Scientists have shown off what can be described as the world’s smallest electric car – made of a single, carefully designed molecule. The molecule has four branches that act as wheels, rotating when a tiny metal tip applied a small current to them. With 10 electric bursts, the car was made to move six billionths of a metre. The approach, published in Nature, joins recent single-molecule efforts, and seems to overcome the forces that often dominate at such tiny scales. The “batteries” of the electric car come by way of the tip of what is called a scanning tunnelling microscope – an extraordinarily fine point of metal that ends in just an atom or two. As the tip draws near the molecule, electrons jump into it.
The motor of the approach lies with the four “molecular rotors” that act as the car’s wheels; they undergo a change in shape when they absorb the electrons. The demonstration is a tour de force in what is called “bottom-up” nanotechnology. A wide array of machines has been demonstrated in recent years, incorporating parts etched to minuscule sizes from chunks of metals or semiconductors – a small version of traditional, “top-down” manufacturing.