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Category: materials – Page 289
Very cool; another example where nature inspires others. Einstein was inspired often by nature and its environment.
Titanium is used medically in applications such as artificial joints and dental implants. While it is strong and is not harmful to tissues, the metal lacks some of the beneficial biological properties of natural tissues such as bones and natural teeth. Now, based on insights from mussels—which are able to attach themselves very tightly to even metallic surfaces due to special proteins found in their byssal threads—scientists from RIKEN have successfully attached a biologically active molecule to a titanium surface, paving the way for implants that can be more biologically beneficial.
The work began from earlier discoveries that mussels can attach to smooth surfaces so effectively thanks to a protein, L-DOPA, which is known to be able to bind very strongly to smooth surfaces such as rocks, ceramics, or metals. Interestingly, the same protein functions in humans as a precursor to dopamine, and is used as a treatment for Parkinson’s disease.
Using a combination of recombinant DNA technology and treatment with tyrosinase, they were able to create a hybrid protein that contained active parts of both the growth factor and L-DOPA. Tests showed that the proteins were able to fold normally, and further experiments in cell cultures demonstrated that the IGF-1 was still functioning normally. Thanks to the incorporation of the L-DOPA, the team was able to confirm that the proteins bound strongly to the titanium surface, and remained attached even when the metal was washed with phosphate-buffered saline, a water-based solution. Zhang says, “This is similar to the powerful properties of mussel adhesive, which can remain fixed to metallic materials even underwater.”
Nice.
“Our study suggests for the first time that the doping-induced modulation of the charge carrier density in graphene influences its wettability and adhesion,” explained SungWoo Nam, an assistant professor in the Department of Mechanical Science and Engineering at Illinois. “This work investigates this new doping-induced tunable wetting phenomena which is unique to graphene and potentially other 2D materials in complementary theoretical and experimental investigations.”
Graphene, being optically transparent and possessing superior electrical and mechanical properties, can revolutionize the fields of surface coatings and electrowetting displays, according to the researchers. A material’s wettability (i.e. interaction with water) is typically constant in the absence of external influence and are classified as either water-loving (hydrophilic) or water-repelling (hydrophobic; water beads up on the surface). Depending on the specific application, a choice between either hydrophobic or hydrophilic material is required. For electrowetting displays, for example, the hydrophilic characteristics of display material is enhanced with the help of a constant externally impressed electric current.
“What makes graphene special is that, unlike conventional bulk materials, it displays tunable surface wetting characteristics due to a change in its electron density, or by doping,” said Ali Ashraf, a graduate student researcher and first author of the paper, “Doping-Induced Tunable Wettability and Adhesion of Graphene,” appearing in Nano Letters. “Our collaborative research teams have discovered that while graphene behaves typically as a hydrophobic material (due to presence of strongly held air-borne contamination on its surface), its hydrophobicity can be readily changed by changing electron density.
Way cool.
Ideally, injectable or implantable medical devices should not only be small and electrically functional, they should be soft, like the body tissues with which they interact. Scientists from two UChicago labs set out to see if they could design a material with all three of those properties.
The material they came up with, published online June 27, 2016, in Nature Materials, forms the basis of an ingenious light-activated injectable device that could eventually be used to stimulate nerve cells and manipulate the behavior of muscles and organs.
“Most traditional materials for implants are very rigid and bulky, especially if you want to do electrical stimulation,” said Bozhi Tian, an assistant professor in chemistry whose lab collaborated with that of neuroscientist Francisco Bezanilla on the research.
Definitely makes sense when you consider how things work in nature.
Generally, water repellent objects and those that attract or absorb water have very different microscopic-level attributes that endow them with their behavior. For example, the myriad tiny hairs on a gecko’s body help it to efficiently repel water, whilst specially treated cotton designed for harvesting water from the air contains millions of tiny pores that draw in liquid. Now researchers have discovered a way to use a single type of material to perform both functions, switching between liquid attraction and liquid repulsion, simply through the application of an electric voltage.
Developed by a team of scientists from TU Wien, the University of Zurich, and KU Levin, the new material alters its water-handling behavior by changing its surface structure at the nanoscale to effect a change at the macroscale. Specifically, the behavior of liquid on the new material is as a result of altering the “stiction” (static friction) of the molecular surface. One with a high-level of stiction keeps moisture clinging to it, whilst one with a low-level allows the liquid to run right off.
To change the amount of stiction, a nanoscale mesh made of a single layer of boron nitride (or “white graphene”, as it is sometimes known) was grown on a bed of rhodium, to create a honeycomb structure with comb depths of around 0.1 nanometers and comb to comb distance of 3.2 nm. When a voltage is applied to the structure, the mesh flattens out, changing the contact angle between the water droplets and the molecules so greatly that surface tension can no longer be maintained, and the droplets lose their grip on the surface.
Great writeup and goes well with the other posting on DiAmanti’s new perfected synthetic diamonds.
Scientists in Japan have successfully recorded the atomic bonds between diamond and cubic boron nitride: the hardest known materials on earth. This feat could ultimately lead to the design of new types of semiconductors.
Diamond is the hardest material in existence but is useless for cutting steel because it reacts with iron, from which steel is made, at high temperatures. Cubic boron nitride, a synthetic material, is the second hardest substance after diamond but is chemically stable against iron at high temperatures. If desirable composites of diamond and cubic boron nitride crystals could be obtained, a unique machining tool could be developed for work on hard rock and substances that contain iron. Also, a better understanding of the bonds formed between these two unique semiconducting materials could lead to the development of new types of semiconductors. The nature of these bonds was previously unknown.
Reporting their findings in Nature Communications, a team of researchers at Tohoku University, the National Institute for Materials Science and the Japan Fine Ceramics Center imaged bonded diamond and boron nitride, both crystalline materials, using a super-high-resolution scanning electron microscope. The team then subjected those observations to extensive theoretical calculations.
