Pressure/strain piezoresistive are described that include a poled piezoelectric polymer such as PVDF or P(VDF-TrFE) and graphene. The poled piezoelectric polymer and the graphene are electronically coupled to form a heterojunction and provide an ultra-high sensitivity pressure/strain sensor. The sensors can be carried on a flexible supporting substrate such as PDMS or PET to exhibit high flexibility. The materials of formation can be biocompatible and the sensors can be wearable or implantable.