LEARN #2 – Week 116 of my PhD

Welcome back! We are at the second issue of LEARN, which is a big deal for me! I tend to start lots of things, but never stick on them..

But let’s start with the fun!



Vaterite is a polymorph of calcium carbonate (CaCO3). It is a interesting material for optical trapping, because it is birefringent: for everyone working in the field of optical manipulation, this information immediately translate as “Let make it rotate!”. In fact, using a circular polarised laser on a microsphere of vaterite will result in the vaterite particle spinning because of the angular moment transfer from the beam to the material. Interestingly enough, microsized vaterite beads can also be trapped in vacuum, removing the contribution of the viscous forces of the surrounding medium on the rotation. The reason I know about it, it is becausa Monday I went to visit a lab nearby: Kishan Dholakia’s group at St. Andrew University. I wish I had done it before! It was bombarded with information, but my background of material physicist made me choose to talk about vaterite. Plus, everyone likes to spin! Check some of Dholakia’s group’s papers to know more!

BONUS: Vaterite is one of the few calcium carbonate that can be precipitated in conditions miming Mars environment. And it does it beautifully, making lovely rosettes (pictured)!

l2_tueMore on optical manipulation. At the Journal Club during the Group Meeting, one of my peer presented a paper about levitated polystyrene ellipsoids. When the ellipsoids are pushed against the top coverslip of the chamber, instead of showing a static behavior as per the microspheres, they start to oscillate back and forth in a movement that the researcher called, I am pretty sure just for my own amusement, ‘Ellipsoid’s Waltz’ (pictured).

l2_wedOff the coast of Taiwan, Iriomote-jima stands the oceanic currents and over the centuries collects what left of the offspring of the North Star and the Southern Cross, that born in Okinawa sea was then swallowed by the evil serpent that left just their tiny star-shaped shells behind. Or so the legend says. In reality these beautiful star-shaped shells (pictured), that form the sand in this remote island of the Okinawa prefecture, are the exoskeletons of single-celled organism called Baclogypsina sphaerulata, a type of Foraminifera.  These protists form their shell from organic compounds, sand grains and other particles cemented together, or crystalline calcite, according to the species. The largest Foraminifera ever found, of the specie called Syringammina fragilissima, measured 20 cm: quite impressive for a single cell! It is found in Scotland, but this is a not a good reason for me to try to look for one, since reaching the granite islet of Rockall might be far more complex than planning a trip to Japan!

l2_thuThursday = New Nature Issue, and this is how I get connected with the world of science that does not encompass my field. I haven’t read everything in the issue yet, but something to pick from it is the largest photon teleportation ever experimented: over 30km of fiber, basically across a city. The cake is real (almost)!


Fri-nally! I did lots on Friday, but many of my tasks could have been done by a well-trained monkey: I was repeating the same measurement over and over again without many Eureka moments. The only thing I learnt came from a link a friend of mine sent me over the week, to help me fix a problem with my microscope set-up. In fact, for the way my system is configurated I need to illuminate and image the chicken embryo I work with sometimes in reflection. But the contrast is not great, and I ended up having the illumination set-up at 45 degree. This results in poor images with lots of artifacts. He recommended using some circle of LED illumination around the sample instead, and recommended some site to enquire for prices or some cheap(ish) option for a DIY project. Of course I am going for the DIY and I hope to post something soon about it.

Worst case it does not work, and I end up with plenty of LED that I can use for instance to make crazy-evil-scientist goggles (pictured): always necessary if you do my job!

Well, have a nice week folks, and keep LEARNing Every day A Remarkable Notion! 🙂

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