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BayWISS-Kolleg Ressource Efficiency and Materials www.baywiss.de

Neue Veröffentlichung: Sascha Schwarz Hochschule für angewandte Wissenschaften München

Preparation and mounting of the gelatin sample on the piezo actuator. a,The sample holder (blue) is fixed upside down on Parafilm (white)and held in place with adhesive tape (yellow).b,Liquid gelatin is pipetted into the cavity of the sample holder until a gelatin level of 3 mm is reached.c,After gelation of the sample, the sample holder is screwed directly onto the stack piezo (grey), and the Parafilm is removed.d,A visible pilot laser (green)is focused on the rim of the sample holder and measurement (red dots) and reference points (white dots) are defined on the gelatin sample and the sampleholder rim.

Contactless Vibrational Analysis of Transparent Hydrogel Structures Using Laser-Doppler Vibrometry

Schwarz, S.; Hartmann, B.; Sauer, J.; Burgkart, R.; Sudhop, S.; Rixen, D. J.; Clausen-Schaumann, H.

Abstract

Background

Investigating the mechanical properties of biological and biocompatible hydrogels is important in tissue engineering and biofabrication. Atomic force microscopy (AFM) and compression testing are routinely used to determine mechanical properties of tissue and tissue constructs. However, these techniques are slow and require mechanical contact with the sample, rendering in situ measurements difficult.

Objective

We therefore aim at a fast and contactless method for determining the mechanical properties of biological hydrogels and investigate if an optical method, like Laser-Doppler vibrometry (LDV), can accomplish this task.

Methods

LDV is a fast contactless method for mechanical analysis. Nonetheless, LDV setups operating in the visible range of the optical spectrum are difficult to use for transparent materials, such as biological hydrogels, because LDV relies on reflected or back-scattered light from the sample. We therefore use a near-infrared (NIR) scanning LDV to determine the vibration spectra of cylindrical gelatin discs of different gelatin concentration and compare the results to AFM data and unconfined compression testing.

Results

We show that the gelatin test structures can be analyzed, using a NIR LDV, and the Young’s moduli can be deduced from the resonance frequencies of the first normal (0,1) mode of these structures. As expected, the frequency of this mode increases with the square root of the Young’s modulus and the damping constant increases exponentially with gelatin concentration, which underpins the validity of our approach.

Conclusions

Our results demonstrate that NIR wavelengths are suitable for a fast, contactless vibrational analysis of transparent hydrogel structures.

 

https://doi.org/10.1007/s11340-020-00626-0

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Christian Gadelmeier

Christian Gadelmeier

Koordinator BayWISS-Verbundkolleg Ressourceneffizienz und Werkstoffe

Universität Bayreuth
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