Researchers have developed a new method to 3D print mechanisms that detect how force is being applied to an object. The structures are made from a single piece of material, so they can be rapidly prototyped. A designer could use this method to 3D print interactive input devices, like a joystick, switch, or handheld controller, in one pass.
To accomplish this, the researchers integrated electrodes into structures made from metamaterials, which are materials divided into a grid of repeating cells. They also created editing software that helps users build these interactive devices.
Sensing can be integrated directly into the material structure of objects, enabling intelligent environments in which objects can sense each interaction with them. For instance, a chair or couch made from the smart material could detect the user’s body when the user sits on it and either use it to query particular functions (such as turning on the light or TV) or collect data for later analysis (such as detecting and correcting body posture).
Because metamaterials are made from a grid of cells, when the user applies force to a metamaterial object, some of the flexible, interior cells stretch or compress. The researchers took advantage of this by creating “conductive shear cells” — flexible cells that have two opposing walls made from conductive filament and two walls made from nonconductive filament. The conductive walls function as electrodes.
When a user applies force to the meta-material mechanism — moving a joystick handle or pressing the buttons on a controller — the conductive shear cells stretch or compress and the distance and overlapping area between the opposing electrodes changes. Using capacitive sensing, those changes can be measured and used to calculate the magnitude and direction of the applied forces, as well as rotation and acceleration. By understanding how joystick users apply forces, a designer could prototype unique handle shapes and sizes for people with limited grip strength in certain directions.
A designer could quickly create and tweak unique, flexible input devices for a computer, like a squeezable volume controller or bendable stylus. Meta-Sense, the 3D editor the researchers developed, enables this rapid prototyping. Users can manually integrate sensing into a metamaterial design or let the software automatically place the conductive shear cells in optimal locations.
The tool simulates how the object will be deformed when different forces are applied and then uses this simulated deformation to calculate which cells have the maximum distance change. The cells that change the most are the optimal candidates to be conductive shear cells.