Bucknell University Mechanical & Chemical Engineering departments use ADMET’s eXpert 8000 Planar Biaxial testing system equipped with MTESTQuattro, an environmental bath, and the ADMET video extensometer for fibrous soft tissue (eg. skeletal muscle, tendon, meniscus) and engineered soft materials research. The main goals of these works are to better understand the structure-function mechanisms in biological soft tissues, particularly orthopaedic tissues, and to develop and design tissue replacements.
Benjamin Wheatley, PhD, the Principal Investigator of Bucknell University Mechanics and Modeling of Orthopaedic Tissues Laboratory, worked with ADMET to find a testing solution for him and his colleague Kenny Mineart, PhD. They were in search of an instrument that would be able to:
- Stretch samples to high strain (select polymeric gels remain elastic in excess of 1000% uniaxial strain)
- Measure a wide range of loads – from low (<1N) to mid (~1kN) while applying biaxial loading.
Dr. Wheatley’s research focuses on the characterization and simulation of the mechanical function of orthopaedic tissues, which are complex soft tissues that are fiber reinforced and saturated with fluids. Mechanical analyses and modeling approaches provide a better understanding of how these tissues function in the body, how diseases and impairment are linked, and how clinical treatments can be developed. The Laboratory’s emphasis is on skeletal muscle and its macro to micro level deformation. Questions that are addressed include; When skeletal muscle is deformed (such as stretching), how do the components of the tissue deform? How is the content and organization of skeletal related to muscle stiffness, particularly in impaired tissues? How does fluid flow in the tissue? This information can help shape broad engineering and clinical approaches. Click below to for the Laboratory website.
Dr. Mineart’s lab develops structure-function relationships in novel polymer gels, specifically physically-crosslinked gels. These polymeric gels are highly tunable in terms of their mechanical response including modulus and viscoelasticity, and thus are excellent candidates for a wide range of uses, including orthopaedic tissue replacement. Biaxial loading of the Laboratory’s polymeric gels provides the necessary data for more relevant and complex deformations enabling Dr. Mineart and his group to better understand their mechanical function and design gels for desired applications.
In one day, these teams are able to test a gel specimen that can stretch to 200+% equibiaxial strain, then very soft tissues such as skeletal muscle, and finally stiffer tissues such as tendon. This robustness was what these investigators valued the most, and is what the ADMET system was able to provide.
More from Dr. Wheatley:
“The ability to do all of the above is important to us. We strongly value having a range of load and displacement capabilities, along with a state-of-the-art digital image correlation system.
Here are some specific ways in which we use the data that we collect with the instrument:
- Correlate tissue structure to mechanics in orthopaedic tissues
- Develop and validate computational models of orthopaedic tissues
- Explore how polymeric gel formulation, and correspondingly nanostructure, affects gel mechanics”
Bucknell University testing system is a planar biaxial machine equipped with the MTESTQuattro controller and software. The system was supplied with multiple load cell capacities to allow a wide range of loads. Each load cell is calibrated per ASTM E4 to ensure +/-1% accuracy down to 0.5% of capacity.
The test frame includes an environmental bath with Nickel plated Stainless Steel grips and a heater and recirculating assembly as well as ADMET’s video extensometer and digital image correlation system (integrated with MTESTQuattro) for post-processing analyses such as minimum/maximum, mean and standard deviation, time-slice extraction, stress strain curve generation, data extraction along lines and more.
Non-contacting video based strain data with adjustable gauge lengths and extension ranges. The operator can measure single points or set multiple virtual extensometers. The extensometer provides real-time load vs. strain data with live output to MTESTQuattro for servo control. Video extensometer is capable of recording live data in both axial and transverse axis to provide data to calculate Poisson’s ratio.
The package contains algorithms to provide full-field displacement and strain data for mechanical testing on planar specimens and can be used for material testing including fracture mechanics, bi-axial tension tests, FEA validation such as strain localization around cracks and notches.
Video extensometer and DIC system include high-resolution monochrome digital camera, lens, lighting, mounts, and all required cables and adapters.
Click below for further information on planar biaxial testing or contact ADMET to discuss your testing application.