Tapered Capillary Tips With Constant Inner Diameter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for fabricating electrospray ionization (ESI) emitter tips at nanospray flow rates face challenges such as clogging, reproducibility issues, and performance degradation due to thick outer diameters and tapered inner diameters, which affect the stability and reliability of nanospray performance.
Innovation Solution
A method involving the etching of capillary tubes to form tapered tips with substantially equal inner and outer diameters at the orifice, using a concave meniscus etching process that maintains a constant inner diameter and tapers the outer diameter, allowing for the use of etchable materials and fluids that prevent inner wall etching, resulting in self-regulating and reproducible ESI emitter tips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional methods are used to fabricate emitter tips, then the tips can be produced, but the inner diameters decrease along the length of the tip and outer diameters become large (blunt and thick walls), which adversely affects nanospray performance
Solution Approach 1:
The etching process selectively removes material from the outer surface while preserving the inner surface geometry. The capillary is etched in a manner that creates a tapered outer diameter profile while maintaining a constant inner diameter, achieving local differentiation in geometric properties that optimizes both spray performance and clog resistance
Solution Approach 2:
Instead of etching from the inner surface outward (which would compromise inner diameter consistency), the method inverts the approach by etching from the outer surface inward. This allows the inner diameter to remain constant while the outer diameter is selectively reduced to create the desired taper, resolving the contradiction between inner diameter consistency and outer diameter profile
2Ease of manufacture
If tapered inner diameters are used in emitter tips, then the tips can be formed, but this contributes to clogging
Solution Approach 1:
The etching process applies different geometric modifications to different parts of the capillary: the inner surface maintains a constant diameter to prevent clogging, while the outer surface is tapered. This local differentiation ensures that the flow path remains uniform and clog-resistant while still achieving the desired tip geometry
Solution Approach 2:
The method inverts the conventional approach by etching the outer surface rather than the inner surface. This inversion allows tip formation through outer surface modification while preserving the inner diameter, thereby achieving ease of manufacture without compromising clog resistance
3Strength
If thick walls at the orifice are present, then the capillary structure is robust, but this adversely affects nanospray performance
Solution Approach 1:
The etching process creates local quality differentiation by reducing wall thickness specifically at the orifice region through outer surface etching, while maintaining adequate wall strength in the body of the capillary. This localized modification improves nanospray performance without compromising overall structural integrity
Solution Approach 2:
The capillary is effectively segmented into different functional zones: the body maintains sufficient wall thickness for structural strength, while the orifice region undergoes selective etching to reduce wall thickness and improve spray performance. This segmentation allows simultaneous optimization of strength and performance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach produces robust, reproducible ESI emitter tips that resist clogging and maintain stable nanospray performance by ensuring consistent taper angles and diameters, enhancing the reliability and efficiency of ESI-MS systems.
Implementation Method 1
a portion of the capillary tube can be immersed into an etchant, wherein the etchant forms a concave meniscus on the outer surface of the capillary. While etching the outer surface of the capillary wall
Implementation Method 2
While etching the outer surface of the capillary wall, a fluid can be flowed through the interior of the capillary tube. Etching continues until the immersed portion of the capillary tube is completely etched away
Data Source
AI summary
Methods of forming electrospray ionization emitter tips are disclosed herein. In one embodiment, an end portion of a capillary tube can be immersed into an etchant, wherein the etchant forms a concave meniscus on the outer surface of the capillary. Variable etching rates in the meniscus can cause an external taper to form. While etching the outer surface of the capillary wall, a fluid can be flowed through the interior of the capillary tube. Etching continues until the immersed portion of the capillary tube is completely etched away.