Mechanically soft neural implants When implanting a material into the body, not only does it need the right functional properties, but it also needs to have mechanical properties that match the native tissue or organ. If the material is too soft, it will be mechanically degraded, and if it is too hard it may get covered with scar tissue or it may damage the surrounding tissues. Starting with a transparent silicone substrate, Minev et al. patterned microfluidic channels to allow for drug delivery, and soft platinum/silicone electrodes and stretchable gold interconnects for transmitting electrical excitations and transferring electrophysiological signals. In tests of spinal cord implants, the soft neural implants showed biointegration and functionality within the central nervous system. Science , this issue p. 159