Remotely Actuated Optothermal Robotic Microjoints Based on Spiral Bimaterial Design

In this article, we propose laser actuated microjoints which can be remotely actuated in both air and water. Their actuation relies on the optothermal response of a spiral bimaterial. The microjoints are fabricated using two-photon polymerization technology that offers the ability to tune the thermal and mechanical properties of the material by controlling the laser printing power. Modeling is first conducted to verify the parameters of the spiral that affect the rotational displacement and generated torque of the microjoint. Then, microjoints having a diameter of less than 200 \$\textbackslashmu\$m are characterized. The microjoints can realize a maximum deflection of approximately 8.5\$<\^>{\textbackslashcirc }\$, a force in the \$\textbackslashmu\$N-order using a 265-\$\textbackslashmu\$m long arm, an actuation repeatability of more than 100 times, and a time response of approximately 34 ms. Finally, the microjoints are implemented in a microgripper and an xy serial microarm. Successful micromanipulation of 40 \$\textbackslashmu\$m microbeads using the microgripper, and the simultaneous actuation of multiple microjoints of the xy serial microarm with two degrees of freedom are shown. This kind of rotational, compact, selective, and remotely actuated microjoints would allow the deployment of individually controlled mobile microrobots with several degrees of freedom for complex applications such as cell manipulation and microassembly.