Parallel-beams magnetic actuator for in-situ transmission electron microscope observation of mechanical testing

Abstract

Abstract Understanding the microscopic mechanisms behind mechanical fractures is essential for enhancing material properties and increasing reliability through fatigue suppression. Conventional mechanical testing methods, such as indentation tests that press a sharp needle into a specimen or tensile tests using hydraulic pumps, are unable to capture nanoscale deformations under applied forces. As a result, the microscopic mechanisms that influence mechanical properties are often inferred indirectly, and material design largely depends on the engineer’s intuition and occasional serendipity. To overcome these challenges, in-situ observation techniques utilizing transmission electron microscopes (TEMs) have been developed to enable the observation of sample deformations at the nanoscale. However, despite their high resolution, conventional TEMs are limited by a small available space -often just a few millimeters- that restricts the application of sufficient force to fracture specimens. Traditional actuation methods, such as thermal expansion, electrostatic force, and piezoelectric actuators, fail to generate significant forces within such confined spaces. In response to these limitations, our research involved the development of a micromachine with multiple parallel beams. This device leverages the Laplace force generated by an electric current passing through the beams and the magnetic field of the TEM. We demonstrated the capability to produce significant force using the magnetic field from the microscope’s magnetic lens. The actuator developed in our study successfully generated forces exceeding 50 µN, marking a significant advancement in the in-situ observation capabilities for mechanical testing.