Poling-Free Hydroxyapatite/Polylactide Nanogenerator with Improved Piezoelectricity for Energy Harvesting

Abstract

Polylactide-based piezoelectric nanogenerators were designed and fabricated with improved piezoelectric performances by blending polylactide with hydroxyapatite. The addition of hydroxyapatite significantly improves the crystallinity of polylactide and helps to form hydrogen bonds, which further improved the piezoelectric output performance of these piezoelectric nanogenerators with over three times the open circuit voltage compared with that of pure-polylactide-based devices. Such excellent piezoelectricity of hydroxyapatite/polylactide-based nanogenerators give them great potential for energy harvesting fields.

Filler‐Enhanced Piezoelectricity of Poly‐L‐Lactide and Its Use as a Functional Ultrasound‐Activated Biomaterial

“…The surface of unidirectional high aspect ratio filler particles was able to interact with PLLA molecular chains consequently initiating oriented crystallization of highly ordered β PLLA phase. We were not able to detect hydrogen bonding between PLLA and HAp which was previously suspected to be the reason for HAp‐induced β PLLA phase formation, [ 29 ] therefore we assume that electrostatic interactions between cations (Ca 2+ or Ba 2+ ) along uniaxially oriented HAp or BT surface with CO groups in PLLA chains initiate forming more ordered β structure. The assumption is mainly made based on the changes of CO group stretching vibrations observed only in case of PLLA films modified with uniaxially oriented high aspect ratio HAp or BT filler particles (Figure S4, Supporting Information).…”

“…A very similar effect was observed when hydroxyapatite (HAp), as a nonelectroactive filler, was used. At high concentrations (5–30 wt%), it was able to affect the crystallization of PLLA, [ 29 ] consequently influencing its piezoelectric response. Since hexagonal HAp does not exhibit piezoelectricity, its contribution was assigned solely to its effect as a filler on the piezoelectricity of PLLA.…”

“…[30,31] This balance can be approached by processing into aligned fiber structures (i.e., wet-spinning, electrospinning, melt-spinning, film-drawing) and/or by adding fillers that serve as nucleating agents. [25,29,32,33] So far different lead-free piezoelectric particles were applied as fillers for designing electrical properties of polymeric matrix, including BaZr x Ti 1−x O 3 and K 0.5 Na 0.5 NbO 3 . [34,35] When used as an electroactive filler during PLLA fiber spinning, a low content (3 wt%) of barium titanate nanoparticles (BT NPs) affected polymer crystallization, inducing a mixture of α and β PLLA phases.…”

Bioelectrets in Electrospun Bimodal Poly(lactic acid) Fibers: Realization of Multiple Mechanisms for Efficient and Long-Term Filtration of Fine PMs

“…This result encourages us to conceive that despite the weak polarity of PLA, the abundant CO groups carried by PLA chains are ready to be polarized with the assistance of hydrogen bonds, especially under the synergistic mechanisms of a high-voltage E-field and electret electrostatic field . It is also of interest to note the generation of the electrospun phase and β-phase crystal by the polarization of HABE, as evidenced by the characteristic peaks at 1360 and 956 cm –1 , respectively. , Generally, the electrospinning-induced amorphous phase and electret-induced crystalline phase could increase the molecular interaction between PLA and HABE and then cause domain alignment at the inorganic–organic interfaces, which significantly facilitated dipole polarization and increased the relative dielectric constant. , …”

“…43,44 Generally, the electrospinning-induced amorphous phase and electret-induced crystalline phase could increase the molecular interaction between PLA and HABE and then cause domain alignment at the inorganic−organic interfaces, which significantly facilitated dipole polarization and increased the relative dielectric constant. 30,45 Taking into consideration that the effect of PLA crystallization behavior dramatically influenced the pyroelectricity performance, we applied DSC measurements to reveal the charge storage mechanism of electrospun HABEmodified PLA. Figure 3e clearly indicates that pure PLA displays a glass transition at 57.9 °C (T g ), a melting endotherm at 153.7 °C (T m ), and a relatively low crystallinity (16.5%) compared to that of compression-molded PLA films after heat treatment.…”