Laser Ablation Cell for High-Resolution ICPMS Imaging
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Solution Overview
Problem
Current laser ablation cells for ICPMS lack the spatial resolution necessary for imaging single cells within tissue samples, due to long aerosol washout times and system dispersion, which limits their application in diagnostic analysis and visualization of cell-to-cell variability.
Innovation Solution
A laser ablation cell design with a 'tube cell' configuration, featuring a flow channel with minimal cross-sectional area variations and a sample chamber positioned close to the flow channel, allowing for laminar gas flow and rapid aerosol transport, reducing washout times to below 30 ms and minimizing dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If external laser ablation cells are used for imaging applications, then scanning of the laser spot becomes feasible and larger samples can be analyzed, but aerosol washout times become too long (seconds instead of milliseconds), limiting spatial resolution
Solution Approach 1:
The ablation cell is divided into multiple flow channels with different functions: a first flow channel for rapid aerosol transport and washout, and a second flow channel for laser beam access through a lateral window. This segmentation allows each channel to be optimized for its specific function, achieving both fast washout and scanning capability
Solution Approach 2:
The laser beam accesses the sample chamber through a lateral window rather than from above, changing the dimensional approach to laser-sample interaction. This lateral configuration allows the laser to scan across the sample while the carrier gas flows rapidly through the channel, achieving both scanning and fast washout
2Measurement precision
If the washout time is extended to allow complete aerosol clearance, then signal overlap between neighboring spots is reduced, but the total scan time increases and resolution improvement is limited
Solution Approach 1:
A carrier gas stream is used to actively transport and rapidly washout aerosol particles from the sample chamber through a optimized flow channel. The pneumatic flow system achieves complete aerosol clearance in milliseconds, much faster than passive diffusion would allow, thereby reducing scan time while maintaining high spatial resolution
3Ease of manufacture
If the flow channel cross-sectional area varies significantly, then the cell design becomes more complex and easier to manufacture, but system dispersion increases and washout time extends
Solution Approach 1:
The flow channel is designed with a substantially constant cross-sectional area along its length, creating a homogeneous flow path. This uniform geometry minimizes turbulence and dispersion, ensuring rapid and efficient aerosol washout while maintaining manufacturing feasibility through standard fabrication techniques
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 design enables high-resolution chemical imaging of biological samples by reducing aerosol washout time and dispersion, allowing for the visualization of individual cells and subcellular structures, enhancing the capability of LA-ICPMS for diagnostic and imaging applications.
Implementation Method 1
a carrier gas stream to transport the ablated aerosol to an inductively coupled plasma (ICP)
Implementation Method 2
ablating material from a sample surface with a laser beam
Implementation Method 3
a sheath gas stream to flush the aerosol axially
Implementation Method 4
the gas is subjected to intense high-frequency electromagnetic fields, which lead to the formation of a plasma by induction
Data Source
Figure 1~2
Figure 3~4(b)
Figure 5
AI summary
A laser ablation cell (1) comprises a flow channel (11) having an essentially constant cross- sectional area so as to ensure a strictly laminar flow in the flow channel. A sample chamber (21) is provided adjacent to a lateral opening (14) of the flow channel. A laser beam (41) enters the sample chamber (21) through a lateral window (16) and impinges on a surface (24) of a sample (23) to ablate material from the sample. The sample may be positioned in such a distance from the flow channel that the laser-generated aerosol mass distribution has its center within the flow channel. This leads to short aerosol washout times. The laser ablation cell is particularly well suited for aerosol generation in inductively coupled plasma mass spectrometry (ICPMS), including imaging applications.