Ultrasonic Setup for Testing Hydrogels: Preliminary Experiments on Collagen Gels

Abstract

The assessment of mechanical properties of highly hydrated natural materials remains a challenge because, in general, their mechanical evaluation implies invasive and finally destructive methods. Acoustic-based tests may represent the appropriate tools to investigate the mechanical properties of such materials, particularly collagen gels, whose acoustic properties are poorly understood. The objective of this work is to develop two experimental setups for the assessment of acoustic properties of such a hydrogels. In the first one, a typical pulse echo reflectometer was implemented. The acoustic parameters were measured at controlled temperature in an especially designed chamber. In the second one, the previous configuration was combined with a setup for compressive tests, allowing to interrogate simultaneously both the acoustic and mechanical properties of the sample under test. The frequency of the acoustic transducer was 10MHz. The acoustic and mechanical properties of collagen gels prepared according to different experimental conditions (pH and collagen concentration) were evaluated. The first set of experiment was useful to accomplish estimation of the speed of sound, attenuation and acoustic impedance. The second one allowed us to monitor the speed of sound during the evolution of the compression test. This approach could be a potential tool to study the changes in hydrogels mass density and bulk compressibility.