Windscreens that no longer steam up, or paint that no longer gets dirty or can be scratched: all this could be everyday reality for car drivers in just a few years time. As part of their research work, engineers at the BMW Group are examining the use of nanotechnology in future cars. The range of possibilities is large. Currently the company is working on an agent that will counter dirt and paint damage, and small nanoparticles are of great help in this.
Purchasing a new car in 2020 - the scenario: the showroom dealer, in addition to exhibiting BMW's latest shiny new models, also sets up a stand with small, colourful seed packets. The packets, however, do not have pictures of exotic plants printed on them but instead car models. The customer chooses a car, pays for it, and is then handed over his dream car in a seed packet. He scatters the seed in his garden and waits, and at some point, just like a flower, his dream car sprouts up from the earth. Atom by atom, molecule by molecule.
What today seems like science fiction could tomorrow be reality. This is because there is no reason why objects cannot be created on an atom by atom basis, the proof for this being provided as far back as 1959 by American physicist and Nobel prize winner, Richard Feynman. In 1986 US researcher Eric Drexler too prophesied that: "In the future programmable molecular-sized robots will be able to grab hold of individual atoms and place them at the exact location where we want them to be. We will be able to replicate each new object atom by atom, be it a strawberry or a car." Just one year later the first step in this direction was taken when the decisive tool for conquering the atomic world was discovered. Since then scientists have been able to precisely design and mix the building blocks of the universe. Also possible now is the construction of artificial molecules which can be used as minute machines - almost exactly as Drexler prophesied.
Drexler and Feynman are considered the intellectual fathers of nanotechnology. To some extent it is a dwarf science, as "nanos" in Greek means "dwarf", and a nanometre in physics corresponds to one billionth of a metre or one millionth of a millimetre.
The number of uses that can be made of nanotechnology in the car industry is enormous. Take, for example, scratch-free windscreens: If one mixes silane, large molecules made of silicon, metal and alcohol groups, with water, these convert into silanols, which in turn develop into blobs several nanometres in size. Chemically elongated molecules can be attached to these, the ends of which contain the chemical element, fluoride, familiar because of its use in toothpaste. If one removes the water from this mix, referred to as "sol", the blobs form an unbroken network.
"In this way a viscous gel is created", explains BMW's nano-expert, Dr. Michael Nikolaides. If this gel is then applied to vehicle surfaces, the molecules with their fluoride heads behave on the open surfaces in accordance with the laws of thermodynamics. "It is this layer of fluoride ends that makes it hydrophobic - like in the case of a Teflon frying pan", explains the nano-expert. The characteristics of these coatings offer considerable advantages: The coating is transparent and can be applied as clear lacquer over the paint on the vehicle body. Furthermore it can be water-resistant, so that dirty water does not dry into a layer of dirt on it. This lotus flower effect, also called "easy-clean", allows water to trickle down more easily and makes it almost impossible for dirt to latch on to paint. The BMW Group is carrying out research into this effect, which is called "hydrophobing". Water, when it comes into contact with the fine nanostructures on the leaf surfaces of the lotus plant, trickles down very easily and takes all the dirt with it. This is also the idea behind special nano paints; graffiti created using such paints can be wiped off as easily as chalk from a blackboard. "One disadvantage of such artificial coatings up until now has been their lack of permanence, as artificial coatings, in contrast to plants, do not grow again", explains Nikolaides. Using nanotechnology the paint on a vehicle could even be designed as a solar cell, although this has yet to be realised. The electricity generated from such a cell while the vehicle was stationary could be used to recharge the battery or to cool the inside using a heat pump. This is still a long way off, however. Help with air-conditioning is provided in the form of windscreens that incorporate nano-scale components, which, depending on the current applied, increase or decrease the rate of light and thermal radiation. Even today vehicle light is produced using nanotechnology, with the LEDs of high-quality braking lights equipped with nanometre-scale layer systems that convert electricity into light more efficiently. Another plus point: LEDs convert electricity directly into light visible to the human eye, whereas braking lights and light bulbs take a little longer to do this. This difference can represent several metres braking distance. By now the intensity of LEDs is so high that grouped together they can create the dipped beam of front headlights.
Darkening rear-view mirror
Additional uses for gigantic nanoparticles can be found in the area of screen technology. The BMW Group is using this technology in rear-view mirrors, where nanoparticles can cause an electrochemical effect to take place i.e. the darkening of a screen in response to light incidence. Electrochrome glass is made up of laminate composed of several layers, and if one applies a current of just a few volts between the two electrode layers, light-alloy lithium ions will pass through a plastic layer and link up with a metal oxide to form a complex that can absorb light. This is turn results in the screen darkening. If one reverses the polarity of the current, the metal oxide complex dissolves itself again. This process takes several minutes, however. "In just a short period of time we can darken a screen by up to 80 percent", comments a spokesperson at the BMW Group.
Sensors for the analysis of driving conditions
Driving on cold, wet winter days has one disadvantage: ice on the road only becomes noticeable when you start skidding. Glancing at the temperature indicator is also of little use. It would be much better if a car were able to reliably inform the driver each time ice began to form on the road, and this is where sensors that are able to analyse driving conditions come in handy. Small laser sensors designed for this purpose have already been introduced onto the market, but the car industry is in the process of developing even smaller ones. So-called quantum points, i.e. large blobs up to ten nanometres in size and consisting of semi-conductors, can, depending on the energy feed, conduct electricity. If one places millions of them - like jam into a doughnut - into another semi-conductor, they can be tuned to emit ultra pure laser light. This technology could then be used to examine for ice on the road. The principle behind it is the following: The laser light excites water molecules in the ice, which as a result emit radiation, and this in turn is picked up by a detector in the vehicle.
Nano-dwarves as environmental angels
Another possible application for nanotechnology is in the area of fuel cell technology and with respect to efficient pollutant filters. The target in this case is to drastically reduce fuel consumption, pollutant emissions and vehicle wear. One possible first step could be the coating of the inlet valves of catalytic converters. In the case of direct injection petrol engines, burnt fuel re-enters the combustion chamber through these inlet valves, and as a rule, unwanted hydrocarbons then deposit themselves inside the chamber. A catalytic valve coating breaks them up and prevents depositing from taking place. BMW has already introduced onto the market a catalytically coated filter system for diesel cars that is able to function without any need for additional fuel. In the distant future filters could be developed that, with the help of nanopores or forests of carbon nano-tubes, are able to capture pollutants even more efficiently. Adding nano-additives to petrol or cylinder walls could even result in catalytic converters being made redundant altogether. A definite timeframe for the introduction of these technological innovations has yet to be drawn up, however.
The engineers in BMW's materials concepts and simulations department are looking into all the various possible applications of nanotechnology, and in each area one engineer is responsible for keeping an eye on the technology, so that synergies can be used and possible applications discussed. According to Nikolaides there is no doubt whatsoever that the little helpers will facilitate driving in the future. Drivers, however, should dispel themselves of the notion that one day the existence of little nano-robots will result in problem-free driving. "That", says BMW's nanospecialist, "is something firmly in the realm of science fiction."