Vitrified Sample Formation via Cryogenic Droplet Spraying
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for forming cryogenic samples in electron microscopes often result in sample damage due to ice needle formation during rapid cooling, and require complex equipment for vitrification, limiting the efficiency and thickness of the samples that can be prepared.
Innovation Solution
The method involves spraying an aqueous solution onto a cryogenic surface within the evacuated sample chamber of a charged particle microscope, utilizing small droplets that rapidly solidify into amorphous ice, thereby avoiding ice needle formation and enabling in-situ sample preparation with enhanced cooling rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an aqueous solution is sprayed on a cryogenic surface outside the sample chamber, then the sample can be vitrified, but the sample preparation is time-consuming and requires complex equipment transfer
Solution Approach 1:
The invention merges the sample preparation function with the sample chamber by integrating a spray device that can directly deposit aqueous solutions onto the cryogenic sample holder within the vacuum environment. This eliminates the need for separate preparation equipment and time-consuming transfer operations, allowing vitrification to occur in-situ during the imaging session.
Solution Approach 2:
The cryogenic sample holder is pre-cooled to cryogenic temperatures before introducing the aqueous solution. This preliminary cooling action ensures that when the solution is sprayed, it immediately undergoes rapid vitrification upon contact with the pre-chilled surface, eliminating the need for separate cooling steps after sample deposition.
2Ease of manufacture
If the aqueous solution is sprayed in air before vacuum, then sample preparation is simpler, but ice needles form during cooling damaging the sample
Solution Approach 1:
The invention performs the spraying operation within the vacuum environment of the sample chamber, which acts as an inert atmosphere preventing ice crystal formation. The vacuum environment eliminates air moisture that would otherwise freeze into damaging ice needles during the cooling process, while still allowing the aqueous solution to be deposited and vitrified on the cryogenic surface.
Solution Approach 2:
The invention utilizes controlled phase transition by spraying the aqueous solution as a fine mist that rapidly transitions from liquid to amorphous solid state upon contact with the cryogenic surface. This controlled phase change occurs in the vacuum environment, preventing the formation of crystalline ice structures and achieving vitrification without ice needle damage.
3Ease of operation
If the sample is prepared outside the vacuum chamber, then preparation can be done in air, but the sample must be transferred which risks ice growth
Solution Approach 1:
The invention combines the sample preparation and imaging environments by integrating the spray device within the vacuum chamber. This allows the entire sample preparation process to occur in-situ under vacuum conditions, eliminating the need for transferring samples between chambers and the associated risks of ice growth during transfer.
4Device complexity
If conventional spraying methods are used, then equipment is simple, but cooling rate is insufficient for vitrification
Solution Approach 1:
The invention segments the aqueous solution into fine droplets or mist before spraying onto the cryogenic surface. This segmentation dramatically increases the surface area-to-volume ratio of the sample, enabling much faster heat transfer and cooling rates that achieve vitrification. The simple spray device creates this segmentation through aerosolization, maintaining equipment simplicity while achieving the required cooling speed.
Solution Approach 2:
The invention relies on the phase transition from liquid to amorphous solid occurring rapidly upon contact with the cryogenic surface. The phase change itself provides the mechanism for ultra-fast cooling, as the latent heat of fusion is rapidly removed by the cold surface, achieving vitrification rates sufficient to prevent ice crystal formation without complex cooling equipment.
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 allows for quick and effective formation of vitrified samples with improved cooling rates, preventing ice needle damage and enabling the preparation of thicker samples in a vacuum environment, suitable for high-resolution imaging.
Implementation Method 1
the droplets cool fast enough to solidify in the form of amorphous ice
Implementation Method 2
solidify to form a vitrified sample
Data Source
AI summary
The invention relates to a method of forming a vitrified sample on a sample holder (112) for inspection in an electron microscope (100, 106). It is known to spray a solution on a grid and then immerse the grid in a cryogenic liquid, such as ethane or liquid nitrogen. The invention proposes to spray (via 118) small droplets of the liquid on a cryogenic surface (112), such as a grid or a sample holder in vacuum. The liquid forms vitrified sample material (200, 202) when hitting the surface due to the low temperature of the grid or sample holder. A lamella may be excavated from the thus formed sample material, to be studied in a TEM, or the vitrified sample material may be directly observed in a SEM. In an embodiment the material may be sprayed on a cryogenic liquid, to be scooped from the liquid and placed on a grid.