Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.
Crystals are beautiful, fascinating materials that draw us in with their interesting properties. Refractive and reflective qualities aside, they have other properties too that we like such as their structure and composition. Some surprises await us when we take this closer look, and so we shall examine some fascinating applications of crystals you may never have thought of before.
It’s a common-enough idea that mentioning it seems ridiculous, but light is key to see anything and plays a role in certain processes. As it turns out, its absence can also change certain materials. Take for example zinc sulfide crystals, which under normal (illuminated) conditions will shatter if given sufficient torque. But removing light gives the crystal a mysterious flexibility (or plasticity), able to be compressed and manipulated without falling apart. This is interesting because these crystals are semiconductors, so with this property found it could lead to manufactured semiconductors with special shapes. Because of the lack of carbon, or inorganic, properties of the crystal, the band gaps between electron levels change under different light conditions. This causes the crystal structure to undergo pressure changes, allowing gaps to form where the crystal can compact without failure (Yiu “A Brittle”, Nagoya).
When scientists talk about memory we usually refer to electromagnetic storage devices that maintain a bit value. Some materials can maintain a memory based on how you manipulate it, and these are known as shape memory alloys. Typically, they have high-plasticity to ensure easy usage and need regularity, like the structure of a crystal. Work by Toshihiro Omori (Tohoku University) has developed a method to make such a crystal at a large enough scale to be effective. It essentially takes many smaller crystals and merges them to form long chains via abnormal grain growth. With repeated heating and cooling (and how fast it cools/heats) the little chains grow up to 2 feet in length (Yiu “A Crystal”).
Plants are green because they absorb light but reflect back green light, preferring the more efficient portions of the spectrum. But work by Heather Whitney (University of Bristol) and her team found that Begonia pavonina planets reflect blue light, iridescently. These plants are in low-light scenarios, so why would they reflect light that other plants would use? The story isn’t quite so simple, you see. When the cells of the plant were examined, the chloroplast equivalent known as iridoplasts were spotted. These perform the same function as a chloroplast but they are arranged in a lattice-like manner – a crystal! The structure of this allowed light that was left-over from the dark conditions to be converted to a more viable format. The blue wasn’t really restricting light, it was making sure that the resources present could be used (Batsakis).
The biological link to crystals isn’t just with those iridoplasts. Some theories about the formation of life on Earth posit that RNA acted as a precursor to DNA, but the mechanics of how it could form long chains without the benefits of things like proteins and enzymes that we have today are mysterious. Work by Tommaso Bellini (Department of Medial Biotechnology at Universita di Milano) and their team shows that liquid crystals – the state of matter that many electronic screens use today- may have helped. Under the right amounts of RNA as well as a proper length of 6-12 nucleotides, the groups can behave like a liquid crystal state (and their behavior grew more liquid crystal if magnesium ions or polyethylene glycol was present, but those weren’t present in Earth’s past) (Gohd).
When you look up at the night sky next time, know that you are looking upon not only stars but crystals also. Theory predicted that as stars age as a white dwarf, the liquid inside of it eventually condenses into a solid metal that is crystalline in structure. Evidence for this came when the Gaia telescope looked at 15,000 white dwarfs and looked at their spectrums. Based on their peaks and elements, astronomers were able to infer that the crystalline action was indeed occurring in the interiors of the stars (Mackay).
I think it’s safe to say that crystals are freaking awesome.
Batsakis, Anthea. “Shimmering blue plant manipulates light with crystal quirks.” Cosmosmagazine.com. Cosmos. Web. 07 Feb. 2019.
Gohd, Chelsea. “Liquid crystals of RNA could explain how life started on Earth.” Astronomy.com. Kalmbach Publishing Co., 04 Oct. 2018. Web. 08 Feb. 2019.
Mackay, Alison. “Stars like our Sun turn into crystals late in life.” Astronomy.com. Kalmbach Publishing Co., 09 Jan. 2019. Web. 08 Feb. 2019.
Nagoya University. “Keep the light off: A material with improved mechanical performance in the dark.” Phys.org. Science X Network, 17 May 2018. Web. 07 Feb. 2019.
Yiu, Yuen. “A Brittle Crystal Becomes Flexible in the Dark.” Insidescience.com. American Institute of Physics, 17 May 2018. Web. 07 Feb. 2019.
---. “A Crystal That Can Remember Its Past.” Insidescience.com. American Institute of Physics, 25 Sept. 2017. Web. 07 Feb. 2019.
© 2020 Leonard Kelley