Cryogenic Specimen Holder With Retractable Tip for High-Tilt Imaging
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Solution Overview
Problem
Existing cryogenic specimen holders for transmission electron microscopy suffer from vibrations, drift, and thermal stress issues due to rigid thermal contacts and limited tilt angles, which compromise image resolution and specimen stability during low-temperature imaging.
Innovation Solution
A cryogenic specimen holder design featuring a Dewar with flexible thermal conductor ribbons and a retractable cartridge, allowing for stable thermal contact and vibration damping, enabling tilt angles up to ±80° while maintaining continuous cooling medium contact and preventing liquid nitrogen spillage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If rigid thermal contacts are used to maintain thermal connection between Dewar and specimen holder, then thermal stability is improved, but vibrations and drift increase compromising image resolution
Solution Approach 1:
The patent employs a flexible thermal ribbon instead of rigid thermal contacts to connect the Dewar to the specimen holder. This flexible ribbon maintains thermal connection while accommodating movements and reducing vibration transmission, thereby preserving image resolution during cryogenic imaging operations.
Solution Approach 2:
The patent introduces a dynamic adjustment mechanism that allows the thermal connection to adapt during tilting operations. The system can adjust the thermal path length and contact pressure dynamically, maintaining optimal thermal stability while minimizing vibrations at different tilt angles up to ±80°.
2Adaptability or versatility
If the holder is tilted to higher angles for 3D imaging, then imaging versatility is improved, but liquid nitrogen spillage and gas trapping occur
Solution Approach 1:
The patent designs the Dewar with a curved bottom surface that follows a circular arc. This curvature ensures that the liquid nitrogen remains in contact with the thermal ribbon at the lowest point of the arc during tilting, preventing spillage and gas trapping while enabling tilt angles up to ±80°.
Solution Approach 2:
The patent repositions the thermal ribbon attachment point from the traditional bottom center to the lowest point of a circular arc. This dimensional repositioning allows the thermal connection to remain effective at various tilt angles while preventing liquid nitrogen from migrating away from the thermal contact point.
3Strength
If rigid structural support is used for the specimen holder, then mechanical strength is improved, but thermal gradients and physical stresses increase
Solution Approach 1:
The patent segments the thermal conduction path into multiple flexible ribbon sections rather than using a single rigid structure. This segmentation allows each section to independently accommodate thermal expansion and contraction, reducing thermal gradients and physical stresses while maintaining overall structural integrity.
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
The design significantly reduces specimen drift and vibrations, ensuring stable operating conditions and improved image resolution by minimizing thermal gradients and maintaining consistent cooling, even at high tilt angles.
Implementation Method 1
The Dewar is constructed as a conventional vacuum flask with an interposed partial vacuum between an inner liquid support vessel and an outer protective housing
Implementation Method 2
A set of thermal conductor ribbons, braids or the like, preferably flexible, including combinations thereof, are incorporated into the thermal transfer system which extracts heat from the specimen
Implementation Method 3
Each of the thermal ribbons, for example, in the preferred embodiment, forms a vibration damper between the various components of the cooling assembly
Implementation Method 4
The cooling medium is utilized to remove the heat from the specimen support and specimen to maintain the same at the necessary low temperature
Data Source
AI summary
An improved cryogenic specimen holder for imaging and analysis facilitates imaging at very high tilt angles with a large field of view. A retractable specimen holder tip protects the specimen during transport. An optimized Dewar design is positioned at a fixed, tilted angle with respect to the axis of the holder, providing a means of continuously cooling the specimen irrespective of the high tilt angle and amount of liquid nitrogen present in the vessel. The Dewar neck design reduces entrapment of nitrogen gas bubbles and its shape prevents the spilling of liquid nitrogen at high tilt angles. The specimen holder has a retractable tip that completely encapsulates the specimen within a shielded environment internal to the specimen holder body. The cooling and specimen transfer mechanisms reduce thermal drift and the detrimental effects of vibrations generated by both the evaporation of liquid nitrogen present in the Dewar and other environmental effects.