Soft porous polymer materials, a new range of acoustic metasurfaces*

In 2011 a new range of 2D materials, widely known as metasurfaces, has emerged. These planar metamaterials of subwavelength thicknesses, capable of wave front shaping, consist of a single or several layers of artificial structure¹.

In general, metasurfaces are engineered by assembling arrays of deep sub wavelength building blocks. Here, we present a bottom-up approach which is based on soft-porous material: the dependence of the refractive index of soft porous polymer materials with their porosity enable us to fabricate acoustic gradient-index (GRIN) metasurfaces¹. Yet, their fabrication requires photo-polymerization of the thin film, which is made difficult by the presence of porogenic agents that scatter light. We will present a rational approach to understand the coupling between photo-chemistry and light scattering (in scattering media), and we will illustrate how the use of grayscale lithography facilitates the generation of this high precision microstructures.

(1) Jin, Y.; Kumar, R.; Poncelet, O.; Mondain-Monval, O.; Brunet, T. Flat Acoustics with Soft Gradient-Index Metasurfaces. Nat. Commun. 2019, 10 (1).