Structural, Electrical and Electromechanical Properties Control Over Primary and Secondary Nucleation in Poly (L‐Lactic Acid) Film

ABSTRACT

In this work, we have studied the effects of thermal and electrical processing on crystallization, electrical, and electromechanical behavior of polymeric Poly (L‐lactic acid) (PLLA) films deposited on top of medical‐grade 316L stainless steel using the rapid thermal annealing (RTA) method. Stepwise annealing at 180°C and 120°C produced well‐defined crystalline spherulitic structures under an air atmosphere, while a vacuum atmosphere produced amorphous films, confirming the key role of nitrogen and oxygen elements in the promotion of the primary nucleation process. The secondary nucleation process was further modulated by corona‐poling discharge at a DC bias voltage of –5 kV, which induced dipole alignment as evidenced by Maltese cross patterns and enhanced birefringence. To achieve nanoscale control, Atomic Force Microscopy‐based local poling with electric fields of 3 GV/m was used to generate predefined polarization patterns. Kelvin Probe Force Microscopy and Piezoresponse Force Microscopy analyses confirmed reversible dipole switching, while Electrostatic Force Microscopy measurements revealed stable surface charges confined to crystalline regions, indicating that the observed charges are electromechanical and not electrostatic in origin. These results demonstrate a multiscale strategy for controlling crystallization and polarization in thin PLLA films. The combined RTA and electric‐field‐assisted methods enable precise tuning of piezoelectric properties in semicrystalline regions of PLLA for advanced sensing and bioelectronic applications.