4D Printing of Soft Robotic Facial Muscles

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Cai, Jiyu
Vanhorn, Austin
Mullikin, Casey
Stabach, Jennifer
Alderman, Zach
Zhou, Wenchao

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University of Texas at Austin


4D printing is an emerging technology that prints 3D structures with smart materials that can respond to external stimuli and change shape over time. 4D printing represents a major manufacturing paradigm shift from single-function static structures to dynamic structures with highly integrated functionalities. Direct printing of dynamic structures can provide great benefits (e.g., design freedom, reduced weight, volume, and cost) to a wide variety of applications, such as sensors and actuators, and robotics. Soft robotics is a new direction of robotics in which hard and rigid components are replaced by soft and flexible materials to mimic actuation mechanisms in life, which are crucial for dealing with uncertain and dynamic tasks or environments. However, little research on direct printing of soft robotics has been reported. This paper presents a study on 4D printing of soft robotic facial muscles. Due to the short history of 4D printing, only a few smart materials have been successfully 4D printed, such as shape memory and thermo-responsive polymers, which have relatively small strains (~8%). In order to produce the large motion needed for facial muscles, dielectric elastomer actuators (DEAs), operating like a capacitor with a sheet of elastomer sandwiched by two compliant electrodes and known as artificial muscle for its high elastic energy density and capability of producing large strains (~200%) compared to other smart materials, is chosen as the actuator for our robotic facial muscles. In this paper, we report the first fully 4D printed soft robotic face using DEAs. A literature review on DEAs is first presented. In order to select the right material for our soft robotic face, the performance of different silicone-based candidate materials is tested and compared. A soft robotic face is then designed and fabricated using the selected material to achieve facial emotions by the motion of its lip and pupils actuated by the DEAs. This study demonstrates a 4D printed soft robotic face for the first time and the potential of 4D printing of soft robotics.


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