Department of Bioproducts and Biosystems

Biobased Materials Structure

The Biobased Materials Structure group, led by Academy of Finland Research Fellow Paavo Penttilä, focuses on structural characterization of biobased materials, especially with X-ray and neutron scattering. The group’s multidisciplinary expertise evolves around applying small and wide-angle X-ray and neutron scattering on wood and other (ligno)cellulosic materials. Understanding the structure of biobased materials and developing methods for their characterization is fundamental to their utilization for sustainable applications.
Colour photo of wood chips and samples on textured surfaces, in a petri dish and a closed test tube
Photo of wood samples by Research Fellow Paavo Penttilä

Research topics

  • Nanoscale structural characterization of biobased materials

  • Development of X-ray and neutron scattering data analysis

  • Wood nanostructure and moisture interactions

News and events

  • A major article "Nanoscale mechanism of moisture-induced swelling in wood microfibril bundles" from the SASAMIS project was published in Nano Letters, check also our post in the FinnCERES blog
  • Enriqueta joined the group as a new PhD student to work in the NNxWOOD project
  • Aleksi's first paper "Deswelling of microfibril bundles in drying wood studied by small-angle neutron scattering and molecular dynamics" appeared on the issue cover of Cellulose, read it here (open access)

Ongoing research projects

Neural networks for X-ray scattering analysis of wood materials (NNxWOOD)

Illustration of wood structure and anatomy cube, synchrotron, x-ray of wood, x-ray scattering data brought together with an AI "brain"

This Academy of Finland Research Fellow project (2021-2026) aims to develop new machine learning based methods for analysing X-ray scattering data from wood materials. A detailed picture of the structure of wood cell walls is highly desired to accelerate the development of new, sustainable applications from this abundant renewable raw material. Recently developed imaging techniques based on X-ray scattering offer unprecedented possibilities for studying the hierarchical structure of wood, but the development of new automated procedures for the data analysis is necessary.

Follow on Twitter: #NNxWOOD

Simulation-assisted scattering analysis of moisture-induced swelling in wood microfibril bundles (SASAMIS)

Illustration featuring Molecular models of microfibril bundles in brown and purple, to predict X-ray scattering patterns of wood samples, to refine the molecular models; line graph

The interpretation of X-ray scattering data from wood currently depends on highly approximate models of cellulose microfibrils and their bundles. By coupling molecular simulations with tailored scattering measurements, we can improve the resolving power of both methods, and gain fundamental information on the nanoscale structure and moisture behaviour of wood. This project is a collaboration between our group and VTT Technical Research Centre of Finland, funded by the FinnCERES Flagship of the Academy of Finland.

Related publications

Past research projects

Understanding the moisture behaviour of wood in nanoscale (WooD2O)

Illustration of Wide-angle X-ray scattering (WAXS): x-ray/neutrons into wood sample in a humidity chamber plus small-angle x-ray scattering (small-angle neutron scattering)

This postdoc project funded by the Academy of Finland (2018-2021) studied how the nanoscale structure of wood responds to moisture changes and how water is involved in the hierarchical structure of wood. The location of water inside of the wood cell wall and effects caused by moisture changes were studied especially using small-angle neutron and x-ray scattering.

Related publications

Follow on Twitter: #WooD2O

Comprehensive characterization of wood structure from nano- to mesoscale using small-angle neutron and X-ray scattering

Illustration and line graph showing cellulose microfibrils, a neutron beam, and a line graph of microfibrils, bundles, pores, WoosSAS dand SANS dat

This postdoc project, mainly funded by Emil Aaltonen foundation (2017-2018), developed small-angle scattering data analysis for wood samples. It resulted in the freely-available WoodSAS model, which can be used to analyse small-angle neutron and X-ray scattering (SANS, SAXS) data from wood.

Related publications


Paavo Penttilä

Paavo Penttilä

Academy Research Fellow
Department of Bioproducts and Biosystems
Photographic portrait of a person wearing glasses and a blue buttoned shirt smiling

Academy of Finland Research Fellow Paavo Penttilä

Dr. Penttilä graduated with a PhD from the University of Helsinki, Department of Physics in 2013, with a specialization in X-ray and neutron scattering. After spending in total four years as a postdoc at Kyoto University (Japan) and the Institut Laue-Langevin (France), he started as a postdoc at Aalto University in 2018. The Academy of Finland granted him Postdoctoral Researcher funding for 2018-2021, and then Research Fellow funding for 2021-2026. Dr. Penttilä holds the Title of Docent in Experimental Materials Physics, awarded by the University of Helsinki.

Doctoral Candidate Aleksi Zitting

I received my Master's degree in Physics from the University of Helsinki on molecular dynamics (MD) simulations of damage formation in fusion reactor materials in 2019. Starting from December 2019, I have been investigating wood-water interactions with scattering experiments and MD models, as a Doctoral Candidate concentrating on the experimental side of the SASAMIS project. The current focus of my studies is determining the nature of nanoscale structural changes due to moisture in wood cell walls using X-ray and neutron scattering.

Picture of Enriqueta

Doctoral Candidate Enriqueta Noriega Benitez

I studied space physics, including solar particle detection and simulations of such particles, at the University of Turku, where I received my Master's degree in Chemical and Physical Sciences in 2021. In February of 2022, I joined Paavo Penttilä’s research group at Aalto University in which we probe the structure of bio-based materials, chiefly wood, through the use of X-ray scattering techniques and machine learning algorithms. Currently, my work in the NNxWOOD project focusses on processing X-ray scattering data with an AI-based approach to analyze the nanostructure of wood.

How to join us?

Highly motivated MSc, doctoral or postdoctoral students interested in joining the group can contact Dr. Paavo Penttilä ([email protected]).


Illustration with three line graphs and SAXS/WAXS from wood, nanocellulose, colloidal particles, soft matter nanoassemblies etc.

Dr. Penttilä teaches the course “X-ray scattering methods for structural analysis of bio-based materials”, organised next time in April/May 2023. The target of the course is to introduce doctoral and advanced Master’s students to X-ray-based structural characterization methods (both in theory and in practice) and initiate the application of these methods in the students’ own research.


Our group has ongoing collaborations with researchers from Aalto University (Finland), VTT Technical Research Centre of Finland (Finland), University of Helsinki (Finland), Institut Laue‒Langevin (France), Kyoto University (Japan) and MAX IV Laboratory (Sweden).

Latest publications

Size-dependent filling effect of crystalline celluloses in structural engineering of composite oleogels

Mamata Bhattarai, Paavo Penttilä, Luisa Barba, Braulio Macias-Rodriguez, Sami Hietala, Kirsi S. Mikkonen, Fabio Valoppi 2022 LWT

Nanoscale Mechanism of Moisture-Induced Swelling in Wood Microfibril Bundles

Antti Paajanen, Aleksi Zitting, Lauri Rautkari, Jukka A. Ketoja, Paavo A. Penttilä 2022 Nano Letters

Effect of Moisture on Polymer Deconstruction in HCl Gas Hydrolysis of Wood

Tainise Lourençon, Michael Altgen, Timo Pääkkönen, Valentina Guccini, Paavo Penttilä, Eero Kontturi, Lauri Rautkari 2022 ACS Omega

Green Fabrication Approaches of Lignin Nanoparticles from Different Technical Lignins: A Comparison Study

Patrícia Figueiredo, Maarit Lahtinen, Melissa B. Agustin, Danila Morais de Carvalho, Sami-Pekka Hirvonen, Paavo Penttilä, Kirsi S. Mikkonen 2021 ChemSusChem

Combining scattering analysis and atomistic simulation of wood-water interactions

Paavo A. Penttilä, Antti Paajanen, Jukka A. Ketoja 2021 Carbohydrate Polymers

Water-accessibility of interfibrillar spaces in spruce wood cell walls

Paavo A. Penttilä, Aleksi Zitting, Tainise Lourençon, Michael Altgen, Ralf Schweins, Lauri Rautkari 2021 Cellulose

Directed Assembly of Cellulose Nanocrystals in Their Native Solid-State Template of a Processed Fiber Cell Wall

Iina Solala, Carlos Driemeier, Andreas Mautner, Paavo A. Penttilä, Jani Seitsonen, Miika Leppänen, Karl Mihhels, Eero Kontturi 2021 Macromolecular Rapid Communications

Deswelling of microfibril bundles in drying wood studied by small-angle neutron scattering and molecular dynamics

Aleksi Zitting, Antti Paajanen, Lauri Rautkari, Paavo A. Penttilä 2021 Cellulose

Experimental and Simulation Study of the Solvent Effects on the Intrinsic Properties of Spherical Lignin Nanoparticles

Tao Zou, Nonappa Nonappa, Mohammad Khavani, Maisa Vuorte, Paavo Penttilä, Aleksi Zitting, Juan José Valle-Delgado, Anna Maria Elert, Dorothee Silbernagl, Mikhail Balakshin, Maria Sammalkorpi, Monika Österberg 2021 Journal of Physical Chemistry B

Production of High Solid Nanocellulose by Enzyme-Aided Fibrillation Coupled with Mild Mechanical Treatment

Jaakko Pere, Tekla Tammelin, Piritta Niemi, Martina Lille, Tommi Virtanen, Paavo Penttilä, Patrik Ahvenainen, Stina Grönqvist 2020 ACS Sustainable Chemistry and Engineering
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