Vacuum-Compatible Electrode-Free Poling of PVDF Films Using Glow-Discharge Plasma

Area of Science:

• Materials Science
• Polymer Science
• Surface Science

Background:

• Glow-discharge plasma (GDP) poling is an electrode-free method for activating piezoelectricity in poly(vinylidene fluoride) (PVDF) films.
• The effects of GDP on PVDF properties have been poorly understood despite its proposal decades ago.

Purpose of the Study:

• To demonstrate efficient electrode-free poling of oriented PVDF films using GDP.
• To investigate the relationship between plasma treatment time, structural evolution, and piezoelectric response in PVDF films.

Main Methods:

• Oriented PVDF films were treated using DC glow discharge for durations ranging from 15 seconds to 15 minutes.
• Characterization involved FTIR, DSC, piezoresponse force microscopy, UV-Vis-NIR spectrophotometry, quasi-static d33 measurements, and water contact-angle measurements.

Main Results:

• GDP poling achieved a piezoelectric coefficient (d33) up to ~25 pC/N within 1-5 minutes, with maxima at 1, 2.5, and 5 minutes.
• Plasma treatment increased ferroelectric domain size and surface wettability (water contact angle reduced to 42° within 3 minutes).
• Longer treatment times (>5 min) led to decreased piezoelectric response and optical transparency due to surface degradation.

Conclusions:

• GDP poling offers an effective processing window of 1-5 minutes for PVDF films.
• This electrode-free, vacuum-compatible method enhances surface wettability for applications in flexible piezoelectric sensors and wearable electronics.
• The process allows for subsequent electrode deposition on the activated polymer surface within a single vacuum cycle.