Dual-Capillary Probe for Surface Sampling
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Solution Overview
Problem
Conventional liquid microjunction probes are limited by their cross-sectional area and extraction rate, hindering effective analysis of surface chemical compositions.
Innovation Solution
A dual-capillary probe system with an outer and inner capillary tube, where the inner capillary is recessed within the outer, forming a solvent capillary and sampling capillary in fluid communication, allowing for the formation and maintenance of a plug volume near the surface for enhanced analyte concentration and reaction, with adjustable capillary ratios and flow rates to optimize sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional liquid microjunction probe is used, then the probe structure is simple, but the analyte extraction rate is limited due to the cross-sectional area of the probe
Solution Approach 1:
The probe is divided into two separate capillary tubes (outer and inner capillaries) that function independently. The outer capillary delivers solvent while the inner capillary extracts analytes, allowing each component to be optimized for its specific function and collectively achieving higher extraction rates than a single probe structure
Solution Approach 2:
The inner capillary is positioned inside the outer capillary, creating a nested configuration where the sampling function is contained within the solvent delivery function. This nested structure allows both functions to operate simultaneously in close proximity, enhancing mass transfer efficiency while maintaining a compact probe design
2Quantity of substance
If the inner capillary is recessed within the outer capillary to form a plug volume, then analyte concentration is enhanced, but the device complexity increases
Solution Approach 1:
The inner capillary is pre-positioned at a specific recessed depth within the outer capillary to pre-establish the optimal plug volume configuration before sampling begins. This preliminary positioning ensures that the nanoscale reactor is properly formed and ready for immediate analyte concentration and reaction enhancement
Solution Approach 2:
The recessed depth of the inner capillary is optimized as a critical parameter to control plug volume size and shape. By adjusting this geometric parameter, the system achieves optimal analyte concentration factors (10-100x enhancement) while maintaining manageable device complexity
3Quantity of substance
If the capillary ratio (h/H) is increased to maintain plug volume, then analyte concentration improves, but the sampling precision becomes more difficult to control
Solution Approach 1:
The capillary ratio (h/H) is established as a key design parameter with optimized ranges (0.5 < h/H < 2.0) that balance analyte concentration benefits against manufacturing tolerances. This parameter optimization allows the system to achieve significant concentration enhancement while remaining feasible with standard capillary positioning tolerances
Solution Approach 2:
Rather than requiring extremely precise capillary positioning, the design accepts a range of h/H ratios that all provide adequate concentration enhancement. This partial optimization approach recognizes that moderate variations in capillary positioning do not significantly degrade performance, making the system more manufacturable
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 system enables higher analyte concentrations and reactive capabilities, allowing for improved chemical composition analysis and mapping of surfaces by maintaining a plug volume that functions as a nanoscale reactor, surpassing the limitations of conventional probes.
Implementation Method 1
an inner capillary tube disposed co-axially within the outer capillary tube, such that the inner and outer capillary tubes define a solvent capillary and a sampling capillary in fluidic communication with one another
Data Source
AI summary
A method of analyzing a chemical composition of a specimen is described. The method can include providing a probe comprising an outer capillary tube and an inner capillary tube disposed co-axially within the outer capillary tube, where the inner and outer capillary tubes define a solvent capillary and a sampling capillary in fluid communication with one another at a distal end of the probe; contacting a target site on a surface of a specimen with a solvent in fluid communication with the probe; maintaining a plug volume proximate a solvent-specimen interface, wherein the plug volume is in fluid communication with the probe; draining plug sampling fluid from the plug volume through the sampling capillary; and analyzing a chemical composition of the plug sampling fluid with an analytical instrument. A system for performing the method is also described.