How WEFT Works

Phenomenon

WEFT is using electrovibration to generate the feelings you’re perceiving. Electrovibration manifests as a variation in shear friction force - programmable sticking or sliding along the surface of an electrode.

The Disney Research papers have some good graphics to show the effect. In particular, showing the shear action of the effect, altering how your finger moves along a surface but not how that finger feels when stationary:

paper-shear-force paper-electrovibration-and-rev

Some key factors differentiate electrovibration and other haptic actuation technologies like piezo-disks or vibrating motors:

  • Silence—because the only moving part in the system is your finger, there’s no sound for others to overhear
  • Motion—because the electrovibration effect affects the “stickiness” of the finger and electrode, the pad or the finger must be moving for the effect to be perceivable. In my experience, finger motion is easier to work with (rather than pad motion) because human finger proprioception is much higher-resolution than our ability to judge the exaction motion of nearby objects.
  • Learnable—because this is a relatively new way to artificially receive sensory input, your brain will get better and better at resolving the signals; you’ll get better and better (up to a point) at telling the textures apart.

Circuit

Creating an electrovibration effect involves three steps:

  • Generate a current-limited high voltage source
  • Charge a dielectric-coated conductive pad with this voltage source
  • Modulate a path to ground for the charge on the above plate

paper-system-diagram