Pneumatic microfinger with balloon fins for linear motion using 3D printed molds

• Development of unique balloon fin actuator designs, casted in polydimethylsiloxane (PDMS) polymer from 3D-printed molds.
• Design of vertical microballoon fins to produce a linear change in bend angle with the injection of pressurized air.
• Close agreement of deflection experiments with hyperelastic Ogden model.
• Experimental validation of static bending and mechanical force of various designs of balloon fin actuators.
• Improved reliability of balloon fin actuators by designing 3D actuators that reduce stress concentrations, which ultimately lead to device failure.
• Accomplishment of multi-directional object transfer tasks using grouped balloon fin actuators.

Polymer-based pneumatic balloon actuators consisting of novel trapezoidal vertical microballoon fins were fabricated by three-dimensional (3D) printed molds and validated experimentally. The introduction of 3D printed molds for pneumatic actuation provides additional freedom in the design of actuators, removing the limitation of extruded 2D shapes that is present with conventional microfabrication. Whereas conventional balloon actuators exhibit nonlinear response to applied pressure, the presence of balloon fins with 100 s-μm width was shown to produce a linear change in bend angle with the injection of pressurized air. The balloon fins also mitigate stress concentrations that can lead to material failure. Static bending (exceeding 80° bend angle) and the mechanical force of the fabricated microfingers were tested and compared with analytical models. The expanded design space permitted by 3D printing allows actuator designs to achieve a given deflection with less stress in the material as compared to planar designs. Feasibility of this design flexibility and fast prototyping enabled by the 3D printed molding process was demonstrated by fabricating and testing various designs of microfingers. When grouped, the microfingers with balloon fins can successfully accomplish complex object transfer tasks (i.e., multi-directional actuation with independently controlled displacement).