Nano News: 03/10/15

Scientists have found a way to make the strongest spider silk fibers

Researchers from Universidad Politécnica de Madrid (UPM) have produced the strongest spider silk fiber so far. They used a technique that made popular the silk from Murcia in the 19th century. Given the good properties of this new material, this silk can be used for regenerative medicine. Following the same procedure used to fabricate the hijuela in Murcia two centuries ago, which is a strong thread from silkworm, researchers from the Center for Biomedical Technology (CTB) at Universidad Politécnica de Madrid (UPM) have found a way to successfully produce the strongest spider silk fibers up to now. This new fiber was called hijuela de araña and its diameter is significantly greater than the natural fiber maximizing the load that can withstand before it breaks. This new feature along with the interesting mechanical and biocompatibility properties of the spider silk make this new material a suitable application for regenerative medicine. Fracture surface of spider silk

Fracture surface of the spider silk. Throughout the 19th century, the region of Murcia specialized and was famous for the production of hijuela, a very strong thread from silkworm. The traditional process consisted on using an acid liquid medium, generally water and vinegar, and to deform the silk glands where worms produce the proteins in the mentioned liquid. The hijuela used to be very strong and was used for fishing and sutures. Now, researchers from the group of Advanced Structural Materials and Nanomaterials from the ETSI Caminos, Canales y Puertos Engineering and CTB at UPM, experts in biomaterials and their application to regenerative medicine, have used this technique to make the strongest spider silk fiber up to now, and they have named as hijuela de araña. This study has been recently published in the journal ("Spider silk gut: Development and characterization of a novel strong spider silk fiber"). Researchers extracted the silk glands of spiders of the species Nephila inaurata, native to southern Africa and Madagascar. By deforming these glands into an acid medium, researchers were able to obtain fibers with significantly larger diameters than the natural ones, and they were also able to optimize the conditions to maximize the strength of fibers. This work is part of a line research that aims to obtain silk-based biomaterials for biomedical applications. Silk is indeed a biomaterial with excellent mechanical properties and great strength and deformability. Besides, by using the available biotechnological techniques is possible, in principle, to obtain artificial silks with improved properties like the ability to facilitate cell adhesion for applications such as scaffolds for regeneration of damaged tissues. Working with hijuela de araña allowed researchers to gain better understanding of the procedures for obtaining these materials. Besides, the great cross section of the hijuela de araña means that it can support a much higher force than natural silk fiber. This property suggests that natural silk could be replaced in some biomedical applications, such as biomaterials for tissue engineering.

Optical microfibres light the way for brain-like computing

Computers that function like the human brain could soon become a reality thanks to new research using optical fibres made of speciality glass. The research, published in ("Amorphous Metal-Sulphide Microfibers Enable Photonic Synapses for Brain-Like Computing"), has the potential to allow faster and smarter optical computers capable of learning and evolving.

Chalcogenide glass sample Researchers from the Optoelectronics Research Centre (ORC) at the University of Southampton, UK, and Centre for Disruptive Photonic Technologies (CDPT) at the Nanyang Technological University (NTU), Singapore, have demonstrated how neural networks and synapses in the brain can be reproduced, with optical pulses as information carriers, using special fibres made from glasses that are sensitive to light, known as chalcogenides.

"The project, funded under Singapore's Agency for Science, Technology and Research (A*STAR) Advanced Optics in Engineering programme, was conducted within The Photonics Institute (TPI), a recently established dual institute between NTU and the ORC."

Co-author Professor Dan Hewak from the ORC, says: "Since the dawn of the computer age, scientists have sought ways to mimic the behaviour of the human brain, replacing neurons and our nervous system with electronic switches and memory. Now instead of electrons, light and optical fibres also show promise in achieving a brain-like computer. The cognitive functionality of central neurons underlies the adaptable nature and information processing capability of our brains."

In the last decade, neuromorphic computing research has advanced software and electronic hardware that mimic brain functions and signal protocols, aimed at improving the efficiency and adaptability of conventional computers. However, compared to our biological systems, today's computers are more than a million times less efficient. Simulating five seconds of brain activity takes 500 seconds and needs 1.4 MW of power, compared to the small number of calories burned by the human brain. Using conventional fibre drawing techniques, microfibers can be produced from chalcogenide (glasses based on sulphur) that possess a variety of broadband photoinduced effects, which allow the fibres to be switched on and off. This optical switching or light switching light, can be exploited for a variety of next generation computing applications capable of processing vast amounts of data in a much more energy-efficient manner. Co-author Dr Behrad Gholipour explains: "By going back to biological systems for inspiration and using mass-manufacturable photonic platforms, such as chalcogenide fibres, we can start to improve the speed and efficiency of conventional computing architectures, while introducing adaptability and learning into the next generation of devices." By exploiting the material properties of the chalcogenides fibres, the team led by Professor Cesare Soci at NTU have demonstrated a range of optical equivalents of brain functions. These include holding a neural resting state and simulating the changes in electrical activity in a nerve cell as it is stimulated. In the proposed optical version of this brain function, the changing properties of the glass act as the varying electrical activity in a nerve cell, and light provides the stimulus to change these properties. This enables switching of a light signal, which is the equivalent to a nerve cell firing. The research paves the way for scalable brain-like computing systems that enable 'photonic neurons' with ultrafast signal transmission speeds, higher bandwidth and lower power consumption than their biological and electronic counterparts. Professor Cesare Soci said: "This work implies that 'cognitive' photonic devices and networks can be effectively used to develop non-Boolean computing and decision-making paradigms that mimic brain functionalities and signal protocols, to overcome bandwidth and power bottlenecks of traditional data processing."

Hydrocarbon photocatalysts get in shape and go for gold

A combination of semiconductor catalysts, optimum catalyst shape, gold-copper co-catalyst alloy nanoparticles and hydrous hydrazine reducing agent enables an increase of hydrocarbon generation from CO2 by a factor of ten. “Solar-energy-driven conversion of CO2 into hydrocarbon fuels can simultaneously generate chemical fuels to meet energy demand and mitigate rising CO2 levels,” explain Jinhua Ye and her colleagues at the International Center for Materials Nanoarchitectonics in their latest report. Now the research team have identified the conditions and catalysts that will maximise the yield of hydrocarbons from CO2, generating ten times previously reported production rates ("Photocatalytic Reduction of Carbon Dioxide by Hydrous Hydrazine over Au–Cu Alloy Nanoparticles Supported on SrTiO3/TiO2 Coaxial Nanotube Arrays"). Lund

A combination approach increases the generation of hyrdrocarbons from CO2 by a factor of ten. A) Scanning electron microscope image, the white arrows indicate the holes in the tubewall; B) Xray diffraction pattern of strontium titanate (STO)-titania (TiO2) coaxial nanotube arrays; C) transmission electron microscope image of Au3Cu@STO/TiO2 nanotube arrays; D) High-resolution transmission electron microscope image and fast Fourier transform pattern of Au3Cu nanoparticles. Carbon dioxide can be converted into a hydrocarbon by means of ‘reduction reactions’ - a type of reaction that involves reducing the oxygen content of a molecule, increasing the hydrogen content or increasing the electrons. In photocatalytic reduction of CO2 light activates the catalyst for the reaction. Ye and her team introduced four approaches that each contributed to an increased reaction rate. First, they combined two known semiconductor photocatalysts strontium titanate (STO) and titania (TiO2) – which led to the separation of the charges generated by light and hence a more effective photocatalyst. Second, the high surface area of the nanotubes was made greater by holes in the tube surfaces, which enhances catalysis by increasing the contact between the gases and catalysts. Third, the tubes were decorated with gold-copper (Au3Cu) nanoparticle co-catalysts to further enhance the catalysis, and fourth, they used hydrous hydrazine (N2H4•H2O) as the source of hydrogen. Although the high hydrogen content of hydrous hydrazine is widely recognised in the context of hydrogen storage there are no previous reports of its use for reduction reactions. The researchers demonstrated that the reducing properties of hydrous hydrazine were so great that oxidation of the co-catalytic nanoparticles – a problem when water or hydrogen are used - was avoided. The researchers conclude their report, “This opens a feasible route to enhance the photocatalytic efficiency, which also aids the development of photocatalysts and co-catalysts.”