A New Display Is Taking Shape

Shape displays, also known as deformable displays or shape-changing displays, are a fascinating class of emerging technologies that aim to go beyond traditional flat screens by enabling physical changes in their form and appearance. Unlike conventional displays that are static, shape displays offer the unique ability to transform their surfaces, creating dynamic 3D shapes and tangible textures. These displays can be constructed using various materials and mechanisms, such as shape-memory alloys, pneumatic actuators, or hydraulic pumps.

The potential applications of shape displays are vast and diverse. One prominent use case is in user interfaces, where these displays can enhance interaction and user experience. Imagine a smartphone with a shape display that provides tactile feedback for different functions, making buttons feel more distinct, or a gaming console with controllers that physically morph to match the in-game environment. Additionally, shape displays have significant implications in virtual reality and augmented reality applications, enabling users to feel and interact with virtual objects in a more realistic manner.

Despite the exciting possibilities, current shape display systems face some significant limitations that hinder their widespread adoption. One key challenge is the relatively low resolution of the displays. Creating intricate shapes or high-fidelity textures requires a high number of individual actuator units, which can be technically challenging and expensive to implement. Moreover, the refresh rates of shape displays tend to be slower than those of regular screens, resulting in visible delays when transforming shapes or updating textures. Many shape displays also rely on large external systems to drive actuation, which can be bulky and cumbersome, limiting the areas of practical application.

An innovative new shape display created by researchers at the University of Colorado Boulder overcomes many of the limitations of existing systems. This work could enable a new generation of high-fidelity shape displays with rapid refresh rates. The soft robotic display also has a mechanism to detect touches with a high degree of accuracy, and implements a control system that enables individual actuation of each pixel. And very importantly, this display does not require a large external system to drive it.

The researchers designed a 10 by 10 grid of Hydraulically Amplified Self-healing Electrostatic (HASEL) actuator cells. These soft electrohydraulic actuators are both powerful and capable of actuating at a high frequency. An elastic surface skin serves as a barrier between these cells and the outside environment. An interference-free magnetic-based sensor, embedded in the topmost layer, was leveraged to detect deformations of the surface skin to recognize touches with very high levels of precision.

The resulting display is relatively high resolution, at least in comparison to existing technologies. It has also been demonstrated to have a refresh rate of up to 50 Hz, which is exceedingly good for shape displays, and even rivals the speeds at which video is typically played back at. And the innovative touch sensing system eliminates the need for external camera-based systems that are commonly used in such devices. A unified control system was developed that could drive all of the pixels, which allowed an onboard microcontroller to drive the display, rather than an external computing system.

A number of experiments were conducted in which the display was shown to be capable of, for example, moving a ball around its surface in a programmed pattern. It could also display scrolling text and respond to touches from users with 0.1 mm sensitivity. In a more advanced demonstration, a banana was placed on one part of the display, while it calculated the weight and showed the value on another region of the screen. It was also shown that the rapid actuation could be leveraged to shake up and mix a vial of liquid.

While complex external systems are not necessary for operation, the researchers demonstrated that adding a camera can unlock additional functions. In one case, colored balls were placed on the surface of the display, and they were sorted, with each color being moved to its own corner.

Moving forward, the team would like to scale their methods to larger displays with a higher pixel density. They also hope to explore using their shape display in other high-degree-of-freedom soft robots like continuum manipulators and bioinspired systems.