Utilization of 3D printing technology to facilitate and standardize soft tissue testing

Mario Scholze,Pamela F Lozano,Niels Hammer,Michael Werner,Aqeeda Singh,Benjamin Ondruschka,Maziar Ramezani

doi:10.1038/s41598-018-29583-4

Abstract

Three-dimensional (3D) printing has become broadly available and can be utilized to customize clamping mechanisms in biomechanical experiments. This report will describe our experience using 3D printed clamps to mount soft tissues from different anatomical regions. The feasibility and potential limitations of the technology will be discussed. Tissues were sourced in a fresh condition, including human skin, ligaments and tendons. Standardized clamps and fixtures were 3D printed and used to mount specimens. In quasi-static tensile tests combined with digital image correlation and fatigue trials we characterized the applicability of the clamping technique. Scanning electron microscopy was utilized to evaluate the specimens to assess the integrity of the extracellular matrix following the mechanical tests. 3D printed clamps showed no signs of clamping-related failure during the quasi-static tests, and intact extracellular matrix was found in the clamping area, at the transition clamping area and the central area from where the strain data was obtained. In the fatigue tests, material slippage was low, allowing for cyclic tests beyond 105 cycles. Comparison to other clamping techniques yields that 3D printed clamps ease and expedite specimen handling, are highly adaptable to specimen geometries and ideal for high-standardization and high-throughput experiments in soft tissue biomechanics.

Highlights

Standardization of mechanical experiments involving biological soft tissues when tested under strain remains an ongoing issue with negative impact on the accuracy and validity
We aimed to explore alternative techniques which may facilitate tissue clamping, and aid in standardizing the clamping of soft tissues for biomechanical testing in a less time-consuming manner. 3D printing has become broadly available, and such professional extrusion solutions can be utilized for customizing and printing fixtures and adjustments for biomechanical testing using commercially-available filaments
polylactic acid (PLA) was primarily used for the tables, templates and clamps, and thermoplastic polyurethane (TPU) for the specimensmounting frame, which consisted of two supporting arms

Summary

Introduction

Standardization of mechanical experiments involving biological soft tissues when tested under strain remains an ongoing issue with negative impact on the accuracy and validity. To obtain robust results, large sample sizes are necessary to outweigh the statistical scatter which is likely to occur To overcome issues such as material slippage in uniaxial tensile tests, a number of adjustments and fixtures have been introduced[1,2,3], including steel clamps with roughed surface areas[4,5] and high friction areas[6,7,8,9], cryogenic clamps[10,11] or pneumatic clamps[1,2,3,9,12,13,14]. The feasibility and potential limitations of the technology will be discussed, and two scenarios will be shown for quasi-static and cyclic (fatigue) tests

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Conclusion