Highly porous scaffold are needed in tissue engineering to allow cells to grow. Many schemes of producing scaffolds using biodegradable polymers have been developed. However, the majority of these fabrication techniques can be described by batch processes and organic solvents are used in most cases. Since organic solvents are in general harmful to cell, it has been desired to develop the non-organic solvent–based fabrication technique. Physical foaming techniques that use CO2 or N2 as blowing agents have been proposed as potential techniques to meet the requirements. But, the foaming techniques have either fallen short of scaffolds’ requirements on porosity and interconnectivity, failed to avoid using organic solvent completely or needed to combine other techniques such as salt leaching. In this study, acrylic-modified polytetrafluoroethylene (PTFE), Metablen A-3000 (acrylic-modified PTFE), was used for modifying the viscoelastic property of Poly lactic acid (PLA) resins. The modifier forms a fine well-dispersed fibril network in molten thermoplastic resin, which greatly improves the melt tension and the strain hardening behavior of PLA. Micro-cellular foam injection molding with coreback operation was employed to foam the PLA with nitrogen at a high expansion ratio, where fibrils of the Metablen A-3000 induced the crystal and bubble nucleation. As a result, highly porous and interconnected PLA matrices could be prepared without combing any other processing techniques. The porosity could be controlled by the biaxial deformation, which could be manipulated by core-back distance and rate. The inter-connectivity could be controlled by the elongational deformation, which could be manipulated mainly by core-back distance and holding time. By adjusting those processing conditions, hierarchical cell morphology comprised of micro-scale voids and nano-meter scale void with fibrils were obtained. Its open cell content became higher than 80% without skin layers.