What’s new with nanos ?
MINIATURISATION : TOWARD THE NANOWORLD
Smaller objects or devices are usually easier to transport, require less energy and produce less waste.
Miniaturisation has always been one of the priorities of science and engineering.
A classic example is the size and number of transistors in an integrated circuit (the computer’s brain)
Moore’s Law states that with progress in miniaturisation, the number of transistors in an integrated circuit of equal size doubles every 18 months.
Although this law has held since 1970, the sizes involved are closer to the limits related to the size of atoms (1/10 nm).
When things are miniaturised to nanometric sizes, it enables scientists to understand and exploit certain phenomena that are difficult to explain, in varied fields such as chemistry, physics and biology.
Lotus effect and Gecko effect
Nature abounds with many effects linked to nanometric size.
The Lotus effect
The surface of certain leaves and petals are covered with micropillars of water-repellent, hydrophobic wax. The droplets slide off, carrying dust with it and leading to a self-cleaning effect.
The Gecko effect
The toe pads of tokay geckos have microscopic hairs, lined with thousands of spatulae of with a width of approximately 200 nm.
These spatulae can make close contact with surfaces at nanometric distances.
At such distances, there are forces, or bonds between the molecules that are very weak but in very large quantities. They add up and enable the gecko to move on smooth vertical surfaces and even on ceilings!
The colour of nanoparticles (a quantum effect)
Although quantum physics is already the basis of such areas as electronics (transistors, computers, etc.) optics (lasers, etc.), quantum effects are sometimes "hidden" at the macroscopic scale. With the nanometric scale, they can be observed and exploited in their "pure" form.
Usually, the colour of an object remains the same whether it is big or small.
This is not the case on a nanoscale. Some nanoparticles, when lighted appropriately, for example, under ultraviolet light, display different colours depending on their size. It is a quantum effect that is observed only for nanometric sizes. Several nanometres of nanocrystals of semiconductors such as cadmium selenide (CdSe) are dissolved.
When they are exposed to ultraviolet light, they emit a fluorescent light with colours depending on the size of the crystals: blue at 2.3 nm, yellow at 4.5 nm and red at 5.5 nm.
This makes it possible to manufacture probes that can monitor chemical reactions or biological processes.
The tunnel effect (a quantum effect)
Although quantum physics has already been the basis for sectors such as electronics (transistors, computers, etc.), optics (lasers, etc.), quantum effects are sometimes "hidden" at the macroscopic level. With the nanometric scale, they can be observed and exploited in their "pure" form.
the marble thrown from point A cannot cross the barrier on the right
the "quantum" marble can cross the obstacle, from B to C, with a certain degree of probability, via a "tunnel" effect.
The tunnel effect enables the quantum electrons to cross the space, smaller than a nanometre, that separates a very fine tip of the surface of a sample. This would not be possible if they were "classic" electrons. That is the principle of the tunnel effect microscope.