Hollow core photonic crystal fiber as a viscosity sensor

Determining viscosity of nano-liter liquids is challenging, since most viscometers tend to use large volumes. We use short lengths of hollow-core photonic crystal fibres to determine the viscosity of small volumes of two types of monosaccharides diluted in a phosphate buffer solution. The simple optical technique used is based on the change in propagation characteristics of a laser beam travelling through the fibre as it fills with the nano-litre liquid of interest via capiliary action. The fiber length was kept in a temperature controlled casing, to minimize temperature differences across the fiber length for reproducibility and minimal error.