Hyunwoo Kim

Shape-morphing displays alter their surface geometry to convey information through three-dimensional shapes. However, rapid transformation into seamless shapes with multimodal tactile sensations poses challenges. Here, we introduce a versatile soft shape-morphing and tactile display, using a novel actuator that combines a PVC gel composite, dielectric liquid, and an electrode array. Proposed device facilitates on-demand liquid flow control through electrohydraulic actuation. Liquid channels within the device can be dynamically reconfigured using localized electrostatic zipping, enabling swift shape morphing and reconfiguration into diverse seamless 3D shapes. Our device achieves a large deformation and high output force, in a slim and lightweight framework. It also offers various haptic feedback, including dynamic tactile patterns and vibrations for localizable surface textures on the morphed shape. Additionally, its potential in robotics was demonstrated through high-speed object manipulation, leveraging liquid flow–induced inertia. In summary, our innovative soft shape-morphing tactile display could open new ways that we interact with technology, offering a more immersive and intuitive experience.

This letter presents a novel soft vibrotactile interface with a wide acceleration bandwidth that can be applied to a curved surface, such as a steering wheel. This haptic interface utilizes the surface charge-inducing characteristic of polyvinyl chloride (PVC) gel and adopts a design where hydraulic pressure is induced upon actuation. This working principle significantly increases the output force of the device, which enables a high-performance haptic interface. In addition, the small contact angle due to its curved shape was analyzed as an important parameter for high-frequency performance. Results showed that the proposed haptic interface can generate sufficient acceleration performance (>3 G) over a broad frequency range (90-700 Hz) with a maximum value near 6 G. Due to this high performance, user test participants could certainly feel the generated vibration with a sensation level of 22.5-44.8 dB from 10-360 Hz at 3 kV.

Herein, a novel soft actuator design is presented that simultaneously enables a high‐output force at a low operating voltage and an adjustable large normal displacement. The electrohydraulic actuator powered by induced interfacial charge (EPIC) uses the amplified electrostatic force when the surface charge‐inducing phenomenon of the polyvinyl chloride (PVC) gel and the geometrical gradient of the actuator are combined to reinforce the zipping motion of the liquid layer. This actuator produces a more than 50‐fold higher blocking force than conventional dielectric liquid‐coupled electrostatic actuators at 2 kV. This implies the possibility of expanding the applicability of soft actuators to high‐power transducers. This actuator is modeled as parallel capacitors by considering the interfacial‐induced charge; the ratio of the dielectric constant of the polymer film to that of the dielectric liquid is analyzed as the principal design criterion for optimizing the performance characteristics. The actuator prototype exerts a force as high as 16 times its body weight (25.5 g) and exhibits a large normal displacement of more than 20% of its height (8.5 mm). Furthermore, four actuators can lift a weight of 1.25 kg and one actuator can be used as a large‐aperture (diameter: 30 mm) varifocal lens (374% focal length variation).

This paper reviews state-of-the-art dielectric elastomer actuators (DEAs) and their future perspectives as soft actuators which have recently been considered as a key power generation component for soft robots. This paper begins with the introduction of the working principle of the dielectric elastomer actuators. Because the operation of DEA includes the physics of both mechanical viscoelastic properties and dielectric characteristics, we describe theoretical modeling methods for the DEA before introducing applications. In addition, the design of artificial muscles based on DEA is also introduced. This paper reviews four popular subjects for the application of DEA: soft robot hand, locomotion robots, wearable devices, and tunable optical components. Other potential applications and challenging issues are described in the conclusion.