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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] [ABSTRACT FROM AUTHOR]

The fabrication and integration of microactuators with 3D micromechanisms are necessary to develop microrobots with higher capability and complexity. In this work, a two-step fabrication method combining 3D printing with two-photon polymerization (TPP) and aluminum sputtering is demonstrated. Actuators using two different transduction mechanisms (thermal and electrostatic) were fabricated in this process, and a thermal actuator was printed with a mechanism in three-dimensional space without additional assembly steps. This work also provides parameterized characterizations which can be used as design guidelines for building actuators and mechanisms. A design approach to electrically isolate the actuators from the substrate is introduced so that the device can be functional after two fabrication steps without patterning the metal layer. Metal coverage on the sidewalls of trenches are characterized, which provides a design space for deciding electrode gaps and heights in electrostatic actuators. Using these guidelines, 500 $\mu \text{m}$ long thermal actuators showed a maximum displacement of 18.0 $\mu \text{m}$ at 8.31mW and reliably actuated up to 8,500 cycles. An interdigitated electrostatic comb-drive actuator was also successfully demonstrated, displacing 12.7 $\mu \text{m}$ when 160V was applied. Finally, a 3D actuated mechanism was designed by incorporating a thermal actuator with 3D compliant mechanisms to flap 250 $\mu \text{m}$ long wings. Flapping motion was successfully demonstrated. [2020-0010] [ABSTRACT FROM AUTHOR]

Creating 3D‐printed parts with embedded circuitry is the next frontier in additive manufacturing, but printing of conductors with performance comparable to bulk metals such as copper is a difficult challenge. A hybrid process based on 3D printing followed by electroplating on highly conductive thermoplastic filament is used to manufacture 3D circuit boards and electronic packaging. Dual extruder heads on a standard fused filament fabrication printer are used to selectively define regions for electroplating, allowing distinct traces and multiple materials to be patterned in the same 3D‐printed parts. Using this approach, a 3D‐printed surface‐mount package and a 555 timer oscillator circuit are demonstrated, including soldering of components onto the electroplated copper surface. [ABSTRACT FROM AUTHOR]