Determination of the Ignorable Boundary Condition and Standard Sample for A Novel in-situ Dynamic Mechanical Analysis Method on Soft Matter

TL;DR

This paper establishes the optimal size for a standard soft matter sample in in-situ DMA testing to minimize boundary effects, validated through finite element analysis and experimental testing on silicone gels.

Contribution

It introduces a method to determine the standard sample size for in-situ DMA of soft matter, ensuring boundary effects are negligible, which was previously unaddressed.

Findings

Optimal sample size identified as 40mm x 40mm x 20mm

Finite element analysis validated by experimental tests

Material properties of silicone gel closely mimic biological tissue

Abstract

An in-situ Dynamic Mechanical Analysis (DMA) method for soft matter developed by our group [Wu. et.al. 2022] encounters the problem of irregular samples, which significantly vary in shape and size in practice, therefore a standard sample "large enough" to ignore the boundary and size effects is necessary to determine the baseline of test and build the correspondence between this new method to classical mechanical tests. In this work, we use finite element analysis to approach the optimal size of a brick sample where the stress on the boundaries in three spatial directions are ignorable, and certified the results by testing a series of silicone gel samples on the in-situ DMA device. The stress-strain of tensile and compression are characterized. The material properties of gel are chosen to be close to the biological soft tissue. The size of 40mm(L)*40mm(W)*20mm(H) is determined to be the optimal result.