University of Oulu

Advanced imaging of lignocellulosic and cellulose materials

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Author: Ismail, Mostafa1,2,3
Organizations: 1University of Oulu Graduate School
2University of Oulu, Faculty of Technology, Process Engineering, Fibre and Particle Engineering (FPE)
3University of Oulu, Faculty of Science
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.4 MB)
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Language: English
Published: Oulu : University of Oulu, 2023
Publish Date: 2023-04-28
Thesis type: Doctoral Dissertation
Defence Note: Academic dissertation to be presented with the assent of the Doctoral Programme Committee of Technology and Natural Sciences of the University of Oulu for public defence in the Arina auditorium (TA105), Linnanmaa, on 5 May 2023, at 12 noon
Tutor: Professor Henrikki Liimatainen
Associate Professor Minna Patanen
Reviewer: Doctor Chithra Karunakaran
Professor Tekla Tammelin
Opponent: Professor Stephen Eichhorn


Lignocelluloses and their structural components are the most abundant biopolymeric materials. They are a renewable and biodegradable source for several applications (e.g., paper, packaging, and functional materials). Potential innovations related to lignocelluloses are foreseen both in the traditional product sectors such as packaging, hygiene, and tissue paper products, and multiple new areas, ranging from electronics to biomedicine. These innovations are based on novel forms of sustainable materials, such as nano- and microscale celluloses. For instance, nanocellulose films are tough, durable, and biodegradable. Their properties (e.g., mechanical strength and optical properties) can be altered when combined with functional fillers. Understanding the composition of lignocellulosic biomass and the structure of its different material designs is crucial for its efficient use. However, the material analysis of lignocelluloses is not straightforward; thus, easy-to-use analytical techniques are needed. Advanced imaging techniques offer appealing possibilities in lignocellulose analysis. This thesis aimed to investigate and understand various lignocellulose and cellulose materials, i.e., delignified wood fibers (thermomechanical pulp (TMP) fibers), tissue paper, and nanocellulose films, using advanced imaging techniques. The objective was to harness new techniques that can provide detailed information on the spatial distribution of material constituents and the structure and dynamics of physicochemical phenomena of materials derived from lignocelluloses. Fluorescence lifetime imaging tracked the delignification process based on a eutectic mixture and its effect on the TMP fiber characteristics, where it was found that cellulose poses fluorescent characteristics, and that lignin starts dissipating from the outer most layer of the fibers. The topography of tissue paper was tracked using noninvasive laser confocal microscopy, and measured the affect of the production on tissue paper’s softness. The morphology and chemical composition of hybrid nanocellulose films was measured in tandem using scanning transmission soft X-ray microscopy. The structure correlated to the mechanical properties, showing that agglomeration affects the mechanical behavior of the hybrid films at a certain point. Finally, the color change of thermochromic nanocellulose films was studied using optical microscopy and UV-vis spectroscopy, showing that the color change happens gradually in relation to temperature and humidity.

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Biomassat ja niiden johdannaiset, erityisesti selluloosa, ligniini ja hemiselluloosa (lignoselluloosat) ovat luonnon yleisimpiä biopolymeerejä, joita voidaan käyttää uusiutuvina ja biohajoavina raaka-aineina useissa sovelluksissa (esim. paperi-, ja pakkausmateriaaleissa ja funktionaalisissa kemikaaleissa). Fossiilisiin raaka-aineisiin liittyvien ympäristöongelmien vuoksi on tärkeää löytää uusiutuvia materiaaleja ja lisätä biopohjaisten vaihtoehtojen käyttöä. Lignoselluloosamateriaalien tutkimus ja niihin liittyvät innovaatiot ovat olennaisessa osassa ympäristön kannalta kestävien tuotteiden kehityksessä. Erilaiset kuvantamis- ja karakterisointimenetelmät ovat keskeisiä näiden materiaalien tutkimuksessa. Tässä väitöstyössä on keskitytty erityisesti kehittyneiden kuvantamismenetelmien soveltamiseen biomassapohjaisten lignoselluloosamateriaalien ja tuotteiden analysoinnissa. Työssä tutkittiin (ligno)selluloosamateriaalien, kuten puukuitujen (ns. TMP-kuiduttujen) delignifiointia uusilla vihreillä liuottimilla sekä pehmopaperituotteiden ja nanoselluloosakalvojen hienorakennetta ja kemiallisia ja fysikaalisia ominaisuuksia. Työn tulokset luovat perustaa biomassojen tutkimukselle kehittyneitä ja uudenaikaisia kuvantamistekniikoita käyttäen.

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Osajulkaisut / Original papers

Osajulkaisut eivät sisälly väitöskirjan elektroniseen versioon. / Original papers are not included in the electronic version of the dissertation.

  1. Ismail, M. Y., Sirviö, J. A., Ronkainen, V.-P., Patanen, M., Karvonen, V., & Liimatainen, H. (2022). Wood fibers delignified with eutectic mixture of carvacrol and methanosulfonic acid – Analysis of structure and fractional distribution of lignin, cellulose, and hemicellulose. Manuscript in preparation.

  2. Ismail, M. Y., Patanen, M., Kauppinen, S., Kosonen, H., Ristolainen, M., Hall, S. A., & Liimatainen, H. (2020). Surface analysis of tissue paper using laser scanning confocal microscopy and micro-computed topography. Cellulose, 27, 8989–9003.

    Rinnakkaistallennettu versio / Self-archived version

  3. Ismail, M. Y., Patanen, M., Sirviö, J. A., Visanko, M., Ohigashi, T., Kosugi, N., Huttula, M., & Liimatainen, H. (2019). Hybrid films of cellulose nanofibrils, chitosan and nanosilica—Structural, thermal, optical, and mechanical properties. Carbohydrate Polymers, 218, 87–94.

    Rinnakkaistallennettu versio / Self-archived version

  4. Karzarjeddi, M., Ismail, M. Y., Sirviö, J. A., Wang, S., Mankinen, O., Telkki, V.-V., Patanen, M., Laitinen, O., & Liimatainen, H. (2022). Adjustable hydro-thermochromic green nanofoams and films obtained from shapable hybrids of cellulose nanofibrils and ionic liquids for smart packaging. Chemical Engineering Journal, 443, 136369.

    Rinnakkaistallennettu versio / Self-archived version

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Series: Acta Universitatis Ouluensis. C, Technica
ISSN: 0355-3213
ISSN-E: 1796-2226
ISSN-L: 0355-3213
ISBN: 978-952-62-3646-9
ISBN Print: 978-952-62-3645-2
Issue: 875
Type of Publication: G5 Doctoral dissertation (articles)
Field of Science: 216 Materials engineering
Funding: The research documented in this thesis was conducted at the Fiber and Particle Engineering Research Unit at the University of Oulu between 2017 and 2021, funded by the European Union's Horizon 2020 Research and Innovation Program through the Marie Sklodowska-Curie grant agreement No. 713606. The author would also like to thank the Walter Ahlström Foundation for their support.
EU Grant Number: (713606) I4FUTURE - Novel Imaging and Characterisation Methods in Bio, Medical, and Environmental Research and Technology Innovations
Copyright information: © University of Oulu, 2023. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.