Microinjection technique: routine system for characterization of microcapillaries by bubble pressure measurement

Area of Science:

• Materials Science
• Fluid Dynamics
• Analytical Chemistry

Background:

• Injection capillaries are crucial for controlled fluid delivery in various scientific applications.
• Accurate characterization of capillary dimensions, particularly the tip inner diameter, is essential for reproducible results.
• Existing methods for determining tip inner diameter may be indirect or tubing-dependent.

Purpose of the Study:

• To establish a reliable method for measuring the inner diameter of injection capillaries.
• To investigate the relationship between bubble pressure and capillary tip dimensions.
• To explore the impact of capillary tip radius on the volume of released fluid.

Main Methods:

• Utilizing five tubing types to pull injection capillaries with varying openings.
• Measuring threshold bubble pressure for each capillary.
• Performing statistical analysis to correlate bubble pressure with tip inner and outer diameters.
• Analyzing the relationship between released volume and capillary tip radius.

Main Results:

• Threshold bubble pressure is a reliable indicator of the tip inner diameter, independent of the tubing used.
• A direct correlation graph between tip inner diameter and bubble pressure is provided.
• Tip outer diameter could not be reliably correlated with bubble pressure due to variations in wall thickness and puller configuration.
• Released fluid volume increases with the fourth power of the capillary tip radius.

Conclusions:

• Bubble pressure offers a robust and universal method for determining injection capillary inner diameter.
• The established relationship between radius and volume is critical for optimizing injection strategies.
• Understanding these parameters allows for the design of more efficient and precise injection capillaries.