Dynamically Reconfigurable Shape-Morphing and Tactile Display Via Hydraulically Coupled Mergeable and Splittable PVC Gel Actuator

Shape-morphing displays that modulate their surface geometry to encode information via three-dimensional configurations have significant interdisciplinary applications. Recent advancements have shifted to soft materials that morph into continuous three-dimensional shapes through various types of stimuli-responsive actuation [1,2]. However, these strategies have limitations such as low speed for shape morphing, and absence of multi-modality to provide tactile sensations with surface geometry. Meanwhile, electrohydraulic actuation has addressed key challenges with high-speed response and significant deformation potential [3,4]. However, the rapid transition into seamless and complex 3D shapes that afford multimodal tactile feedback still presents a considerable technical challenge.<br/>Addressing this, our research introduces a novel soft shape-morphing and tactile display that utilizes an innovative actuator consisting of a polyvinyl chloride (PVC) gel composite, a dielectric liquid, and an electrode matrix to create programmable pressure patterns. This mechanism enables on-demand manipulation of liquid flow via electrohydraulic actuation, facilitating unimpeded internal fluid dynamics. We designed a multi-layered functional polymer composed of PVC gels and an MWCNT electrode, which acts as an active interface, facilitating electrohydraulic actuation while simultaneously enabling the formation of 3D geometries. Thanks to the charge accumulation properties of the PVC gel, the interface has relatively low actuation voltage compared to conventional dielectric elastomers [4]. We analyzed the mechanical and dielectric properties by varying weight fraction of plasticizer of PVC gel, ultimately determining the optimal ratio by considering high dielectric constant and low hysteresis.<br/>Moreover, the design allows dynamic alteration of liquid channels through localized electrostatic activation of specific areas, resulting in rapid shape morphing (45 ms) and transitions into various seamless 3D configurations while generating a large deformation up to 2.5 mm and an exertion force of 2.0 N, despite its slim (1.5 mm) and lightweight (7 g) structure. This capability provides various haptic feedback modalities, including dynamic tactile patterns and vibrations generating distinguishable surface textures on morphed geometries that are verified through empirical user evaluations. Additionally, the developed shape-morphing display allows dynamic motions of object through morphing surface by leveraging liquid flow-induced inertia. In essence, our soft shape-morphing and tactile display introduces novel interaction paradigms with technology, promoting more immersive and intuitive user experiences.<br/><br/>This work was supported by the National Research Council of Science & Technology (NST) grant by the Korea government (MSIT) (CRC23021-000), Samsung Science and Technology Foundation under Project Number SRFC-IT2102-04, and the internal grant of Electronics and Telecommunications Research Institute (ETRI) (24YB1700, Development of light driven three-dimensional morphing technology for tangible visuo-haptic interaction).<br/><br/>[1] Rasmussen, M. K., et al. & Hornbæk, K. Shape-changing interfaces: a review of the design space and open research questions. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems 735-744 (2012).<br/>[2] Qu, X., et al. Refreshable braille display system based on triboelectric nanogenerator and dielectric elastomer. Adv. Funct. Mater. 31, 2006612 (2021).<br/>[3] Shultz, C., et al. Flat panel haptics: Embedded electroosmotic pumps for scalable shape displays. In Proceedings of the 2023 CHI Conference on Human Factors in Computing Systems 1-16 (2023)<br/>[4] Kim, H., et al. High-output force electrohydraulic actuator powered by induced interfacial charges. Adv. Intell. Syst. 3, 2100006 (2021)