Researchers from the University of Tokyo and Mercari R4D have created a novel soft, deformable foam sensor for multimodal touch inputs and gesture sensing. The conductive foam, known as Foamin, can detect deformable gestures, including touching, squeezing, compressing, and grasping via a single wire embedded within the foam. Its design is simple and comprises a soft conductive foam, a shield that covers the surface, and a single wire that connects to a microcontroller.
The foam is made from conductive polyurethane configured like an electric circuit, which completes when deformed, but can also recognize touch inputs by fingers and hands due to changes in impedance on the surface material. The mesh-patterned surface shield constrains the change in the contact area via SFCS (Swept-Frequency Capacitive Sensing), making it easier to differentiate between touches and deformation or position. An Arduino Uno is used to process the SFCS information, which uses AC voltage sweeps at 184 different frequencies ranging from 35 kHz to 200 kHz.
The application range for Foamin is extensive and includes deformable musical instruments that change their sound based on the deformation. A soft numeric keypad was also created with 12 buttons that utilize inputs by touch. The researchers built a cushion that can identify different postures while sitting. The researchers state that future revisions of the Foamin sensor would incorporate a more efficient wiring design tailored to specific applications and identify more complex deformation modes, such as twisting and bending. They are even looking into developing the mesh shield to increase the clarification of the design space for more accurate inputs.