  We explore the range over which the elasticity of disordered spring networks
can be manipulated by the removal of selected bonds. By taking into account the
local response of a bond, we demonstrate that the effectiveness of pruning can
be improved so that auxetic (i.e., negative Poisson's ratio) materials can be
designed without the formation of cracks even while maintaining the global
isotropy of the network. The bulk, $B$, and shear, $G$, moduli scale with the
number of bonds removed and we estimate the exponents characterizing these
power laws. We also find that there are spatial correlation lengths in the
change of $B$ and $G$ upon removing different bonds that diverge as the network
approaches the isostatic limit where the excess coordination number $\Delta
Z\rightarrow0$.

Soft Condensed Matter