The present invention relates to piezoresistive devices and pressure sensors incorporating such devices. At its most general, the invention provides a piezoresistive device, comprising a piezoresistive material positioned between an upper conductive layer and a lower conductive layer, wherein the piezoresistive material comprises carbon nanoparticles (most preferably graphene nanoplatelets, graphene or carbon nanotubes) dispersed in a polymer matrix material. The invention also relates to methods of manufacturing and using such devices.