Beautiful “flowers” self-assemble in a beaker

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"Spring is like a perhaps hand," wrote the poet E. E. Cummings: "carefully / moving a perhaps / fraction of flower here placing / an inch of air there… / without breaking anything."

With the hand of nature trained on a beaker of chemical fluid, the most delicate flower structures have been formed in a Harvard laboratory—and not at the scale of inches, but microns.

These minuscule sculptures, curved and delicate, don't resemble the cubic or jagged forms normally associated with crystals, though that's what they are. Rather, fields of carnations and marigolds seem to bloom from the surface of a submerged glass slide, assembling themselves a molecule at a time.

By simply manipulating chemical gradients in a beaker of fluid, Wim L. Noorduin, a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences (SEAS) and lead author of a paper appearing on the cover of the May 17 issue of Science, has found that he can control the growth behavior of these crystals to create precisely tailored structures.

Written By: Caroline Perry
continue to source article at seas.harvard.edu

8 COMMENTS

  1. Does this fall into the category of gaps in the fossil record, now filled ? Self assembly into complex things ? Oh nooooo. Wait. They will claim there was a designer who adjusted the chemicals.

  2. They remind me of fractal patterns I have seen in math books… I like to think about the details having details that have details etc… and you have all heard my wonder and awe of self assembly. It is jaw dropping. It is also an awesome piece of evidence against creation, but casually dismissed by most creationists I have spoken to (as are all facts that they encounter).

  3. There are also less artistic, but more useful forms of controlled crystal growth, in manufacturing computer chips.

    MG-Si is reacted with HCl to form trichlorosilane (TCS) in a fluidized-bed reactor (@300oC) according to the chemical reaction Si + 3HCl –> SiHCl3 + H2. TCS is an intermediate compound for polysilicon manufacturing. In the course of converting MG-Si to TCS, impurities such as Fe, Al and B are removed. This ultra-pure TCS is subsequently vaporized (distilling the TCS achieves an even higher level of purity), diluted with H2, and flowed into a deposition reactor where it is retransformed into elemental silicon. This polysilicon has typical contamination levels of less than .001 ppb.

    Now that a high level of purity has been attained (99.999999999% eleven nines), the atomic structure of the silicon must be dealt with. A process known as Crystal Growing transforms polycrystalline silicon into samples with a singular crystal orientation, known as ingots. The Polysilicon is mechanically broken into 1 to 3 inch chunks and undergoes stringent surface etching and cleaning in a cleanroom environment. These chunks are then packed into quartz crucibles for meltdown (at 1420oC) in a CZ furnace. A monocrystalline Silicon seed is installed into a seed shaft in the upper chamber of the furnace. Slowly, the seed is lowered so that it dips approximately 2mm into the Silicon melt. Next, the seed is slowly retracted from the surface allowing the melt to solidify at the boundary. As the seed pulls the Silicon from the melt, both the crucible and the seed are rotated in opposite directions to allow for an almost round crystal to form. CZ furnaces also must be very stable and isolated from vibrations. Once the proper crystal diameter is achieved, the seed lift is increased. This, along with the heat transfer from heater elements will control the diameter of the crystal.

    During the growth process, the crucible slowly dissolves Oxygen into the melt that is incorporated into the final crystal in typical concentrations of around 25ppma. Intentional additions of dopants control the resistivity distribution of the final crystal. In addition to pull speed and heat transfer at the solid-liquid interface, heat dissipation during crystal cooling strongly determines microscopic defect characteristics in the final crystal. For modern CZ pulling systems, those variables can be accurately predicted by numerical simulations which allow designing the geometrical and thermal configuration of the CZ puller to the desired outcome of the crystals. Once the growth process is complete, the crystal is cooled inside the furnace for up to 7 hours. This gradual cooling allows the crystal lattice to stabilize and makes handling easier before transport to the next operation. For some applications, it is important to have even lower concentrations of impurity atoms (eg. Oxygen) than what can be achieved by CZ crystal growth. In this case, Float Zone Crystal Growth is used. In this process the end of a long polysilicon rod is locally melted and brought in contact with a monocrystalline Silicon seed. The melted zone slowly migrates through the poly rod leaving behind a final uniform crystal. http://www.cleanroom.byu.edu/EW-formation.phtml

  4. As a kid I used to play with dropping various salts into sodium silicate to watch the strange crystal grow before my very eyes. I noticed in the fine print the image is artificially coloured. At first I was amazed how they could make sharp transitions in colour.

    • In reply to #5 by Roedy:

      As a kid I used to play with dropping various salts into sodium silicate to watch the strange crystal grow before my very eyes. I noticed in the fine print the image is artificially coloured. At first I was amazed how they could make sharp transitions in colour.

      A color SEM would be an amazing development in and of itself.

  5. These images are sooooo photoshopped! This is destroying the self-image of other self-building crystals, leading them to believe that they should all be colorful. :-)

    Incidentally, those chemical gardens are what first gave Mike Russell his ideas of how alkaline vents could have provided the first “cell walls” in which the chemistry of life could develop.

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