From left to right: Georg Schitter, Philipp Turner and Mathis Nalbach in the lab. Credit: Vienna University of Technology

Researchers from TU Wien have developed a new method suitable for mechanical tensile testing of micro- and nanofibers. Feature: samples can be reversibly connected to the power sensor and disconnected from it.

Experimental verification of the stiffness or tensile strength of fibers in the nano-microband often takes a very long time. Samples in most cases should be attached with glue at both ends. Curing of the adhesive takes time, and the sensor to which the fiber is glued cannot be reused.

Researchers from TU Wien, Mathis Nalbach, Philipp Turner and Georg Schitter, have developed a testing system that overcomes these obstacles. The principle of operation is as follows: the magnetic microsphere attached to the nanofiber can be picked up with magnetic tweezers. This allows you to insert a sphere into a fork attached to a power sensor and thus connected to the sensor. Since the magnetic sphere can also be removed from the fork with magnetic tweezers, other nanofibers can be picked up immediately. This greatly increases the sampling throughput. Recently, researchers presented in the journal the NanoTens tensile tester Review of scientific instruments.

Adapted to real conditions

While atomic force microscope can be used for study mechanical properties fibers using a nanopermeability test, NanoTens allows you to test the material for the presence of fibers at a more appropriate tensile load. Philip Turner of the Biomechanics Research Department explains how it works: “You can think of a device as a microscopic loader. A magnetic ball that is glued to a fiber is inserted into a fork. By moving the fork up or down, the fiber can now be tested under tensile load. It is particularly relevant for biological fibers, such as collagen fibrils. Physiologically, they are mainly loaded by stretching, and therefore their mechanical properties are particularly important at this load. “

Biomechanics Nalbach and Turner mainly study natural fibers such as collagen. Because their mechanical properties are highly dependent on external conditions, they are also important to consider when testing for tension. “We did it because NanoTens can be used for tensile tests in different environments. For example, dry collagen fiber is much more fragile and stiff than wet or fully moistened. Its diameter is also greatly reduced when dried,” says Mathis Nalbach. , the first author of the study.

Quality and quantity increase

With their method, the researchers not only succeed in modeling physiological conditions, but the results obtained with NanoTens are also authentic. This is because a large number of measurements are required to obtain significant results biological materials for example, collagen fibrils. “Conventional methods only allow you to study one or two samples a week. This makes it virtually impossible to conduct statistically significant research, ”Nalbach describes. Philip Turner adds: “The new method allows you to quickly connect and disconnect the fibers. As a result – and because the sensor is reused – we can not only increase the number of tensile tests to 50 measurements per week, but also the accuracy of measurements.”

Tensile tests can – depending on the choice – be carried out in a wide range of efforts and controlled by a control system. This is important because tensile test methods typically assume that the material has linear-elastic properties. However, this is not the case with biological tissues such as collagen fibrils: they are viscoelastic. The tensile test with controlled force allows to study this viscoelasticity.

From invention to product

NanoTens has already been an internationally patented TU Wien. “The next step will be to join forces with industry partners. We hope to find a licensee through research and transfer support. We are interested in collaborating with industry on this topic,” says Mathis Nalbach. NanoTens is designed in such a way that it can usually be integrated into any device for measuring indentations or an atomic force microscope. In addition to materials sciencetensile testing is also used – among other things – in the life sciences, semiconductor technology and electronics.

Numerical simulation of erythrocyte stretching tests

Additional information:
Mathis Nalbach et al., Device for tensile testing of individual collagen fibrils with easy connection and detachment of samples, Review of scientific instruments (2022). DOI: 10.1063 / 5.0072123

Citation: A new method for mechanical tensile testing of micro- and nanofibers (May 24, 2022), obtained May 24, 2022 from .html

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