TEM Vacuum Transfer Assembly for Cryosample Vacuum Integrity
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Solution Overview
Problem
Existing vacuum transfer systems for microscopy, particularly in TEM, face challenges such as expensive and user-unfriendly cryotransfer systems, sample degradation due to ice formation, limited sample size, and poor vacuum integrity, which hinder efficient and reliable cryotransfer and in-situ experiments at low temperatures.
Innovation Solution
A redesigned vacuum transfer assembly comprising a sample holder, vacuum housing, and coupling unit that allows for in-vacuum insertion and maintenance of cryosamples, featuring a wider sample rod for better cooling and stimulus application, and a stiffer xyz stage for improved mechanical stability and resolution, eliminating the need for a secondary airlock and enabling ultra-high vacuum conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a small valve is used in the Dewar to keep the holder weight within acceptable limits, then the holder weight is reduced, but the pumping speed is limited by the valve size
Solution Approach 1:
The vacuum system is divided into two independent pumping paths: one through the small valve near the Dewar for the inner volume, and another through a larger valve in the vacuum housing for the outer volume. This segmentation allows each valve to be optimized for its specific function, maintaining low weight while achieving high overall pumping speed.
Solution Approach 2:
The pumping capability is extended from a single-dimensional valve size constraint to a multi-dimensional solution by adding a second pumping path through the vacuum housing. This creates an additional spatial dimension for vacuum pumping, allowing the system to overcome the limitations of the small Dewar valve.
2Reliability
If a complete cryotransfer system is integrated in a dedicated TEM with a sample holder permanently fitted into a side entry, then cryotransfer capability is achieved, but the system becomes expensive and does not allow in-situ experiments
Solution Approach 1:
The vacuum transfer assembly is designed as a universal interface that can accommodate multiple types of sample holders and experimental configurations. The standardized vacuum housing and coupling unit allow the same TEM to perform both cryotransfer and in-situ experiments by simply changing the sample holder, making the system multi-functional and versatile.
Solution Approach 2:
The system transitions from a static, permanently fitted sample holder configuration to a dynamic, interchangeable sample holder system. The removable vacuum housing and sample holder stage allow flexible reconfiguration for different experimental needs, enabling the system to adapt between cryotransfer and in-situ experiment modes.
3Reliability
If prior art cryotransfer holders are used, then cryotransfer can be performed, but the system is user-unfriendly and allows specimen degradation due to ice formation
Solution Approach 1:
The vacuum housing is evacuated and sealed before the sample holder is inserted, creating a protected vacuum environment in advance. This preliminary vacuum preparation prevents ice formation on the sample during transfer and eliminates the need for complex ice-prevention maneuvers by the user, making the process both reliable and user-friendly.
Solution Approach 2:
The vacuum housing acts as an intermediary chamber that mediates between the atmospheric environment and the TEM vacuum environment. This intermediate vacuum space protects the cryosample during transfer, preventing direct exposure to atmospheric moisture that would cause ice formation, while providing a simple, automated process for users.
4Temperature
If a wider sample rod is used for better cooling and stimulus application, then cooling efficiency and stimulus capability are improved, but the mechanical stability may be affected
Solution Approach 1:
The sample holder is segmented into distinct functional zones: a wider upper section for improved cooling and stimulus application, and a narrower lower section for insertion into the TEM. This segmentation allows the wider rod to provide better thermal and stimulus performance without compromising the mechanical stability required for precise TEM positioning.
Solution Approach 2:
The sample rod has non-uniform geometry with different local qualities: a wider diameter at the sample stage for enhanced cooling and stimulus application, and a narrower diameter at the insertion end for mechanical stability and compatibility with TEM constraints. Each section is optimized for its specific function while maintaining overall structural integrity.
5Manufacturing precision
If a stiffer xyz stage is used for improved mechanical stability and resolution, then image resolution is improved, but the device complexity increases
Solution Approach 1:
The xyz stage and alpha tilt functionality are merged into a single integrated sample holder stage unit. This combination eliminates the need for separate adjustment mechanisms, reducing overall device complexity while maintaining the mechanical stability and precision required for high-resolution imaging through a unified rigid structure.
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
Facilitates easy and reliable cryotransfer of cryosamples while maintaining a good vacuum, allows for larger sample sizes and additional stimuli, and reduces specimen drift, resulting in improved image resolution and longer experimental durations without compromising the TEM vacuum.
Implementation Method 1
a vacuum housing (301) for transfer and vacuum insertion of the sample holder into a sample holder stage
Implementation Method 2
This Dewar is connected to the tip by a cooling rod inside the holder, which transports 'coldness' to the tip of the rod
Data Source
Figure 1a~1c
Figure 1d~1f
Figure 2a~2b
AI summary
The present invention is in the field of a vacuum transfer assembly, such as for cryotransfer, and specifically a TEM vacuum transfer assembly, which can be used in microscopy, a sample holder, a vacuum housing, a sample holder stage and a sample holder coupling unit for use in the assembly, and a microscope comprising said assembly as well as a method of vacuum transfer into a microscope.