Originally Published EMDM
September 2004
Technology News
Tensile Tester Handles Minute Samples of Elastic MaterialsNorbert Sparrow
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| A tester that was initially developed to measure the elasticity of eye tissue can be used to perform tensile tests on a range of elastic materials. |
Advanced material testing often requires the use of small samples. HumanOptics AG (Erlangen, Germany) has developed a tensile tester that precisely measures the mechanical properties of minute quantities of biomaterials and human tissues. The firm, whose core activity is the production of ocular implants, initially developed the machine to measure the elasticity of eye tissue.
“We were working with a university institute to develop a biomechanical model of the eye,” says engineer Tim Use. “We had the geometrical parameters, which we put into a 3-D CAD program. But we also needed to determine the eye tissue’s mechanical properties. That’s why we built this machine.” It soon became apparent that the device had some broader applications.
The 2-N-capacity system features 20-µN resolution. The short 15-mm displacement mechanism has 2-nm resolution. An integrated air bearing lessens friction in the moving parts. The device is suited for a variety of material testing tasks in R&D and quality assurance.
The unit can be used for deformation and measurement tests, says Use. Specimens suspended in liquid or air can also be tested. High-resolution microscopes and video recorders can be incorporated. In addition, single-image recording triggered by user-defined parameters is possible.
Unlike most tensile testers, this instrument has been designed for horizontal operation. The orientation was, in fact, dictated by the size of the samples being processed. “In a vertical setup, a fixation system weighing more than 2 N would exceed the measurement range of the force sensor,” says Use. “The horizontal alignment of our system results in a near-zero offset. This enables use of the force sensor’s complete measurement range.”
Samples measuring 4 Ą 8 mm and between 5 and 8 µm in thickness can be accommodated by the existing device. Other fixation systems are available for varying sample sizes. The modular hardware and software also can be easily adapted to facilitate various applications.
Modularity and flexibility are among the system’s key attributes, stresses Use. “It is not limited to performing tensile tests on human tissue. Minute samples of any elastic material, biological or otherwise, are prime candidates for this machine.”
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