Electrification of Sonoluminescing Single Bubble

Area of Science:

• Physical Chemistry
• Acoustics
• Colloid Science

Background:

• Microbubbles in water typically exhibit a negative charge at the liquid-bubble interface.
• Single bubble sonoluminescence (SBSL) involves stable light emission from a single oscillating bubble under acoustic forcing.
• The electrical charge of SBSL bubbles is not well-established and is crucial for understanding their behavior in electric fields.

Purpose of the Study:

• To determine the electrical charge of a single bubble sonoluminescence (SBSL) bubble.
• To investigate the influence of this charge on bubble dynamics and light emission under an applied electric field.
• To explore the factors affecting the charging mechanism of SBSL bubbles.

Main Methods:

• Applying DC voltage to observe the movement of SBSL bubbles relative to a hot electrode.
• Analyzing bubble translation to infer charge and forces acting on the bubble.
• Utilizing light scattering techniques to measure bubble expansion and contraction under electric fields.
• Correlating bubble translation with the elapsed time of sonoluminescence.

Main Results:

• SBSL bubbles were attracted to a hot electrode with negative DC voltage and repelled by it with positive DC voltage, indicating a positive charge.
• Bubble translation occurred to balance electrostatic and primary Bjerknes forces.
• The degree of bubble translation varied with sonoluminescence duration, suggesting internal products influence charging.
• Applied voltage affected bubble size and sonoluminescence intensity: positive voltage decreased them, while negative voltage increased them.

Conclusions:

• Single bubble sonoluminescence (SBSL) bubbles are positively charged.
• The positive charge of SBSL bubbles significantly impacts their electrokinetic behavior and acoustic response.
• Internal chemical reactions within the SBSL bubble contribute to its charging mechanism.