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Suction cups are commonly used as adhering and grasping devices. This study proposes a methodology to expand the applicability of suction cups. A suction cup is developed with a soft pad which consists of stretchable electrodes and insulating layers that bond to the bottom of the main body of the suction cup. When the stretchable electrodes generate an electrostatic attraction between the electrodes and the object, the pad deforms, filling the gaps between the pad and the object. Due to the soft pad, the amount of incoming air is significantly reduced compared to a normal suction cup. Experiments reveal the effect of these features. Applying a high voltage to the stretchable electrodes increases the holding success ratio of the suction cup in the normal direction for smooth and rough surfaces due to the stretchable electrodes. Measuring the negative pressure inside the suction cup confirms that the electrostatic force maintains the adhesion force on both smooth and rough surfaces. Thus, the electrostatic force and stretchability of the soft pad greatly increase the adhesion force of the suction cup. Furthermore, the electrostatic force prevents a slip of the suction cup, which improves the performance of the suction cup.

Soft robots with dynamic motion could be used in a variety of applications involving the handling of fragile materials. Rotational motors are often used as actuators to provide functions for robots (e.g., vibration, locomotion, and suction). To broaden the applications of soft robots, it will be necessary to develop a rotational motor that does not prevent robots from undergoing deformation. In this study, we developed a deformable motor based on dielectric elastomer actuators (DEAs) that is lightweight, consumes little energy, and does not generate a magnetic field. We tested the new motor in two experiments. First, we showed that internal stress changes in the DEAs were transmitted to the mechanism that rotates the motor. Second, we demonstrated that the deformable motor rotated even when it was deformed by an external force. In particular, the rotational performance did not decrease when an external force was applied to deform the motor into an elliptical shape. Our motor opens the door to applications of rotational motion to soft robots.

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