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A cost-effective microindentation system for soft material characterization

Microindentation is a useful experimental technique for characterizing mechanical properties of soft materials for research in biomechanics, biomaterials, tissue engineering. Despite its powerful capabilities, the access to microindentation techniques is hampered by the low performance-to-cost ratio of current commercial microindentation systems. This paper describes a new approach for constructing microindentation systems from readily available laboratory resources, and reports a force-controlled, cost-effective microindentation system capable of elastic and viscoelastic characterization of soft materials. A micro-electro-mechanical systems (MEMS) based piezoresistive force sensor and a motorized micromanipulator are employed to indent a sample and collect the force-deformation data for extraction of elastic and viscoelastic parameters. To overcome the shortcomings of previously reported customized systems, closed-loop position and force controllers are designed and implemented to accurately regulate the indentation depth and force. Tests on elastomeric and hydrogel materials prove the effectiveness of the system for elastic, relaxation, and creep tests, providing comparable measurement results with commercial microindentation systems at a much lower cost.