Parallel-plate compression test for soft materials: confocal microscopy-assisted ferrule-top nanoindentation

The parallel-plate compression test is one of the simplest ways to measure the mechanical properties of a material. In this test, the Young's modulus ( $$ ) and the Poisson's ratio ( $$ ) of the material are determined directly without applying any additional modelling and parameter fitting in the post-processing. This is, however, limited when dealing soft biological materials due to their inherent properties such as being inhomogeneous, microscopic, and overly compliant. By combining an interferometry-assisted parallel-plate compression system and a confocal microscope, we were able to overcome these limitations and measure the $$ (315 $$ 52 Pa) and $$ (0.210 $$ 0.043) of fixated and permeabilized bovine oocytes.