An in-situ, micro-mechanical setup with accurate, tri-axial, piezoelectric force sensing and positioning

To facilitate the accurate characterization of the mechanical behavior of micro-scale materials used in, e.g., microelectronics, experiments are required that mimic the actual loading conditions to which the material systems are subjected during fabrication and operation. Equally important is the recording of mechanical data in the form of multi-axial force measurements, and the measurement of kinematics by in-situ microscopic techniques. To this end, a relatively inexpensive, micro-mechanical testing rig is realized from commercially available piezoelectric actuators. It is shown that the setup measures forces with a resolution of ∼ 0.3 [mN] in the x- and y-directions, and ∼ 50 mN in the z-direction, over a range of 10 [N], yielding a high dynamic range in these directions,. Furthermore, displacements can be imposed with a resolution of ∼ 1 [nm] over a range of 200 [µm], in all three directions (x, y, z). The setup is compact, vacuum compatible, and specimens are loaded on top of the setup so that the viewing perspective is unobstructed, allowing for in-situ optical and scanning electron microscopy testing. A generic method is developed for measuring quasi-static forces by piezoelectric actuators. Furthermore, the challenges imposed by the use of commercial actuators, of which the technical specification are not fully known to the user, are overcome and the solution strategy is described. Proof-of-concept experiments on flexible, organic, light-emitting diodes demonstrate the potential of the setup to provide rich micro-mechanical data in the form of tri-axial force and displacement measurements. The commercial availability of the piezoelectric actuators, combined with the solutions to the associated problems constitute a generally accessible micro-mechanical test setup to investigate small-scale specimens under realistic loading conditions.