The LEGO of Haptic Interfaces

If we are ever going to really be fully immersed in a virtual experience, it is going to take a lot more than just realistic visuals. No matter how impressive the graphics capabilities of a virtual reality (VR) headset are, the experience is going to fall flat the moment one reaches for a digital object and feels nothing. To bridge this gap between the real and virtual worlds, a large number of haptic user interfaces have been introduced in recent years. These interfaces seek to artificially stimulate the sense of touch in a realistic manner.

It can be hard to get a handle on which haptic device is the best for a particular application because there are an awful lot of different options out there. This is due to the fact that most systems are designed for specific use cases, so the form that they take, and the types of sensations that they can produce, are tailored to that experience. Nobody really wants to switch to a different interface for each application, or have to buy a dozen different devices, so a team led by researchers at the Swiss Federal Technology Institute of Lausanne designed a reconfigurable haptic interface that can adapt to different situations.

Called Digits, their solution is made up of modules that can be linked together to form more complex structures. Each rigid module is connected to others via flexible joints, something like the links in a chain. The joints contain pouches of air that can be either inflated or deflated by a pneumatic pump to control shape and stiffness, and to provide haptic feedback.

With many different configurations available, Digits can shift form and function based on the user’s needs. Of those possible configurations, the researchers demonstrated two options: the wearable TangiGlove and the handheld TangiBall. As the names imply, one takes the form of a wearable glove, and the other, a ball. These demonstrations show how a single modular system can be flexibly adapted for applications ranging from virtual reality to motor rehabilitation therapy by simply clicking the modules together in different ways.

Unlike the many haptic devices that are confined to one style of interaction, Digits can operate in both open-chain and closed-chain configurations. An open-chain configuration, such as the TangiGlove, connects modules in a series like a robotic exoskeleton and is ideal for providing resistance or force feedback along joints. The TangiBall, on the other hand, employs a closed-chain configuration in which the modules form loops, allowing the system to shift shape dramatically while delivering multi-directional tactile feedback.

For control of the interface, the researchers extended an open source software platform called Feelix to allow users to intuitively create haptic feedback profiles. This software leverages machine learning to interpret data from embedded pressure sensors, enabling real-time adjustment and interaction recognition.

Ultimately, the goal of the project is to offer a universal haptic framework that can scale across applications while adapting to user needs. Whether the use case is a VR game, a remote robotic operation, or a physical therapy session, the researchers' plan is to make Digits the right tool for every job.