Store Denser, Separate Smaller, and Detect Lighter

Image source: "Scientific American" Sept. 2004
Related article: "Atomic Spin-offs for the 21st Century", September 2004; by W. Wayt Gibbs

There is a collection of articles about the most famous scientist in last century, Albert Einstein, in "Scientific American" this month. (Well, for English version, it's last month.) In those articles, there is one talk about 3 important inventions which based on Einstein's work.

The first is a electronic circuit which can control the spin of electrons by the effect of Relativity. The basic idea of this device is that when high speed electrons pass though the electric field applied form the gate of the circuit, for the electrons, part of the electric field will become magnetic field and that will rotate the direction of spin of the electrons which pass though gate. As the applied electric field is gone, the rotation of spin will stop. Therefore, if we properly control the applied time of electric field, we can "write bit" the direction of spin and by "read bit" by detecting the spin of electrons. And it will become a high density storage method, because more precisely we can detect the direction of spin, more "digital state" of spin we can separate, and that means more densely we can can store. According to the author, scientists can do it quite well by modern technology.

The second is a sorting method which can separate nano-meter-scale bio-molecular by the effect of Browian motion. Small particles in fluid will be strike by many surrounding fluid molecule, then randomly "jump" in the fluid, and this phenomenon is called as Browian motion. The devise, "Browian ratchets", is a micro-channel which many nano-boards with same orientation are within and the samples and fluid flow pass in different direction. As the samples in different sizes pass the micro-channel, the smaller one will jump more by the effect of Browian motion, and there will be more chances, they will guided by the nano-boards. On the contrary, the larger one will not jump as largely as smaller one and pass with the flow. Then, after the trip the micro-channel, the larger and smaller samples will go on different road.

The last is a gravity detector based on Bose-Einstein-condense, which I have heard about that many years age. It's a technology to observe the population distribution of atoms in very low temperature that makes them show the property of Boson.

Above all, I think all those interesting inventions is based on the phenomena of pure physics, and that's why those devices are beautiful. As a philosophizer ever said, "fundamentals are the building blocks of fun!"