Hierarchical Integration of Thin-Film NiTi Actuators Using Additive Manufacturing for Microrobotics

Shape memory alloy (SMA) actuators can provide significant advantages for small-scale robotics given their robustness, energy density, and low voltage actuation. However, NiTi thin films typically found in SMA microactuators do not often provide useful forces and displacements for microrobotic applications. This work presents a fabrication process in which NiTi thin film actuators are integrated with two-photon polymerization (TPP) 3D printing to scale these actuators up for use in mesoscale systems. Individual unimorph actuators are characterized with respect to uniformity across many actuators so that actuators can be arrayed together for even larger forces or combined toward the operation of complex mechanisms. The resulting actuators are fast to prototype, reliable and stable (up to 5000 cycles), and can utilize complex geometries that are otherwise challenging to achieve with conventional MEMS microfabrication techniques. A 2D positioner is demonstrated by combining six individually controlled actuators with conventional mm-scale fabrication techniques (3D stereolithography printing, wire bonding and PCB assembly). The actuators are controlled by a commercial microcontroller and powered using a standard Lithium polymer battery. [2020-0208].