Materials with a desired refraction coefficient can be made by embedding small particles

A method is proposed to create materials with a desired refraction coefficient, possibly negative one. The method consists of embedding into a given material small particles. Given $n_0(x)$, the refraction coefficient of the original material in a bounded domain $D \subset \R^3$, and a desired refraction coefficient $n(x)$, one calculates the number $N(x)$ of small particles, to be embedded in $D$ around a point $x \in D$ per unit volume of $D$, in order that the resulting new material has refraction coefficient $n(x)$.