To engineer tunable thin film materials, accurate measurement of their mechanical properties is

crucial. However, characterizing the elastic modulus with current methods is particularly

challenging for sub-micrometer thick films and hygroscopic materials because they are highly

sensitive to environmental conditions and most methods require free-standing films which are

difficult to prepare. In this work, we directly compared three buckling-based methods to determine

the elastic moduli of supported thin films: 1) biaxial thermal shrinking, 2) uniaxial thermal

shrinking, and 3) the mechanically compressed, strain-induced elastic buckling instability for

mechanical measurements (SIEBIMM) method. Nanobiocomposite model films composed of

cellulose nanocrystals (CNCs) and polyethyleneimine (PEI) were assembled using layer-by-layer

deposition to control composition and thickness. The three buckling-based methods yielded the

same trends and comparable values for the elastic moduli of each CNC-PEI film composition

(ranging from 15 – 44 GPa, depending on film composition). This suggests that the methods are

similarly effective for the quantification of thin film mechanical properties. Increasing the CNC

content in the films statistically increased the modulus, however, increasing the PEI content did

not lead to significant changes. The standard deviation of elastic moduli determined from

SIEBIMM was 2-4 times larger than for thermal shrinking, likely due to extensive cracking and

partial film delamination. In light of these results, biaxial thermal shrinking is recommended as

the method of choice because it affords the simplest implementation and analysis and is the least

sensitive to small deviations in the input parameter values, such as film thickness or substrate

modulus.

为了设计可调谐薄膜材料，需要对其机械性能进行准确的测量

关键。然而，用当前方法表征弹性模量尤其重要

亚微米厚膜和吸湿性材料具有很高的挑战性

对环境条件敏感，大多数方法都需要独立的胶片

很难准备。在这项工作中，我们直接比较了三种基于屈曲的方法来确定

支撑薄膜的弹性模量：1）双轴热收缩，2）单轴热收缩

收缩； 3）机械压缩，应变引起的弹性屈曲不稳定性

机械测量（SIEBIMM）方法。纳米生物复合模型膜组成

纤维素纳米晶体（CNC）和聚乙烯亚胺（PEI）使用逐层组装

沉积以控制成分和厚度。三种基于屈曲的方法得出了

每种CNC-PEI膜组合物的弹性模量具有相同的趋势和可比较的值

（范围从15 – 44 GPa，取决于膜的组成）。这表明方法是

对量化薄膜机械性能同样有效。增加CNC

薄膜中的PEI含量统计上增加了模量，但是增加PEI含量确实

不会导致重大变化。弹性模量的标准偏差由

SIEBIMM比热收缩大2-4倍，这可能是由于大量开裂和

薄膜部分分层。根据这些结果，建议采用双轴热收缩

选择方法，因为它提供了最简单的实现和分析，并且最少

对输入参数值的微小偏差敏感，例如薄膜厚度或基材

模量。