Application Cases

Experiment Name: Application of Power Amplifiers in Controlled Fusion of Multi-Component Microdroplets under AC Electric Fields

Experimental Content:
This microdroplet controlled fusion system utilizes electric field force as the driving mechanism for fusion. By employing different electrode designs and waveform configurations, controllable fusion of micro-scale droplets is achieved. The study systematically investigates parameters such as flow rate, component ratio, surface tension, dielectric constant, and electrical conductivity. The research demonstrates that adjusting the electric field conditions enables millisecond-scale droplet fusion under various operational scenarios. Both the fusion region and reaction time can be regulated by the applied voltage and frequency, offering a high degree of controllability.

Research Direction: Controlled Fusion of Microdroplets

Testing Equipment: ATA-7030 High-Voltage Amplifier, Signal Generator, Oscilloscope

Experimental Procedure:
Different types of fluids were injected into pre-designed microchannels. The tubing system was connected using chemically resistant PTFE microtubules to prevent corrosion. The electrical system consisted of a signal generator and a power amplifier (ATA-7030 High-Voltage Amplifier), with an applied voltage range of 0 to 3 kV and a frequency range of 0 to 10 kHz. Image observation was performed using a high-speed camera with a full resolution of 1024 × 1024 pixels at 12,800 fps, combined with a microscope to capture the dynamics of droplet coalescence.

Experimental Results:
The results indicate that both the fusion region and reaction time can be adjusted by varying the applied voltage and frequency. Based on the observed fusion phenomena, two distinct modes of fusion were identified: contact fusion and squeeze-induced coalescence. The latter often occurs at the droplet generation site, where the squeezing effect promotes the fusion process.

Fluid properties such as dielectric constant, electrical conductivity, and surface tension significantly influence fusion behavior:

1. Increasing the relative dielectric constant reduces the threshold voltage for fusion initiation, decreasing it from 250V to 30V.

2. The addition of surfactants narrows the effective voltage range for perfect fusion, enabling selective droplet fusion under different voltage conditions.

3. An increase in electrical conductivity weakens the dielectrophoretic force, raising the threshold voltage for fusion initiation from 400V to 1500V.

Finally, using the above methods, we successfully achieved the controlled preparation of aqueous Janus droplets while maintaining precise control over the fusion conditions.

Figure: ATA-7030 High-Voltage Amplifier Specifications and Parameters