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A reprogrammable microactuator system is presented, consisting of antagonistic shape memory alloy (SMA) microactuators for bidirectional folding of miniature-scale tiles following the concept of origami. Additional integrated heatable soft-magnetic pads with low ferromagnetic transition temperature allow for control of magnetic latching forces. The strongly coupled thermo-mechanical and thermo-magnetic properties of the microactuator and magnetic subsystems are taken into account in a model-based design to enable their selective control by Joule heating. A procedure for local shape setting of the SMA microactuators is presented to adjust their memory shape at either maximum or minimum bending angle and, thus, to functionalize their performance as protagonists or antagonists. A microfabrication process is developed that takes the specific requirements for processing the various materials and structures into account. A demonstrator system consisting of four triangular tiles with an edge length of 500 µm and an angular range of about ±100° is introduced that is programmed to adopt the shape of a pyramid and later on reprogrammed to self-unlatch, self-unfold, and subsequently to adopt the shape of a table.
Gottwald et al. (Thu,) studied this question.