Abstract: PHA-based microporous and tough articles having node and fibril structures, and processes to create these articles using a below the melt processing approach are provided. A method of forming a porous expanded PHA composite comprising a porous PHA material may include depositing a partially crystallized polyhydroxyalkanoate (PHA) polymer on a substrate at a deposition temperature below a melting temperature of the PHA polymer to form a PHA-substrate composite, and expanding the PHA-substrate composite at a temperature between the glass transition temperature of the PHA polymer and the melting temperature of the PHA polymer.