Polymer Carpets

Hannah Bruce Macdonald

It seems as though every new development nowadays is on the nano-scale, and this is no exception. Professors from the University of Munich and the University of Dresden have improved a method for the synthesis of polymer carpets.

A Polymer Carpet

Polymer carpets are made by grafting styrene polymers onto copper supported graphene and these scientists have discovered that the carpet density and thickness depends on the hydrogenation of the graphene. Graphene is an incredible material, due to its versatility, but what makes it so useful as a support for making polymer carpets is how stable it is to mechanical and chemical influences. The team working on these carpets say that the ‘Polymer carpets exhibit remarkable and unprecedented properties combining extreme thinness, mechanical and chemical stability, robustness, flexibility, and (chemical) sensitivity’. The chemical sensitivity mentioned by the team may sound like a flaw, but this actually means that the nature of the carpet (effectively its thickness, fluffiness or tangled-ness) can be fine-tuned with changes in conditions like the solvent quality, wetting and pH.

Natural (left) and artificial (right) nacre

Polymer carpets are one of those materials that seem to be good at everything. They are similar to biological membranes, such as the outside layer of cells, but have the significant advantage of stability and the ability to withstand considerable pressure. This feature means they have been applied to use in water purification and desalination. Any developments in these fields are of huge importance globally and more research and discoveries in this field could make these polymer carpets a viable solution to the cleanliness of drinking water.

Another unsuspected use of these is in the synthesis of artificial nacre. If, like me, you don’t know what nacre is, it is mother of pearl, the shiny inside coating of some seashells and the outer surface of pearls. Pearls have had many uses over the years, but these tend to be mostly decorative, in jewellery or furniture, but are beginning to be applied in more areas. The pearl is originally made as a surface to protect the molluscs’ soft material from damage through bombardment and protection from parasites. Nacre is now being used as a novel material in medical surgery, as it has been shown to stimulate the growth of cartilage when injected into bones. The ability to make a Nacre alternative in the labs could prove to be advantageous, over having to source it from the sea.

Any improvements in the understanding of the mechanism or the synthesis of polymer carpets is useful, and allows a large step to be taken towards applications such as these, however the greatest use of these diverse materials could yet to be discovered.

Batteries Breakthrough

Hannah Bruce Macdonald

Having been around for 200 years, you wouldn’t think that there would be much room for improvement in the field of Batteries. However, scientists at Massachusetts Institute of Technology (MIT) have managed to outdo themselves (and Duracell) by designing a battery large enough for grid-scale storage. Currently, the National Grid is playing the balancing act between the output of their generators and the consumer demand; which is particularly difficult when maintaining an alternating current (AC) of 50 Hz. This can’t be taken lightly with the responsibility of more than a slight fluctuation in this AC can cause electronic devices to fail in power surges.

The storage of energy would ease the stresses of this supply management, but the scales of energy concerned are huge and it is not as simple as building a comedy-sized battery. A normal dry-cell battery scaled up would require the combination of thousands of individual, can-sized, cells to be linked together; a complex and expensive solution. 

Liquid metal batteries may be the answer to this. In very basic terms the battery can be explained as a sandwich of three metals, a molten-salt electrolyte with a sunk, dense positive electrode and a light, floating negative electrode. The difference between the floating and sunk metals is what causes the voltage. This design is much reduced in complexity, making it a much more feasible option. With the figure of $15 million in investments from Bill Gates, Total and others, this new battery has been described as a cheap potential. This clever battery would be capable of charging from the Grid during the night while acting as a secondary generator at peak times during the day. Terrifyingly, the demand for electricity is predicted to exceed its supply in Manhattan in less than three years. This electricity crunch could be solved by these batteries storing excess energy at low times and then releasing it again when required. These batteries also lend a hand to renewable energy sources, such as wind and solar power, which cannot be relied on for consistent 24 hour supply.

The structure of a liquid metal battery

These batteries are still in relatively early development and the company Ambri are playing their cards close to their chest while they fine-tune and scale up their batteries to protect their design. The development in this area is still open with no front runner between liquid batteries and other options such as redox flow, lithium-ion and sodium-ion batteries. There may not be enough letters in the alphabet to label these batteries, but all I know is that I wouldn’t try licking it.

Graphene: The Future of Computers?

Hannah Bruce Macdonald

Graphene is a one atom thick sheet of pure carbon, with a hexagonal pattern much like graphite. Its structure causes graphene to allow very rapid movement of electrons across the sheet, and it is this property that has caused graphene to be flagged for use in ultra-fast computers. However, the nature of transistors require them to be semi-conductors like Silicon, allowing the circuit to be turned on and off by a band gap in the material. A band gap is a difference in energy between the energy of the electrons and the energy required to conduct, with the band gap being bridged only when the correct amount of external energy is applied. Graphene does not have a band gap and therefore does not semi-conduct. 

Computer chip with over 1 billion transistors

A band gap has been introduced into Graphene before, allowing the application of Graphene to transistors. This has been done using techniques such as adding an insulating layer to the Graphene, reducing its conductivity, or through carving the Graphene into ribbons, where the altered structure allows the current to be turned off more easily. Both these previous techniques have been successful, but are limited in their scope as they only work in transistors above a certain size, as the edges of the ribbons become roughly cut at small sizes, allowing the band gap to disappear.

New research carried out at the Georgia Institute of Technology has found that graphene sheets designed with a rippling surface could be used for transistors. The troughs in the rippled surface mimic the ribbon, but as it is made of one continuous sheet, the issue of the edges of the ribbons has been bypassed. The parallel trenches are 18nm deep and have a band gap of 0.5 electron volts. This development has opened up the opportunity for graphene to replace silicon in transistors in the future, but there is still plenty of research to be done into the band gap, to produce the ideal sized graphene ripple. This potential shift from silicon to graphene transistors could push Moore’s Law to its limits, as the law states that processor speeds and the number of transistors on a computer chip would double every two years.

Will rippling the surface of graphene make them the ultimate transistor?