Moisture and Microscopy – Guest Blog from Surface Measurement Systems Ltd

Jan Gorgol, Product Manager at Surface Measurement Systems Ltd based in London has put together an interesting blog on the impact of moisture on modern microscopy. We hope you like it! 

Moisture affects a huge range of materials in very broad industries and research areas.

One of many tools used in characterising moisture effects is Microscopy , ranging from light microscopy including dark-field, light field or cross-polarisation to Raman or FTIR microscopy’s and more esoteric imaging techniques such as Atomic Force Microscopy , 3D X-Ray Tomography or PAM.

Some of the diverse areas where different kinds of microscopy can be effectively used to study the effects of moisture and humidity on real life situations include:

Pharmaceutical

  • Studies of crystallisation of amorphous samples under humidification including hydration of stable and unstable hydrates, deliquescence and liquefaction of hygroscopic samples, co-crystallisation and solvate desorption at high humilities.
  • Polarized light microscopy and birefringence can be used effectively to study Crystal morphological growth. Polymorphism can be studied by Raman, FTIR, and light microscopy. [1]
Light microscopy of PVP drug carrier showing welling and Coalescence at humidity
Light microscopy of PVP drug carrier showing welling and Coalescence at humidity

Cosmetics

  • Hair colour, pigmentation, thickness, tensile strength, shape, decomposition and effects of hair products have been studied with Light and Raman Microscopies.

Paper and environment

  • Polarised light microscopy can be used to study Sludge and dry solids from paper mill residues for evaluation of recovery of wood fibres, pigments, and other paper additives.
  • Polarised light microscopy is also effective in Biodegradable fibres decomposition studies.

Wood

  • Characterisation of wood and vegetable fibre pigments using FTIR and Light microscopy
  • Studies of wood swelling in 3D using X-ray tomography.
  • Studies of effects of humidity on wood adhesive coatings using AFM

Food

  • Effects of humidity on flowability of lactose due to changing amorphous and crystalline content using Raman and light microscopy.
Light microscopy of Amorphous Lactose Crystallisation with humidification
Light microscopy of Amorphous Lactose Crystallisation with humidification
  1. a) Surface adsorption 0% RH
    b) Bulk absorption &surface adsorption 50%RH
    c) Recrystallisation 60%RH
    d) Crystalline Material 90%RH
  • Moisture Induced Phase Transitions of food flavouring studied by light microscopy.
  • Moisture content of seeds has been studied using photo acoustic microscopy helping sustainable agriculture development.
Sucrose crystals at 200X at 95%RH
Sucrose crystals at 200X at 95%RH
  • Effects of humidity on dry milk powders measured using light microscopy [2]
Photographs of Milk powder at 64%, 81% and 85% RH
Photographs of Milk powder at 64%, 81% and 85% RH

Optical coatings

  • Use of phase interference contrast microscopy to study Degradation of anti-reflective optical coatings due to delimitation

Fibres

  • Study of humidity related swelling of wool & cotton fibres using scanning probe microscopy
Tissue paper showing fibre orientation and weave pattern at 95%%RH 200X
Tissue paper showing fibre orientation and weave pattern at 95%%RH 200X

Biological

  • Effects of Humidity and CO2 in live cell imaging incubators

Bacteria

  • Effects of humidity on morphology and elastic properties of Bacteria using AFM

Minerals and Rock

  • Raman Microscopy has been used to study phase changes in Portland cement

Building Materials

  • Critical humidity control in microscopy of microcracked slag materials
  • Slab curing studies related to moisture sensitive floor covering such as wood, PVC, rubber backed carpets,lino and related effects such as delamination, peeling, blistering, staining, etc

These are just a few areas where microscopy can be valuably used to study the effects of changing humidity on real life sample. To help meet Scientists and Technician’s many needs in these areas Surface Measurement Systems have developed an environmental microscopy cell GenRH-Mcell [3] to enable precise critical humidity Microscopy studies in situ.The RH probe chosen for this cell was supplied by Rotronic based on its accuracy, small footprint and excellent quality.

Please feel welcome to contact me jgorgol@surfacemeasurementsystems.com if you have any humidity generation needs in such areas or are interested in adding critical humidity control to other analytical techniques such as DMA,TGA,DSC,XRD, contact angle or process control areas, sample conditioning, mechanical or tensile testing, rheology, powder flow, and so on. Overview of such applications at http://surfacemeasurementsystems.com/products/genrh-family/product-presentation/

References
[1] Dependence of cocrystal formation and thermodynamic stability on moisture sorption by amorphous polymer. David Good,   Crystal Miranda and   Naír Rodríguez-Hornedo
CrystEngComm, 2011,13, 1181-1189
[2] SurfaceMeasurementSystems Application Note 503 – Investigating Dried Milk Powders Using Optical Microscopy at Different Humidity Conditions.
[3] SurfaceMeasurementSystems Application Note 501 – Environmental Microscopy using the GenRH-A Humidity Generator and Mcell Accessory.

About the author:
Jan Gorgol studied Physics at Bristol University followed by a Masters at Brunel University while running XPS & SEM at the Experimental Techniques Centre. After working extensively in Surface science instrumentation globally he now is Product Manager for the GenRH series of humidity generation products at Surface Measurement Systems Ltd.

Related Article blogs:
1. Formulation, Microscopy and Moisture

2.http://surfacemeasurementsystems.com/applications/microscopy-and-moisture/

Interested in sharing a blog? Please contact us!

Dr Jeremy Wingate
Rotronic Instruments (UK) Ltd
jeremyw@rotronic.co.uk

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