Development of Novel In Situ Microscopy Techniques for the Study of Water Interaction with Soft Materials
Doktorsavhandling, 2014

The transport of water in soft materials can occur in liquid or gas phase and is highly dependent on the material microstructure and the structure dynamics. Understanding these relationships is the basis for the development of predictive models that can aid the design of new and improved functional materials. The environmental scanning electron microscope (ESEM) enables the visualisation of the effects of hydration or dehydration on a specimen down to the nanometre scale, facilitating the understanding of the structure-property relationships. However, the full potential of the ESEM has not yet been explored, especially when it comes to the transport of water in materials. The aim of this work was to develop new ESEM-based methods that enable the in situ study of water interaction with soft materials in a controlled manner. We designed a sample stage that uses a manipulator to bring the specimen in contact with a water reservoir in the ESEM, rendering the point of contact between water and specimen available for visual studies. In addition, coupled with a piezoresistive atomic force microscopy (AFM) sensor, the setup enables the local measurement of displacements in the nanometre range with millisecond temporal resolution through force spectroscopy. Thus, it provides a sensitive probe for swelling, which is an important effect of the water interaction for many soft materials. The potential of the developed methods has been demonstrated on three different materials systems and geometries. The absorption and transport of liquid water in individual cellulose fibres were imaged for the first time. The volumes of absorbed droplets were typically in the range of 0.02 nL to 0.2 nL and the rate of absorption varied between different fibres. The method was also applied to phase-separated polymer films intended as controlled-release coatings in oral pharmaceutical formulations and enabled the first studies of the water interaction in the initial stage of wetting. Simultaneous probing of the microstructure and the local water transport properties of the films provided previously inaccessible information about the structure-transport relationships and the microstructural evolution caused by the water interaction. In addition, measurements of the time-dependent osmotic swelling of yeast cells in the ESEM were demonstrated with a high spatial and temporal resolution. This type of measurement is valuable for the understanding of the water transport properties of cell membranes. The versatility of the setup allows the technique to be applied to a wide range of different materials systems and geometries where the interaction with water is of interest.

in situ

environmental scanning electron microscopy

osmotic shock

water transport

swelling

water interaction

manipulator

cellulose fibre

yeast cell

polymer film

Euler, Skeppsgränd 3, Chalmers tekniska högskola, 41296 Göteborg
Opponent: Prof. Bradley Thiel, College of Nanoscale Science and Engineering, University at Albany, State University of New York, USA

Författare

Anna Olsson

SuMo Biomaterials

Chalmers, Teknisk fysik, Eva Olsson Group

Novel Method for Controlled Wetting of Materials in the Environmental Scanning Electron Microscope

Microscopy and Microanalysis,; Vol. 19(2013)p. 30-37

Artikel i vetenskaplig tidskrift

Monitoring the osmotic response of single yeast cells through force measurement in the environmental scanning electron microscope

Measurement Science and Technology,; Vol. 25(2014)p. Art. no. 025901-

Artikel i vetenskaplig tidskrift

Novel Method for Visualizing Water Transport Through Phase-Separated Polymer Films

Microscopy and Microanalysis,; Vol. 20(2014)p. 394-406

Artikel i vetenskaplig tidskrift

I vår vardag möter vi många typer av material vars funktion är kopplad till deras växelverkan med vatten. Ett exempel är pappersprodukter som ska kunna absorbera och transportera vätska snabbt och effektivt; ett annat är läkemedel i tablettform, där frisättningen av den aktiva ingrediensen bestäms av hur formuleringen löses upp i kontakt med vatten i kroppen. Även i våra celler är vattentransport viktigt, då många kritiska funktioner kräver att cellens vatteninnehåll kan regleras med hjälp av cellmembranets genomsläpplighet. Alla dessa egenskaper är starkt beroende av materialens mikrostruktur. Hos mjuka material vars struktur förändras genom kontakt med vatten blir förhållandet mellan struktur och egenskaper komplext. Detta arbete syftar till att skapa nya experimentella metoder som kan öka förståelsen genom att visualisera materialens växelverkan med vatten. Vi har utvecklat en provhållare som kan användas inuti ett elektronmikroskop och som möjliggör dynamiska experiment under avbildning. Detta ger information om mikrostruktur och egenskaper på liten skala samtidigt. Tekniken är flexibel och kan användas för prover med olika geometri. Med hjälp av en känslig sensor kopplad till utrustningen kan man även göra noggranna mätningar av svällning i en fuktig miljö. Vi har använt tekniken för att studera olika material och visat att den kan ge ny och viktig information som bidrar till utvecklingen av framtida förbättrade material med nya funktioner.

Everyday, we surround ourselves with functional materials whose performance depends on the interaction with water. For example, many paper products rely on fast and efficient water absorption and transport, and the release of drugs from oral pharmaceuticals is governed by the swelling and dissolution of the formulation by water in the body. Furthermore, living cells depend crucially on the water transport properties of the cell membrane, which enable regulation of the cell volume. These properties are all strongly influenced by the materials’ microstructure. For soft materials whose structure changes through contact with water, the relationships between structure and properties are complex. The aim of this work is to create new experimental methods that can increase the understanding of these relationships by visualising the interaction between materials and water. We have developed a sample stage that can be used inside an electron microscope to enable dynamic experiments while imaging. This provides simultaneous information about microstructure and properties at small length scales. The technique is flexible and can be used for samples with different geometry. Coupled with a sensitive probe, the setup can also be used to measure swelling in a humid environment with high accuracy. We have used the technique to study different materials and shown that it can provide important new information contributing to the development of future materials with improved functionality.

Ämneskategorier

Annan teknik

Biomaterialvetenskap

Den kondenserade materiens fysik

Styrkeområden

Materialvetenskap

ISBN

978-91-7597-120-9

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie

Euler, Skeppsgränd 3, Chalmers tekniska högskola, 41296 Göteborg

Opponent: Prof. Bradley Thiel, College of Nanoscale Science and Engineering, University at Albany, State University of New York, USA