Research Outcomes

Summary:

Improving the sensitivity of piezoelectric polymers including poly-L-lactic acid (PLLA) remains a critical challenge for practical applications. Gap electrospinning has been shown to enhance PVDF’s piezoelectric response, but whether this method is effective for PLLA remains unclear. In this study, gap electrospinning was utilized and the impact of hole geometries including shape (circular, square, and rectangular) and size (side length, aspect ratio, area) on fiber structure and piezoelectric properties was investigated, with PVDF as a reference. As expected, PVDF exhibited enhanced sensitivity with improved alignment. However, aligned PLLA fibers unexpectedly showed lower piezoelectric sensitivity compared to randomly oriented ones. Structural analysis revealed that although β-phase content in PLLA increased with fiber alignment, the highly disordered β-phase led to decreased crystallinity and weakened piezoelectric responses. Moreover, a strong linear relationship was observed between piezoelectric sensitivity and α/β-phase ratio rather than β-phase content in PLLA (Pearson coefficient of 0.994 and 0.993 for 12 and 18 wt.%, respectively). Although the measured piezoelectric sensitivity of PLLA fibers (e.g., 1.6 mV/N for 12 wt.% PLLA) was lower than reported polymer/inorganic or polymer/metal composite systems, finger-tapping tests and constant force pressing tests (0.98 N) both confirmed substantial output signals, with an average voltammetric response of -966 and -1008 mV, respectively. Furthermore, long-term durability was demonstrated through finger-tapping tests over 100 cycles and pressing tests over one week, showing good signal stability with degradation rates of less than 10%. These results underscore the potential of electrospun PLLA nanofibers as promising candidates for lightweight, flexible, and durable piezoelectric sensors in wearable electronics.

https://doi.org/10.1016/j.polymertesting.2025.108958