Nucleation by Immersed Particle Instrument (NIPI)

The NIPI Suite

This wide range of efficiencies is accessed by using different droplet sizes. In the Pico-NIPI, picolitre droplets freeze at the lowest temperatures and in the Micro-NIPI, microlitre droplets freeze at the highest temperatures. The Micro-NIPI allows us to quantify the presence of rare particles which are very effective at nucleating ice and may be missed in other experiments.

Equipment

The NIPI suite is used to:

  • quantify nucleation by a range of atmospherically relevant particles - such as soot, desert dusts and biological materials - immersed in droplets
  • measure ice nucleation in natural samples, such as aerosols or sea water, taken from the environment
  • determine ice nucleation temperatures for use in cryopreservation.

Data provided by the NIPI have greatly improved our understanding of how clouds form from desert dusts. We have shown that feldspar is a far more important agent in nucleating ice than clay minerals, as previously thought. This study was published in Nature. The NIPI has also been used aboard the RRS James Clark Ross in a campaign to study ice nucleation in sea water samples in the Arctic.

IcePod

Our IcePod laboratory was most recently deployed to Barbados as part of the MarineIce research project which studies atmospheric ice-nucleating particles. The lab fits into a standard ISO 20' shipping container, making it ideal to be transported all over the world and operate in any environment.

Powder X-ray diffractometer

As well as standard ambient- and temperature-controlled stages, this instrument has a bespoke chamber which can be cooled to -195K and in which humidity can be controlled. It is used to study:

  • the properties of metastable ice which forms under atmospheric conditions,
  • the transformation of metastable ice to hexagonal ice,
  • the composition of mineral and desert and soil dusts and crystallisation of solution droplets.

Work with the Powder X-ray diffractometer has shown that what was known as cubic ice does not, in fact, have cubic symmetry. 'Stacking disordered ice' may be a more accurate name (PNAS 2012).

Raman microscope

The Raman microscope, with 785- and 514nm lasers, is equipped with a bespoke temperature- and humidity-controlled stage.Temperatures can be controlled from -80 to +50oC and humidities from dry to water saturation (i.e. 100% RH). We use this instrument to study:

  • diffusion coefficients in ultraviscous liquids and glassy aqueous solutions
  • phase changes in metastable solution droplets under conditions relevant to the atmosphere
  • crystallisation in acid solutions relevant for stratospheric clouds
  • the properties of single-celled organisms.

A new, prize-winning method of measuring diffusion coefficients has been developed using this microscope.

Who can use the facility?

We are committed to sharing our facilities and associated expertise with external academic and industrial collaborators. To make an enquiry please contact Professor Ben Murray, b.j.murray@leeds.ac.uk.