Phononic Crystals Applied to Localised Surface Haptics.

Metamaterials are solid lattices with periodicitiescommensurate with desired wavelengths. Their geometric fea-tures can endow the bulk material with unusual properties suchas, inter alia, negative indices of refraction or unique absorbingqualities. Mesoscale metamaterials can be designed to causethe occurence of phononic crystals in the ultrasonic domain.These localised phenomena induce fixed boundary conditionsthat correspond to acoustic mirrors which, in turn, can be usedto establish waveguides in thin plates. Ultrasonic lubricationhas been successfully applied to create haptic interfaces thatoperate by modulating the apparent friction of a surface. In thisstudy we demonstrate that phononic crystals can be designedto localise the modulation of friction in specific portions of thesurface of a thin plate, opening novel possibilities for the designof surface haptic interfaces.