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Lagerwall J.P.F.,Korea Advanced Institute of Science and Technology | Lagerwall J.P.F.,Advanced Institute of Convergence Technologies | Schutz C.,University of Stockholm | Schutz C.,Wallenberg Wood Science Center | And 7 more authors.
NPG Asia Materials | Year: 2014

Cellulose nanocrystals (CNCs), produced by the acid hydrolysis of wood, cotton or other cellulose-rich sources, constitute a renewable nanosized raw material with a broad range of envisaged uses: for example, in composites, cosmetics and medical devices. The intriguing ability of CNCs to self-organize into a chiral nematic (cholesteric) liquid crystal phase with a helical arrangement has attracted significant interest, resulting in much research effort, as this arrangement gives dried CNC films a photonic band gap. The films thus acquire attractive optical properties, creating possibilities for use in applications such as security papers and mirrorless lasing. In this critical review, we discuss the sensitive balance between glass formation and liquid crystal self-assembly that governs the formation of the desired helical structure. We show that several as yet unclarified observations - some constituting severe obstacles for applications of CNCs - may result from competition between the two phenomena. Moreover, by comparison with the corresponding self-assembly processes of other rod-like nanoparticles, for example, carbon nanotubes and fd virus particles, we outline how further liquid crystal ordering phenomena may be expected from CNCs if the suspension parameters can be better controlled. Alternative interpretations of some unexpected phenomena are provided, and topics for future research are identified, as are new potential application strategies. © 2014 Nature Publishing Group. Source

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Athletes, the elderly, and others who suffer from injuries and arthritis can lose cartilage and experience a lot of pain. Researchers are now reporting, however, that they have found a way to produce cartilage tissue by 3D bioprinting an ink containing human cells, and they have successfully tested it in an in vivo mouse model. The development could one day lead to precisely printed implants to heal damaged noses, ears, and knees. “Three-dimensional bioprinting is a disruptive technology and is expected to revolutionize tissue engineering and regenerative medicine,” says Paul Gatenholm, Ph.D. “Our team’s interest is in working with plastic surgeons to create cartilage to repair damage from injuries or cancer. We work with the ear and the nose, which are parts of the body that surgeons today have a hard time repairing. But hopefully, they’ll one day be able to fix them with a 3D printer and a bioink made out of a patient’s own cells.” Gatenholm’s team at the Wallenberg Wood Science Center in Sweden is tackling this challenge step by step. First, they had to develop an ink with living human cells that would keep its shape after printing. Previously, printed materials would collapse into an amorphous pile. To create a new bioink, Gatenholm’s team mixed polysaccharides from brown algae and tiny cellulose fibrils from wood or made by bacteria, as well as human chondrocytes, which are cells that build up cartilage. Using this mixture, the researchers were able to print living cells in a specific architecture, such as an ear shape, that maintained its form even after printing. The printed cells also produced cartilage in a laboratory dish. “But under in vitro conditions, we have to change the nutrient-filled liquid that the material sits in every other day and add growth factors,” Gatenholm says. “It’s a very artificial environment.” So the next step was to move the research from a lab dish to a living system. Gatenholm’s team printed tissue samples and implanted them in mice. The cells survived and produced cartilage. Then, to boost the number of cells, which is another hurdle in tissue engineering, the researchers mixed the chondrocytes with human mesenchymal stem cells from bone marrow. Previous research has indicated that stem cells spur primary cells to proliferate more than they would alone. Preliminary data from in vivo testing over 60 days show the combination does indeed encourage chondrocyte and cartilage production. Gatenholm says further preclinical work needs to be done before moving on to human trials. To ensure the most direct route, he is working with a plastic surgeon to anticipate and address practical and regulatory issues. In addition to cartilage printing, Gatenholm’s team is working with a cosmetic company to develop 3D bioprinted human skin. Cosmetic companies are now prohibited in Europe from testing cosmetics on animals, so they hope to use printed skin to try out makeup, anti-wrinkling techniques and strategies to prevent sun damage. He acknowledges funding from the Knut and Alice Wallenberg Foundation, Eurostar/Vinnova, and the Västra Götalands Regionen.

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Site: http://www.nanotech-now.com/

Home > Press > Transparent wood could one day help brighten homes and buildings Abstract: When it comes to indoor lighting, nothing beats the sun's rays streaming in through windows. Soon, that natural light could be shining through walls, too. Scientists have developed transparent wood that could be used in building materials and could help home and building owners save money on their artificial lighting costs. Their material, reported in ACS' journal Biomacromolecules, also could find application in solar cell windows. Homeowners often search for ways to brighten up their living space. They opt for light-colored paints, mirrors and lots of lamps and ceiling lights. But if the walls themselves were transparent, this would reduce the need for artificial lighting — and the associated energy costs. Recent work on making transparent paper from wood has led to the potential for making similar but stronger materials. Lars Berglund and colleagues wanted to pursue this possibility. The researchers removed lignin from samples of commercial balsa wood. Lignin is a structural polymer in plants that blocks 80 to 95 percent of light from passing through. But the resulting material was still not transparent due to light scattering within it. To allow light to pass through the wood more directly, the researchers incorporated acrylic, often known as Plexiglass. The researchers could see through the resulting material, which was twice as strong as Plexiglass. Although the wood isn't as crystal clear as glass, its haziness provides a possible advantage for solar cells. Specifically, because the material still traps some light, it could be used to boost the efficiency of these cells, the scientists note. The authors acknowledge funding from the Knut and Alice Wallenberg Foundation. About American Chemical Society The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With nearly 157,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio. For more information, please click Contacts: Michael Bernstein 202-872-6042 Katie Cottingham, Ph.D. 301-775-8455 Lars Berglund, Ph.D. Wallenberg Wood Science Center Department of Fiber and Polymer Technology KTH Royal Institute of Technology Stockholm, Sweden If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Eita M.,KTH Royal Institute of Technology | Wagberg L.,KTH Royal Institute of Technology | Wagberg L.,Wallenberg Wood Science Center | Muhammed M.,KTH Royal Institute of Technology
Journal of Physical Chemistry C | Year: 2012

The incorporation of nanoparticles into polyelectrolytes thin films opens the way to a broad range of applications depending on the functionality of the nanoparticles. In this work, thin films of ZnO nanoparticles and poly(acrylic acid) (PAA) were built up using the layer-by-layer technique. The thickness of a 20-bilayer film is about 120 nm with a surface roughness of 22.9 nm as measured by atomic force microscopy (AFM). Thin ZnO/PAA films block UV radiation starting at a wavelength of 361 nm due to absorption by ZnO although the films are highly transparent. Due to their high porosity, these thin films show a broadband antireflection in the visible region, and thus they provide selective opacity in the UV region and enhanced transmittance in the visible region up to the near-infrared region. They are also superhydrophilic due to their high porosity and surface roughness. © 2012 American Chemical Society. Source

Karabulut E.,KTH Royal Institute of Technology | Pettersson T.,KTH Royal Institute of Technology | Ankerfors M.,Innventia Ab | Wagberg L.,KTH Royal Institute of Technology | Wagberg L.,Wallenberg Wood Science Center
ACS Nano | Year: 2012

The preparation of multifunctional films and coatings from sustainable, low-cost raw materials has attracted considerable interest during the past decade. In this respect, cellulose-based products possess great promise due not only to the availability of large amounts of cellulose in nature but also to the new classes of nanosized and well-characterized building blocks of cellulose being prepared from trees or annual plants. However, to fully utilize the inherent properties of these nanomaterials, facile and also sustainable preparation routes are needed. In this work, bioinspired hybrid conjugates of carboxymethylated cellulose nanofibrils (CNFC) and dopamine (DOPA) have been prepared and layer-by-layer (LbL) films of these modified nanofibrils have been built up in combination with a branched polyelectrolyte, polyethyleneimine (PEI), to obtain robust, adhesive, and wet-stable nanocoatings on solid surfaces. It is shown that the chemical functionalization of CNFCs with DOPA molecules alters their conventional properties both in liquid dispersion and at the interface and also influences the LbL film formation by reducing the electrostatic interaction. Although the CNFC-DOPA conjugates show a lower colloidal stability in aqueous dispersions due to charge suppression, it was possible to prepare the LbL films through the consecutive deposition of the building blocks. Adhesive forces between multilayer films prepared using chemically functionalized CNFCs and a silica probe are much stronger in the presence of Fe 3+ than those between a multilayer film prepared from unmodified nanofibrils and a silica probe. The present work demonstrates a facile way to prepare chemically functionalized cellulose nanofibrils whereby more extended applications can produce novel cellulose-based materials with different functionalities. © 2012 American Chemical Society. Source

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