He’s interviewed one of the authors (Markus J. Buehler) of a recent paper that lays out “… a framework for predicting the nanostructure of spider silk using atomistic principles.” More from the Spotlight article on Nanowerk,

In a paper published as the cover article in Applied Physics Letters on April 12, 2010 (“Atomistic model of the spider silk nanostructure”), [Sinan] Keten and Buehler demonstrate an innovative application of replica exchange molecular dynamics simulations on a key spider silk repeating sequence, resulting in the first atomistic level structure of spider silk.

More specifically, the MIT researchers found the formation of beta-sheet structures in poly-Ala rich parts of the structure, the presence of semi-extended GGX domains that form H-bonded 31 helix type structures and a complete lack of alpha-helical conformations in the molecular structures formed by the self-assembly of MaSp1 proteins. These results resolve controversies around the structure of the amorphous domains in silk, by illustrating for the first time that these semi-extended, well-oriented and more sparsely H-bonded structures that resemble 31 helices could be the molecular source of the large semi-crystalline fraction of silks and the so-called ‘pre-stretched’ configuration proposed for these domains.

Shy of reading the original research, which I likely wouldn’t understand easily, Berger’s article provides an excellent entry into the subject.

Open access archive for nano papers

My final item for today is about a project to give free access to papers on nanotechnology that they host and/or publish.  Hooray! It’s very frustrating to get stuck behind paywalls so I’m thrilled that there’s an agency offering free access. From the news item on Nanowerk,

The Nano Archive, the online open-access repository for nanoscience and nanotechnology, invites you to submit research papers to be published free online for users across the globe.

Submitted papers can include peer-reviewed articles, journal articles, review articles, conference and workshop papers, theses and dissertations, book chapters and sections, as well as multimedia and audio-visual materials. The Nano Archive also welcomes new, unpublished research results to be shared with the wider community.

The Nano Archive is part of the ICPC NanoNet project, funded by the EU under FP7. It brings together partners from the EU, Russia, India, China and Africa, and provides wider access to published nanoscience research and opportunities for collaboration between scientists in the EU and International Cooperation Partner Countries.

The Nano Archive currently hosts over 6000 papers. You can read more about the sponsoring agency, the ICPC (International Cooperation Partner Countries) NanoNet here. It has funding for four years and was started in 2008.