Fig. 1: Overview of the dual-state active acoustic metamaterial.
From: Dynamic shaping of multi-touch stimuli by programmable acoustic metamaterial
a Schematic of a 2D tactile display made from a square tessellation of dual-state unit cells. Cells in a resonator state (blank) form a metamaterial, insulating cells in an actuator state (colored). The resulting vibration patterns can be reconfigured in real time. A reduced linear array of 11 unit cells is outlined in black. b Equivalent electromechanical model in both states: the “actuator state” and the “resonator state''. Mechanical and electrical energy fluxes are overlaid (dissipative effects are discarded). The electrical circuit consists of a resistance Ra, an electromotive force ea, and an inductance La. The mechanical system includes a moving mass m and a spring K. c Schematic of the linear array of 11 unit cells made with LRAs. d Exploded view of an off-the-shelf LRA with, from top to bottom, a FR-4 substrate (SU), a voice coil (CL), a flexure spring (FL), a moving mass with a neodymium magnet (MM), and a steel casing (SC). e Impulse response of a single LRA measured using a laser interferometer. Both the gain and phase, averaged over 50 trials, are well approximated by a second-order model with minimal damping. f Top view of the prototype with embedded electronics.
