Morphological and Elemental Characterization of Thermoformed Piezoelectret Films with Variable Channel Geometries

This study presents the morphological and elemental characterization of the tubular structure of thermoformed piezoelectrets with open voids. The thermoformed structures were analyzed without applying the metallized layers required for electrical charging and piezoelectric measurements. Four samples were investigated: two single-layer thermoformed piezoelectret (SLTP) samples with channel widths of 2 mm and 3 mm, and two thermoformed magneto-piezoelectret (TMP) samples with geometries corresponding to those of the SLTP samples. The samples were prepared by pressure thermoforming (250 ∘C for 15 s) of fluorinated ethylene propylene (FEP) films using polytetrafluoroethylene (PTFE) templates. In the TMP samples, a self-adhesive magnetic layer (300 μm thick) was incorporated before the final sealing step by applying an additional layer of FEP on top of the layered assembly. Cross-sectional scanning electron microscopy (SEM) revealed the regular formation of tubular channels, the integrity of the interfaces, and the slight dimensional variations associated with the channel geometry. Energy-dispersive X-ray spectroscopy (EDS) confirmed elemental signatures consistent with FEP and magnetic layer inclusions, with no evidence of external contamination. The results demonstrated the morphological and compositional stability of the structures produced and indicated that wider geometries may require adjustments to the thermoforming parameters to optimize the interlayer cohesion. The results provide relevant structural and compositional parameters for improving the design and quality control of thermoformed piezoelectrets with and without magnetic components. SEM–EDS reveals structural stability of thermoformed FEP channels Channel width influences geometric distortion and interfacial cohesion Magnetic layer increases structural heterogeneity in TMP devices Normalized EDS confirms compositional integrity of SLTP and TMP Wider channels require thermoforming parameter optimization SEM–EDS reveals structural stability of thermoformed FEP channels Channel width influences geometric distortion and interfacial cohesion Magnetic layer increases structural heterogeneity in TMP devices Normalized EDS confirms compositional integrity of SLTP and TMP Wider channels require thermoforming parameter optimization