H2O Crystals – Hokkaido

Walking in Sapporo I came across this icy wall are if ice blocks of frozen water crystals. It is a subject of interest, because ice connects us in so many ways.

Let’s start with the basics. The molecules in a solid have little energy and forces between the molecules hold them in a rigid, solid form. As the temperature increases, the molecules gain more energy and therefore vibrate more, breaking the weaker forces holding them together and becoming a liquid. If you give the molecules even more energy, they can completely break the forces holding them in a liquid and become a gas.

So for a solid to form from a liquid, the molecules must be cooled below their freezing point, allowing bonds between molecules to form. The formation of ice from water starts with small crystals being formed in the liquid. The water molecules in the liquid surrounding the crystals must then bond to the these crystals until everything has become a solid.

The shapes of ice crystals are also interesting. Water is made up of two hydrogen atoms and an oxygen. Because the oxygen is a bit greedy, it pulls the electrons involved in the bonds with the hydrogens towards itself. This results in the oxygen having a slight negative charge and the hydrogens a slight positive charge. During the formation of a solid, this charge distribution results in interesting motifs.

So why is ice important? First of all, crystals are useful in all sorts of applications, and we would like to know how to grow them better. Computers are carved out of silicon wafers, which in turn are cut from large silicon crystals. Many other semiconductor crystals are used for other electronics applications.

Lasers are also made from crystals, and a variety of optical crystals are used extensively in telecommunications. Artificial diamond crystals are used in machining and grinding. The list of industrial crystals is actually quite long.

By studying the physics of snowflakes, we learn about how molecules condense to form crystals. This basic knowledge applies to other materials as well. As we learn more about the physics and chemistry of how crystals grow, maybe someday we can use that knowledge to help fabricate new and better types of crystalline materials. This is the way that basic science becomes useful — figure out how things work the best you can, and later on use that knowledge in unforeseen applications.

Nature uses a completely different approach to manufacturing. In nature, things simply assemble themselves. Cells grow and divide, forming complex organisms. Even extremely sophisticated computers (such as your brain) arise from self-assembly. The snowflake is an very simple example of self-assembly. There is no blueprint or genetic code that guides the growth of a snowflake, yet marvelously complex structures appear, quite literally out of thin air. As we understand better how snowflakes form, we learn about self-assembly.

As the electronics industry pushes toward ever smaller devices, it is likely that self-assembly will play an increasingly important role in manufacturing. Learning about self-assembly from the ground up will probably by useful in this context also. Again, in the study of basic science we try to solve the easy problems first (like snowflakes), and later use that knowledge to develop engineering applications we cannot yet foresee.