Polarised Light Microscopy

Fractals in Amino Acids

L-arginine is one of the essential amino acids in biology which plays a role in balancing the electronic charge of a protein, ultimately to maintain its conformation. Here we can see frozen droplets of L-arginine. Transparent to the unaided eye, but when placed between crossed-polarisers, suddenly we can see the unseen, giving us a new perspective. Because the molten droplets were supercooled to a temperature below its freezing point, the convection currents had not time to dissipate and so appear frozen in space and time taking up a branching fractal-like pattern. In fact, it is not the convection currents which are frozen, but the material transported on these currents which have become solidified in space and time. The process of changing from a viscous state to the glass state is called vitrification.

Viscous Worlds

Found in the cytoplasm of all cells, L-arginine is an essential amino acid which is involved in the synthesis of proteins through RNA translation. When the temperature of this substance is increased through the glass-transition temperature, it gradually changes state from a solid to a viscous state called a non-Newtonian fluid. Such a fluid exhibits both liquid and solid like properties and is said to be viscous. Here, some of these viscous droplets have pooled around air bubbles.

Organic Tessellation

Botanical Tessellation

Mixed in specific proportions, lactic acid and acetylsalicylic acid or aspirin as it is better known produces remarkable tessellations. There are two stages of crystallisation processes in this mixture with this being the second phase.

Niacinamide Flower (Vitamin-B3)

Circular shaped crystals called spherulites grow radially from a central nucleation point. The nucleation point could be a dust particle or undissolved crystal grains in the liquid phase. During the crystallisation process, molecules precipitate from the liquid solution and undergo adsorption onto the growing crystal faces. The Maltese cross-like pattern visible in each spherulite corresponds to those molecules which are orientated in such a way as to lie perpendicular to the optical axis of the analyser.

Psychoactive Drugs

Commonly used in our daily lives, caffeine improves our mental awareness by stimulating our central nervous system. Caffeine crystals exhibit anisotropic structural properties in their crystalline form, giving rise to acicular or needle-shaped morphologies. Anisotropic in terms of the crystalline lattice means that the arrangement of atoms or molecules in one set of planes is different in another while in contrast, atomic planes are symmetrical in all directions in an isotropic lattice. This means that one face of the crystal is susceptible to adsorbing and making stronger molecular bonds with other molecules more so than its other crystalline faces.

Growth of Niacinamide

Timelapse movie of the crystallisation of niacinamide (Vitamin-B3). The crystal grains called spherulites grow radially from seed crystals located at random points in the frame.

Sugar Solution

Sugar Solution

Ammonium Nitrate

Branching Creatine

A close-up of Creatine magnified approximately 150 times. Initially, forming a heterogenous mixture, minute crystals of creatine were suspended in a solvent of water. The crystals, jittering about in the molecular storm of Brownian motion, undergo random walks, colliding and adhering to other crystals. Over time, these clusters increase in size, eventually forming the branched fractal structure seen here, called a Brownian Tree. This self-assembly process is called diffusion-limited-aggregation (DLA). The colours in the image are a result of thin film interference. Residual water fills the spaces between the branches. Surface tension causes the top surface of the water to form a meniscus along the branches. As such, close to the branches there is a sudden change in thickness of the fluid film which leads to a change in the wavelength (colour). Regions of the same colour correspond to equal film thickness.

Dopamine ‘Skittle Rain’

A small quantity of powder dopamine was placed on a glass slide and heated to a temperature exceeding its melting point. In doing so, it sizzled and splattered across the substrate, forming a random distribution of pools and microdroplets on the glass surface. In time, as the temperature decreased, these droplets slowly changed phase from liquid to the crystalline state were the molecules orientate themselves in such a way that the overall crystal exhibits an optical property called birefringence. Depending on both the thickness and orientation of the crystal grains, the frozen droplets appear to take on different interference colours.

Fractured Flake of Paracetamol (Acetaminophen)

A perfect circle is a set of points on a plane which are all equidistant from a fixed point.

Fluid dynamics

Invisible made Visible

Fluid dynamics is the branch of physics describing the flow of liquids. The movement of liquid can be categorised as laminar or turbulent and the magnitude of that flow can be quantified by the Reynolds number. In this case, the fluid flowing around, and in the wake of the bubbles is smooth and laminar. This of course makes sense because the fluid here is a viscous ‘gloup’ of molten sucrose or table sugar and the bubbles move relatively slowly through it. Otherwise invisible, the flow is made visible here through a technique called differential interference contrast.

Brilliant Radiance in Vitamin-C (Ascorbic acid)

Four large crystals surrounded by an extremely thin film of Vitamin-C. The thin film, illuminated from beneath with plane-polarised light, results in strikingly colourful optical interference patterns. These patterns arise due to the complex interplay between the illuminating light field and the atomic planes of the doubly refracting crystal lattice. Bands of the same colour correspond to equal or integer multiples (1, 2, 3, …, n) of the wavelength differences in pathlength through the crystal. Dislocations in the crystal film can be seen as straight lines where the coloured bands appear to converge.

Radiant Vitamin-C (Ascorbic acid)

Two large bulk crystals surrounded by an extremely thin film of Vitamin-C. The thin film, illuminated from beneath with plane-polarised light, results in strikingly colourful interference patterns. These dazzling patterns arise due to the complex interplay between light and the doubly refracting or birefringent crystal film. Bands of the same colour correspond to equal or integer multiples (1, 2, 3, …, n) of the wavelength differences in pathlength through the crystal. Dislocations in the crystal film can be seen as straight lines where the coloured bands appear to converge.

Ascorbic Acid

Ascorbic Acid

Dopamine

Voronoi Lattice - Dopamine Kaleidoscope

Powdered dopamine was smeared across a glass slide, melted and cooled to give rise to the formation of a vast number of individual crystal grains as it undergoes a change of phase from a liquid to a solid crystalline state. Because of the physical structure of this substance, dazzling kaleidoscopic colours can be seen when viewed through crossed polarisers. Such materials are said to be optically active as they twist the plane of polarisation of light.

Dopamine

Dopamine

Amino Acids

Psychedelic Amino Acids

This trippy psychedelic image was produced by mixing the essential amino acids, beta-alanine and L-glutamine in a specific ratio and dissolving the mixture in a solvent. The solvent was evaporated allowing the molecules to come out of solution and to adsorb onto the faces of the radially growing crystal from its nucleation point. Through experimentation of controlled cooling rates and other environmental factors, different types of crystal structures can be fashioned. However, it is never possible to reproduce such a complex crystal structure exactly since all crystals have defects inherent in their lattice structure. In essence it is never possible to reproduce any of these images.

Dopamine

Dopamine

Dopamine

Dopamine

Dopamine

Dopamine

Air Cavities in a Viscous Sugary Solution

In a race to minimise energy and reach an energetically favoured state of equilibrium, a tug-of-war ensues between many thousands of trapped air pockets and the compressing effects of the surrounding viscous liquid. A bubble is a balancing act of forces that occur between it's internal air pressure pushing outward on its membrane and the compressive forces of the surrounding liquid trying to crush it inwards. As a result, the molecular field density and thus the optical path length surrounding the air pockets will be significantly distorted. This effect can be seen by the vivid coloured bands immediately surrounding the bubble aggregations.

Bubble Cluster

A Shower of Acetanilide

Acetanilide Rainbow

Acetanilide

Acetanilide

Geological Formation

A specific ratio of two amino acids, when mixed and dissolved in a solvent and allowed to undergo evaporation, results in this stunning crystalline formation. The amino acids are beta-alanine and L-glutamine. The L donates that the molecule has a left-handed structure, as opposed to a right-handed structure. When a plane-polarised light beam interacts with such a left-handed molecule, the electric field vector of the light wave is rotated through some angle (theta) in an anti-clockwise direction. In this case the molecule is said to be laevorotatory. All amino acids that link together through peptide bonding to form proteins are left-handed amino acids.

Dopamine