A 3D-printed portable microindenter for mechanical characterization of soft materials

In this paper, we report a 3D-printed portable microindenter for measuring the mechanical properties of soft materials. The system is composed of three major components: (i) a Z-axis stage, (ii) a force-sensing indentation probe, and (iii) a data acquisition and control system. We construct most of the system parts (including the force sensing probe) by 3D printing, and perform mechanical design and analysis to guarantee the mechanical robustness of the system. The system is capable of performing high-precision, non-destructive material indentation testing with displacement and force sensing resolutions as low as 0.625 μm and 73 μN, respectively. The force-deformation data obtained during indentation are used to determine the mechanical characteristics of a soft material sample based on a Hertz's mechanical model. We also integrate several user-friendly features into the system, including a touch screen and customized software for convenient user-machine interactions. Using the microindenter, we perform elastic testing of polydimethylsiloxane (PDMS) with three base/curing agent ratios (w/w), and achieve consistent results of the materials' Young's moduli in good agreement with the previous results reported in the literature. This proves that our 3D-printed microindenter, although being custom-made and low-cost, maintains the accuracy and repeatability required for soft material testing.