Bilayer Flexible Films with Controllable Porous/Dense Structure via Single-Step Fabrication for Advanced...

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Polyvinylidene fluoride (PVDF) and its copolymers (PVTF) are crucial for piezoelectric energy harvesters and sensors due to their flexibility.
• Existing PVTF materials have limitations in piezoelectric performance, hindering widespread practical applications.
• Microstructural design is key to enhancing the properties of flexible piezoelectric polymers.

Purpose of the Study:

• To develop a novel fabrication technique for high-performance 3D porous PVTF-based flexible piezoelectric films.
• To improve the piezoelectric performance and energy harvesting capabilities of PVTF materials.
• To explore the potential of these films in wearable sensing and energy harvesting applications.

Main Methods:

• A low-pressure-assisted in situ nonsolvent-induced phase separation (LPA-NIPS) technique was developed, modifying the traditional NIPS method.
• Fabrication of 3D porous PVTF films with a bilayer sponge-like structure.
• Control over film thickness and pore size by adjusting nonsolvent (H2O) content.

Main Results:

• The fabricated bilayer sponge-like PVTF films demonstrated superior strain behavior and high electric field tolerance.
• Compared to dense films, the porous PVTF films exhibited a 41% increase in operating voltage (Vop) to 4.58 V at 2500 V polarization.
• The porous films achieved a higher piezoelectric coefficient (d33) of 20.3 pC/N, output voltage of 6.17 V, power density of 1.28 μW/cm², and force sensitivity of 158 mV/N under specific conditions.
• The piezoelectric sensing prototype showed stable performance over 1000 cycles without structural degradation.

Conclusions:

• The LPA-NIPS method successfully produced high-performance 3D porous PVTF flexible piezoelectric films.
• These films offer enhanced piezoelectric properties, making them suitable for energy harvesting from subtle vibrations and wearable sensing.
• The straightforward fabrication process holds promise for large-scale production of advanced piezoelectric materials for active monitoring and healthcare.