Foamin, which consists of a single wire connected to a piece of foam and a microcontroller, detects multiple deformations or touch inputs. (Image Credit: University of Tokyo)
Tactile sensors provide robots with enhanced movement or improved granularity capabilities. Soft sensors enable human-computer interfaces to have more interactivity. These sensors were difficult to utilize in the past because they needed multiple devices or complex wiring. To overcome that, researchers from the University of Tokyo and Mercari R4D developed Foamin, a touch-sensitive sensor with gesture detection capabilities. It identifies when it’s touched, held, pinched, grasped, and compressed by a human. The researchers say this soft sensor could have applications for a musical instrument, numeric keypad, and smart cushion.
Foamin is comprised of conductive foam, a surface-covering shield, and a single wire connected to the microcontroller. The foam’s surface contains a series of rows that are separated by air, serving as an insulator, which forms a capacitor. The conductive polyurethane foam was configured like an electric circuit. Gliding across the surface with a finger causes the circuit’s capacitor and resistor to change. The Arduino Uno measures this impedance, and once data filtering was complete, the team collected a set of 60 points per gesture. Afterward, they used this data to train a model and achieved 100% accuracy with an attached mesh shield compared to 81% without the mesh shield. Gestures were conducted ten times on Foamin.
The researchers implemented a shield mesh on the foam’s surface, improving accuracy readings. (Image Credit: University of Tokyo)
The team also developed a program to run the Swept-Frequency Capacitive Sensing. The AC voltage sweeps were at 184 different frequencies in the range of 35 kHz to 200 kHz. Swept frequencies were selected in the interval of 2 kHz to 5 kHz.
Additionally, Foamin can be used in deformable musical instruments, a soft numeric keypad, and a cushion. A musical instrument, which makes different sounds when a user holds, pinches, and grasps it, was implemented with Foamin. The team also implemented a numeric keypad, which has twelve buttons, that detects when a user presses it with their finger. A 250 mm x 250 mm x 100 mm pillow detects different sitting postures and can be used for health monitoring.
The researchers want to improve the wiring design for different applications. They also plan on exploring techniques to help identify and detect when Foamin is being twisted, sheared, and bent. Lastly, they plan on enhancing the mesh shield, allowing for a more clarified design space of the sensor.
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