Electroadhesive Auxetics as Programmable Layer Jamming Skins for Formable Crust Shape Displays (2211.05375v2)

Abstract: Shape displays are a class of haptic devices that enable whole-hand haptic exploration of 3D surfaces. However, their scalability is limited by the mechanical complexity and high cost of traditional actuator arrays. In this paper, we propose using electroadhesive auxetic skins as a strain-limiting layer to create programmable shape change in a continuous ("formable crust") shape display. Auxetic skins are manufactured as flexible printed circuit boards with dielectric-laminated electrodes on each auxetic unit cell (AUC), using monolithic fabrication to lower cost and assembly time. By layering multiple sheets and applying a voltage between electrodes on subsequent layers, electroadhesion locks individual AUCs, achieving a maximum in-plane stiffness variation of 7.6x with a power consumption of 50 uW/AUC. We first characterize an individual AUC and compare results to a kinematic model. We then validate the ability of a 5x5 AUC array to actively modify its own axial and transverse stiffness. Finally, we demonstrate this array in a continuous shape display as a strain-limiting skin to programmatically modulate the shape output of an inflatable LDPE pouch. Integrating electroadhesion with auxetics enables new capabilities for scalable, low-profile, and low-power control of flexible robotic systems.

• The paper introduces electroadhesive auxetic skins on flexible PCBs that use voltage to control stiffness, enabling the creation of scalable, low-power shape displays.
• This technology offers a scalable, low-profile, and energy-efficient alternative to traditional shape displays, with potential use in robotics and haptics.
• This work offers a foundation for developing metamaterials with programmable properties and has potential for advanced robotic surfaces and haptic systems.

Electroadhesive Auxetics as Programmable Layer Jamming Skins for Formable Crust Shape Displays

The research paper presents a novel approach to addressing the mechanical complexity and cost challenges faced by conventional shape displays using linear actuator arrays. The authors propose the utilization of electroadhesive auxetic skins as strain-limiting layers within continuous shape displays, referred to as "formable crusts." This innovative method leverages the properties of auxetics, which possess a negative Poisson's ratio, enabling effective conformation to various surface curvatures.

The central contribution of the paper is the development of auxetic skins as flexible printed circuit boards (PCBs), which are composed of dielectric-laminated electrodes on auxetic unit cells (AUCs). By applying a voltage across layers, electroadhesion is achieved, which increases in-plane stiffness by a factor of up to 7.6, while maintaining a power consumption as low as 50 µW per AUC. This work overcomes the traditional trade-offs between stiffness and flexibility, enabling the construction of shape displays that are more scalable, lower in profile, and consume less power, thus opening new avenues for flexible robotic systems.

The methodology embraced by the authors includes a combination of experimental validation with a model-based analysis. They present a detailed kinematic model for an individual electroadhesive auxetic layer, which correlates well with the empirical data. Subsequently, this model is extended to a 5x5 AUC array to reveal the global stiffness modulation capabilities of the material. This array is then deployed as a shape display skin over an inflatable low-density polyethylene (LDPE) pouch, demonstrating significant potential for responsive surface manipulation.

The results underscore a substantial improvement in stiffness control, with a notable variation in axial stiffness and transverse flexibility, showcasing the feasibility of these programmable skins in transforming the functionality of soft robotics and haptic feedback systems. With its low manufacturing cost and reduced energy demands, this technology promises to lower the barriers traditionally faced by developers of scalable tactile and haptic display systems.

The work has several promising implications. Theoretically, this method introduces a robust framework for further development of metamaterials with programmable mechanical properties. Practically, the research has potential applications in various domains such as virtual reality interfaces, adaptive grippers, and wearable robotics, which require precise stiffness control. The exploitation of electroadhesion in auxetic designs might catalyze future explorations into more advanced robotic surfaces capable of dynamic and responsive shape modulation.

However, challenges remain regarding the 3D modeling of these complex interactions, the enhancement of strain compatibility, and the integration with existing robotic systems for diversified applications. Future research directions could focus on refining the kinematic models to incorporate non-linear deformations and fatigue, optimizing auxetic designs for higher strains, and expanding the applicability of these materials to other domains requiring nuanced control of shape and texture.

In summary, the paper offers compelling insights into the viable integration of electroadhesion with auxetic designs, advancing our understanding of programmable materials and their potential utility in scalable and energy-efficient robotic systems.