Improved preparation of cryogenic sample, e.g. for charged particle microscopy
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Solution Overview
Problem
Existing methods for preparing cryogenic samples for charged particle microscopy often result in inconsistent vitrification, leading to partially damaged samples due to uneven cooling, particularly when using grid-mounted perforated membranes where the backside and frontside receive identical flushes, causing detachment issues.
Innovation Solution
A method involving two conduits for cryogenic fluid that flush the sample from opposite sides with intentionally different cryogenic fluid characteristics, such as type, temperature, flow rate, and duration, to optimize vitrification by creating deliberate asymmetry and reducing mechanical and thermal stress on the sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If identical cryogenic fluid flush is applied to both backside and frontside of the sample, then the cooling process is simplified and symmetric, but sample detachment and damage occur due to uneven stress distribution
Solution Approach 1:
The patent applies asymmetry by intentionally designing different cryogenic fluid flush conditions for the backside and frontside of the sample. The backside receives a stronger, longer-duration flush while the frontside receives a weaker, shorter-duration flush. This asymmetric approach compensates for the structural differences (grid support on backside vs. membrane only on frontside), ensuring uniform stress distribution and preventing sample detachment during vitrification.
Solution Approach 2:
The patent implements local quality by tailoring the cryogenic flush parameters to the specific structural characteristics of each sample side. The backside, supported by a grid, withstands higher flow rates and longer exposure, while the frontside, consisting only of a membrane, receives gentler treatment. This localized optimization of cooling conditions prevents damage while achieving consistent vitrification across the entire sample.
2Manufacturing precision
If rapid cooling is applied to achieve vitrification, then ice crystal formation is prevented, but uneven cooling causes mechanical stress and sample damage
Solution Approach 1:
The patent segments the cooling process into two distinct phases targeting different sides of the sample. The backside undergoes a first cryogenic flush with specific parameters (higher flow rate, longer duration), while the frontside undergoes a second cryogenic flush with different parameters (lower flow rate, shorter duration). This segmented approach allows each side to be cooled at an optimal rate, preventing both ice crystal formation and excessive mechanical stress.
Solution Approach 2:
The patent employs parameter changes by systematically varying key cooling parameters including cryogen type, temperature, flow rate, and flush duration between the backside and frontside treatments. These parameter adjustments are designed to match the thermal and mechanical properties of each sample side, achieving uniform vitrification while minimizing thermal shock and mechanical stress that would otherwise cause sample damage.
3Strength
If grid-mounted perforated membranes are used to hold samples, then sample support is provided, but the backside and frontside have different structural properties leading to detachment issues
Solution Approach 1:
The patent applies preliminary anti-action by anticipating the detachment problem caused by asymmetric structural properties and counteracting it through preemptive asymmetric cooling. Before any damage can occur, the backside receives a stronger flush that accounts for its grid support structure, while the frontside receives a gentler flush appropriate for its membrane-only structure. This preliminary compensation prevents the development of uneven stresses that would lead to detachment.
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 significantly reduces the occurrence of sample damage by tailoring the cooling process to each side, ensuring more consistent and effective vitrification, thereby improving the quality of cryogenic samples for microscopy.
Implementation Method 1
the sample is subjected to rapid cooling using a cryogen
Implementation Method 2
immersing the sample in cryogenic fluid
Implementation Method 3
flush from said mouthpieces
Implementation Method 4
in order to achieve sample vitrification (solidification into an amorphous, glass-like phase)
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A method of preparing a cryogenic sample (e.g. for study in a charged-particle microscope), whereby the sample is subjected to rapid cooling using a cryogen, comprising the following steps: - Providing two conduits for transporting cryogenic fluid, each of which conduits opens out into a mouthpiece, which mouthpieces are arranged to face each other across an intervening gap; - Placing the sample in said gap; - Pumping cryogenic fluid through said conduits so as to concurrently flush from said mouthpieces, thereby suddenly immersing the sample in cryogenic fluid from two opposite sides, wherein the flush of cryogenic fluid applied from a first of said mouthpieces is different - e.g. has a different duration - to that applied from the second of said mouthpieces.