Rigid Protective Structure for Atom Probe Tomography of Soft Specimens
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Solution Overview
Problem
Atom probe tomography (APT) is limited in analyzing soft and biological materials due to specimen preparation issues and physical complications, such as asymmetrical field evaporation and high electrostatic stress, which leads to sample disintegration and limited applicability.
Innovation Solution
A method to stabilize soft specimens by surrounding them with a rigid protective structure that only exposes the nanoscale terminus to the electrostatic field, using a nanoscale conical grinder/cutter made of durable materials like diamond, which continually regenerates the tip during analysis, allowing for three-dimensional atomic-scale mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If soft specimens are directly analyzed by APT, then atomic-scale mapping can be achieved, but the specimens disintegrate due to high electrostatic stress and asymmetrical field evaporation
Solution Approach 1:
A rigid protective structure acts as an intermediary between the soft specimen and the harsh APT environment. This structure shields the soft material from direct exposure to high electrostatic stress and vacuum conditions, while allowing field evaporation to occur at the exposed terminus. The protective structure mediates the conflict between achieving atomic-scale analysis and maintaining specimen integrity.
Solution Approach 2:
The protective structure creates a local distinction between the shielded region (soft specimen body) and the exposed region (nanoscale terminus). Only the terminus is exposed to the electrostatic field for field evaporation, while the bulk of the soft specimen remains protected. This local quality approach allows the soft material to maintain stability while still enabling atomic-scale analysis at the exposed tip.
2Productivity
If the entire specimen is exposed to the electrostatic field, then field evaporation can occur, but soft materials experience tip failure due to mechanical stress
Solution Approach 1:
The specimen system is segmented into two distinct parts: the protected soft specimen body and the exposed rigid terminus. The protective structure separates these regions, allowing field evaporation to occur only at the rigid terminus which can withstand the electrostatic stress, while the soft specimen body remains mechanically supported and protected from direct field exposure.
3Reliability
If a protective structure is added to stabilize soft specimens, then specimen stability improves, but device complexity increases
Solution Approach 1:
The protective structure serves multiple functions simultaneously: it provides mechanical support to the soft specimen, shields the specimen from vacuum and electrostatic stress, enables precise positioning of the terminus in the analysis chamber, and facilitates heat transfer during cryogenic cooling. This multi-functionality reduces the need for separate systems and mitigates the increase in device complexity.
4Adaptability or versatility
If conventional APT methods are used for soft materials, then analysis can be performed, but preparation time and costs increase due to specialized requirements
Solution Approach 1:
The protective structure is pre-formed and attached to the soft specimen before APT analysis. This preliminary action includes embedding the soft specimen in a rigid material and shaping the protective structure with the desired terminus geometry. By preparing these components in advance using conventional techniques rather than requiring specialized in-situ preparation during APT, the overall preparation time is reduced while enabling analysis of soft materials.
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
Enables stable field evaporation and accurate reconstruction of soft specimens without tip failure, expanding APT's applicability to biological and polymer samples, reducing costs and time compared to traditional methods.
Implementation Method 1
stabilizing a soft specimen for analysis in an atom probe tomography (APT) environment
Implementation Method 2
enabling three-dimensional atomic-scale mapping of a terminus of the specimen material exposed to an electrostatic field stress of the APT environment through field evaporation
Implementation Method 3
Simultaneously, time-of-flight measurements permit very precise determination of the mass-to-charge (m/z) ratio of individual ions
Implementation Method 4
using a nanoscale conical grinder/cutter made of durable materials like diamond, which continually regenerates the tip during analysis
Data Source
AI summary
Techniques are disclosed for stabilizing soft specimen traditionally considered too fragile for APT instruments. These specimens include biological samples, polymers and other fragile materials. For this purpose, a protective structure is disclosed that surrounds the sides of the specimen by supporting walls while only exposing the very end or terminus of the specimen to the electrostatic field of the APT instrument. The protective structure may take the form of a nanoscale conical grinder which continually machines the specimen to regenerate the terminus of the specimen in-situ. Alternately, the protective structure may take the form of a nanopipette in which the specimen is first frozen before undergoing field evaporation together with the tip of the nanopipette. Heretofore only routinely possible for rigid and hard materials, the design thus extends APT analysis to produce three-dimensional atomic-scale maps of soft specimens.