Design of a Microscale Optomechanical Load Cell for Micro-/Nanostructured Materials Testing Applications

The conceptual design of a microfabricated load cell for mechanical testing of materials is presented that utilizes radiation pressure for the application of load. Using a laser as the source of radiation pressure cyclic and quasi-static materials testing is possible in force, spatial and temporal ranges not previously accessible. The overall design consists of 3 subsystems working in unison for the testing of micro-/nanostructured materials in tension, compression, and bending. One subsystem applies radiation pressure (load); a second subsystem measures displacement optically; and the third subsystem is the optomechanical load cell (OMLC) itself with which the other two subsystems interact. The OMLC translates in one dimension and contains a thermal dissipation structure. A detailed design of the OMLC is presented that takes into consideration optical, mechanical, and thermal considerations when a 1 W laser at 532 nm is utilized. With analytical and computational models, force, displacement, and temporal resolutions are demonstrated. Specifically, it is shown that the design is capable of forces from fN to mN, with 10 pm of displacement resolution and cyclic loads of up to 1 MHz.