Acoustic metamaterials are artificial structures, often lattice of resonators, with unusual properties. They can be engineered to stop wave propagation in specific frequency bands. Once manufactured, their dispersive qualities remain invariant in time and space, limiting their practical use. Actively tuned arrangements have received growing interest to address this issue. Here, we introduce a new class of active metamaterial made from dual-state unit cells, either vibration sources when powered or passive resonators when left disconnected. They possess self-tuning capabilities, enabling deep subwavelength band gaps to automatically match the carrier signal of powered cells, typically around 200Hz. Swift electronic commutations between both states establish the basis for real-time reconfiguration of waveguides and shaping of vibration patterns. A series of experiments highlight how these tailored acceleration fields can spatially encode information relevant to human touch. This novel metamaterial can readily be made using off-the-shelf smartphone vibration motors, paving the way for a widespread adoption of multi-touch tactile displays.

翻译：声学超材料是一种人工结构，通常由谐振器阵列构成，具有非常规物理特性。通过设计可使其在特定频段内阻止波传播。传统超材料一旦制备完成，其色散特性在时空维度上保持恒定，这限制了实际应用。为解决此问题，主动调谐结构日益受到关注。本文提出一种新型主动超材料，其由双态晶胞构成：通电时作为振动源，断开时则充当被动谐振器。该材料具备自调谐能力，可使深亚波长带隙自动匹配通电晶胞的载波信号（典型频率约200Hz）。通过两种状态间的快速电子切换，实现了波导结构的实时重构与振动模式调控。系列实验表明，这种定制化加速度场可在空间维度编码与人类触觉相关的信息。该新型超材料可直接采用商用智能手机振动电机制备，为推广多触点触觉显示技术开辟了新途径。