One of my favorite sites is the ILCS page. Every month, they post a different liquid crystal micrograph. It really is an amazing resource. And I'm not just saying that because they just selected one of our images (of a Smectic F phase) as their picture of the month for October 2015.

My Twitter feed has recently been atwitter with discussions of cheap cardboard microscopes, for example this one. This reminded me of an older discussion of building a microscope using only a laser pointer lens and a smartphone. One example can be found here, but there are many others. I decided to experiment with this. I found an old laser pointer and pulled out the lens.
  Constructing a microscope is a lot easier than the videos suggest. All you really have to do is place the phone on a flat surface and put the lens on top of the front lens of the phone camera. To the right is an image I took of a dragonfly's wing (thanks to my daughter, who supplied the subject.

The next step was to build a DIY polarizing microscope. This required two polarizers (I have a LOT of these lying around, being a polarized light geek), a light source (LED) and lens+phone assembly. The hardest bit was getting the sample (in this case adipic acid) at the correct focal length. All of this was done in the space of maybe 20 minutes.

I've posted earlier discussions about chiral liquid crystal phases, and in particular cholesteric phases, and how they can arise from "doping" a small amount of a chiral material into an achiral liquid crystal. Similar things happen when you add a chiral (nonracemic) dopant into other kinds of liquid crystal phases: smectic A phases can be made in chiral smectic A* phases, smectic C into C*, etc.
Some interesting things can happen at the transitions between chiral phases. For example, at the transition from a SmA* to short-pitch N* (cholesteric), the frustration caused by these two phases can give rise to a new kind of phase, called Twist Grain Boundary (TGB) phases. The image shown to the right has been tentatively assigned as a TGBA phase, but requires further characterization

As is so often the case, still images don't entirely get across the striking way in which these patterns develop. To the left is a short movie showing how the fibril texture grows in from the dark smectic A phase. At the end of the movie, the texture of the cholesteric phase appears.

When Reinitzer first observed the strange melting behavior of cholesteryl benzoate, he reached out to the microscopist Otto Lehmann for help. Lehmann had built a unique tool: a polarizing optical microscope with a heating stage. This opened up the world of liquid crystals, and continues to be one of the first methods employed in the characterization of liquid crystals. The video to the right is of cholesteryl benzoate. We are seeing what Lehmann would have seen more than a century ago.

One of the best pieces of advice I ever received regarding LC phase identification was to look at how the textures evolve over time and temperature. In that spirit, here is a short movie of the compound I discussed in the last post, which forms a smectic F phase.