Direct Comparison of Three Buckling-Based Methods to Measure the Elastic Modulus of Nanobiocomposite Thin Films

To engineer tunable thin-film materials, the accurate measurement of their mechanical properties is crucial. However, characterizing elastic modulus with current methods particularly challenging for sub-micrometer thick films and hygroscopic materials because they are highly sensitive to environmental conditions most require free-standing which difficult prepare. In this work, we directly compared three buckling-based determine moduli supported thin films: (1) biaxial thermal shrinking, (2) uniaxial (3) mechanically compressed, strain-induced buckling instability measurements (SIEBIMM) method. Nanobiocomposite model composed cellulose nanocrystals (CNCs) polyethyleneimine (PEI) were assembled using layer-by-layer deposition control composition thickness. The yielded same trends comparable values each CNC-PEI film (ranging from 15 44 GPa, depending on composition). This suggests that similarly effective quantification properties. Increasing CNC content in statistically increased modulus; however, increasing PEI did not lead significant changes. For system, standard deviation determined SIEBIMM was 2-4 times larger than likely due extensive cracking different stress applied when subjected compression a relaxed substrate versus shrinking pre-strained substrate. These results show reliable method determination simple implementation analysis low sensitivity small deviations input parameter values, such as thickness or modulus.