Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Natural nanofibres made of cellulose

19.12.2018

Kiel research team discovers strongly-adhesive nanofibres in the mucous sheath of plant seeds

The seeds of some plants such as basil, watercress or plantain form a mucous envelope as soon as they come into contact with water. This cover consists of cellulose in particular, which is an important structural component of the primary cell wall of green plants, and swelling pectins, plant polysaccharides.


Through contact with water, the seed of Neopallasia pectinata from the family of composite plants forms a slimy sheath. The white cellulose fibres anchor it to the seed surface.

© Kreitschitz


A detailed view under the microscope shows cellulose fibres on the surface of a seed of Artemisia leucodes from the family of composite plants. The actually colourless fibres were coloured purple for better visibility.

© Kreitschitz

In order to be able to investigate its physical properties, a research team from the Zoological Institute at Kiel University (CAU) used a special drying method, which gently removes the water from the cellulosic mucous sheath.

The team discovered that this method can produce extremely strong nanofibres from natural cellulose. In future, they could be especially interesting for applications in biomedicine. The team’s results recently appeared as the cover story in the journal Applied Materials & Interfaces.

Thanks to their slippery mucous sheath, seeds can slide through the digestive tract of birds undigested. They are excreted unharmed, and can be dispersed in this way. It is presumed that the mucous layer provides protection.

"In order to find out more about the function of the mucilage, we first wanted to study the structure and the physical properties of this seed envelope material," said Zoology Professor Stanislav N. Gorb, head of the "Functional Morphology and Biomechanics" working group at the CAU. In doing so they discovered that its properties depend on the alignment of the fibres that anchor them to the seed surface.

Diverse properties: From slippery to sticky

The pectins in the shell of the seeds can absorb a large quantity of water, and thus form a gel-like capsule around the seed in a few minutes. It is anchored firmly to the surface of the seed by fine cellulose fibres with a diameter of just up to 100 nanometres, similar to the microscopic adhesive elements on the surface of highly-adhesive gecko feet. So in a sense, the fibres form the stabilising backbone of the mucous sheath.

The properties of the mucous change, depending on the water concentration. "The mucous actually makes the seeds very slippery. However, if we reduce the water content, it becomes sticky and begins to stick," said Stanislav Gorb, summarising a result from previous studies together with Dr Agnieszka Kreitschitz. The adhesive strength is also increased by the forces acting between the individual vertically-arranged nanofibres of the seed and the adhesive surface.

Specially dried

In order to be able to investigate the mucous sheath under a scanning electron microscope, the Kiel research team used a particularly gentle method, so-called critical-point drying (CPD). They dehydrated the mucous sheath of various seeds step-by-step with liquid carbon dioxide - instead of the normal method using ethanol.

The advantage of this method is that evaporation of liquid carbon dioxide can be controlled under certain pressure and temperature conditions, without surface tension developing within the sheath. As a result, the research team was able to precisely remove water from the mucous, without drying out the surface of the sheath and thereby destroying the original cell structure. Through the highly-precise drying, the structural arrangement of the individual cellulose fibres remained intact.

Almost as strongly-adhesive as carbon nanotubes

The research team tested the dried cellulose fibres regarding their friction and adhesion properties, and compared them with those of synthetically-produced carbon nanotubes. Due to their outstanding properties, such as their tensile strength, electrical conductivity or their friction, these microscopic structures are interesting for numerous industrial applications of the future.

"Our tests showed that the frictional and adhesive forces of the cellulose fibres are almost as strong as with vertically-arranged carbon nanotubes," said Dr Clemens Schaber, first author of the study. The structural dimensions of the cellulose nanofibers are similar to the vertically aligned carbon nanotubes.

Through the special drying method, they can also vary the adhesive strength in a targeted manner. In Gorb’s working group, the zoologist and biomechanic examines the functioning of biological nanofibres, and the potential to imitate them with technical means.

"As a natural raw material, cellulose fibres have distinct advantages over carbon nanotubes, whose health effects have not yet been fully investigated," continued Schaber. Nanocellulose is primarily found in biodegradable polymer composites, which are used in biomedicine, cosmetics or the food industry.

Photos are available to download:
https://www.uni-kiel.de/de/pressemitteilungen/2018/431-Samen-1.jpg
Caption: Through contact with water, the seed of Neopallasia pectinata from the family of composite plants forms a slimy sheath. The white cellulose fibres anchor it to the seed surface.
© Kreitschitz

https://www.uni-kiel.de/de/pressemitteilungen/2018/431-Samen-2.jpg
Caption: A detailed view under the microscope shows cellulose fibres on the surface of a seed of Artemisia leucodes from the family of composite plants. The actually colourless fibres were coloured purple for better visibility.
© Kreitschitz

https://www.uni-kiel.de/de/pressemitteilungen/2018/431-Samen-3.jpg
Caption: With their study, the Kiel research team made it onto the cover of the international journal Applied Materials & Interfaces.
© (2018) American Chemical Society.

https://www.uni-kiel.de/de/pressemitteilungen/2018/431-Samen-4.jpg
Caption: Zoologist and biomechanic Clemens Schaber investigates biological nanofibres at Kiel University, in order to imitate them with technical means.
© Julia Siekmann, CAU

Wissenschaftliche Ansprechpartner:

Professor Stanislav N. Gorb
Zoological Institute at Kiel University

Tel.: +49 (0)431/880-4513

E-mail: sgorb@zoologie.uni-kiel.de
Website: http://www.uni-kiel.de/zoologie/gorb/topics.html

Dr. Clemens Schaber
Tel. +49 431 880-4509
Mail: cschaber@zoologie.uni-kiel.de

Originalpublikation:

Original publication:
Friction-Active Surfaces Based on Free-Standing Anchored Cellulose Nanofibrils. Clemens F. Schaber, Agnieszka Kreitschitz, and Stanislav N. Gorb
ACS Applied Materials & Interfaces 2018 10 (43), 37566-37574
DOI: 10.1021/acsami.8b05972, https://pubs.acs.org/doi/10.1021/acsami.8b05972

Weitere Informationen:

https://www.uni-kiel.de/en/details/news/samen0/

Dr. Boris Pawlowski | Christian-Albrechts-Universität zu Kiel

More articles from Life Sciences:

nachricht OHIO professor Hla develops robust molecular propeller for unidirectional rotations
22.08.2019 | Ohio University

nachricht In cystic fibrosis, lungs feed deadly bacteria
22.08.2019 | Columbia University Irving Medical Center

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Physicists create world's smallest engine

Theoretical physicists at Trinity College Dublin are among an international collaboration that has built the world's smallest engine - which, as a single calcium ion, is approximately ten billion times smaller than a car engine.

Work performed by Professor John Goold's QuSys group in Trinity's School of Physics describes the science behind this tiny motor.

Im Focus: Quantum computers to become portable

Together with the University of Innsbruck, the ETH Zurich and Interactive Fully Electrical Vehicles SRL, Infineon Austria is researching specific questions on the commercial use of quantum computers. With new innovations in design and manufacturing, the partners from universities and industry want to develop affordable components for quantum computers.

Ion traps have proven to be a very successful technology for the control and manipulation of quantum particles. Today, they form the heart of the first...

Im Focus: Towards an 'orrery' for quantum gauge theory

Experimental progress towards engineering quantized gauge fields coupled to ultracold matter promises a versatile platform to tackle problems ranging from condensed-matter to high-energy physics

The interaction between fields and matter is a recurring theme throughout physics. Classical cases such as the trajectories of one celestial body moving in the...

Im Focus: A miniature stretchable pump for the next generation of soft robots

Soft robots have a distinct advantage over their rigid forebears: they can adapt to complex environments, handle fragile objects and interact safely with humans. Made from silicone, rubber or other stretchable polymers, they are ideal for use in rehabilitation exoskeletons and robotic clothing. Soft bio-inspired robots could one day be deployed to explore remote or dangerous environments.

Most soft robots are actuated by rigid, noisy pumps that push fluids into the machines' moving parts. Because they are connected to these bulky pumps by tubes,...

Im Focus: Vehicle Emissions: New sensor technology to improve air quality in cities

Researchers at TU Graz are working together with European partners on new possibilities of measuring vehicle emissions.

Today, air pollution is one of the biggest challenges facing European cities. As part of the Horizon 2020 research project CARES (City Air Remote Emission...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

The power of thought – the key to success: CYBATHLON BCI Series 2019

16.08.2019 | Event News

4th Hybrid Materials and Structures 2020 28 - 29 April 2020, Karlsruhe, Germany

14.08.2019 | Event News

What will the digital city of the future look like? City Science Summit on 1st and 2nd October 2019 in Hamburg

12.08.2019 | Event News

 
Latest News

OHIO professor Hla develops robust molecular propeller for unidirectional rotations

22.08.2019 | Life Sciences

127-year-old physics problem solved

22.08.2019 | Physics and Astronomy

Physicists create world's smallest engine

22.08.2019 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>