Fluid Driven Membrane Actuation for Reconfigurable Acoustic Manipulation.

Acoustic metamaterials based on out‐of‐plane actuation can flexibly reconfigure arrayed unit cells on demand, to shape sound fields for applications such as beam formation or holography. However, implementing active reconfiguration on the millimeter‐scale is challenging, due to the lack of suitable actuation methods. Besides electronic complexity, current methods suffer from limited actuation range (sub‐millimeter), and discrete steps inhibit smooth sound modulation. Here, a novel fluid‐driven approach for continuous out‐of‐plane actuation is presented. A three dimensionally (3D)‐printed fluidic chip is integrated with an elastomeric membrane, and selective inflation of membrane sections actuates acoustic reflector unit cells according to their shape and position. The compact device enables displacements >5 mm without coupling mechanisms or external power. It is experimentally demonstrate single‐channel and multi‐channel prototypes, including an ultrasonic metasurface built for controllable acoustic focusing at five different locations. The fluidic chips are monolithically printed via digital light processing without internal support material, and the membranes are fabricated by accessible and cost‐effective spacer‐based fabrication. The methods are reproducible and eliminate complex processes (e.g., adhesion of layers) commonly associated with multi‐layered micro/milli fluidic devices. The outlined approaches and concepts in this work can be applied beyond the field of metamaterials, such as for visual displays, or tactile devices. [ABSTRACT FROM AUTHOR]