Cryo-Lamella Preparation for Thick HPF Samples Without Shadow Artifacts

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Solution Overview

Problem

Conventional cryo-FIB/SEM workflows face challenges in milling thick specimens with vitrification issues, specimens with preferred orientation, low-throughput when milling small and/or low concentration specimens, and specimens that distribute poorly across grid squares, particularly for samples thicker than 30 micrometers.

Innovation Solution

A method involving angled trench milling and protective layer deposition is employed to prepare lamellae from thick cryogenic samples, utilizing a charged particle beam system with multi-axis sample stages and ion beam-induced deposition to orient and mill samples at various angles, forming lamellae from both surfaces and reducing redeposition artifacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional cryo-FIB/SEM workflows are used to mill thick specimens, then sample preparation can be performed, but vitrification issues and shadow artifacts occur

Engineering Contradiction:

Improvelamella qualityVSAvoidshadow artifacts

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The milling process is divided into multiple segments: first surface milling, sample rotation, second surface milling, and rotation back. This segmented approach allows each surface to be milled independently, preventing shadow artifacts from forming on the opposite side of the lamella.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The conventional single-sided milling approach is inverted by milling both surfaces of the sample. The method rotates the sample 180 degrees after milling the first surface, then mills the second surface, effectively working from both directions to eliminate shadow artifacts.

Inventive Principle:

Principle #13The other way round (Inversion)

2Adaptability or versatility

If the Waffle Method is used for sample preparation, then some challenges are mitigated, but the method is restricted to samples having a thickness of 30 micrometers or less

Engineering Contradiction:

Improvesample thickness rangeVSAvoidvitrification quality

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The method introduces dynamic sample rotation capability, allowing the sample to be tilted and rotated during the milling process. This dynamic adjustment enables the ion beam to mill thick samples from multiple angles, extending the applicable thickness range beyond 30 micrometers while maintaining vitrification quality.

Inventive Principle:

Principle #15Dynamics

3Productivity

If angled trench milling is performed without protective layer deposition, then milling can proceed, but redeposition artifacts increase

Engineering Contradiction:

Improvemilling speedVSAvoidlamella surface quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

A protective layer is deposited on the sample surface before angled trench milling begins. This preliminary protective coating prevents material redeposition during the milling process, ensuring high surface quality on the lamella while maintaining efficient milling speeds.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protective layer acts as an intermediary between the ion beam and the sample surface during angled milling. It captures redeposited material that would otherwise contaminate the lamella surface, allowing aggressive milling angles to be used without sacrificing surface quality.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 the preparation of lamellae from samples thicker than 30 micrometers without shadow artifacts, improving throughput and sample quality for transmission electron microscopy, allowing for efficient and reliable lamella preparation from high-pressure frozen samples.

Implementation Method 1

directing a beam of ions toward a first surface of a sample for a first exposure of the first surface

Methodology Applied

Scientific EffectSputtering: Sputtering

Implementation Method 2

utilizing a charged particle beam system with multi-axis sample stages and ion beam-induced deposition

Methodology Applied

Scientific EffectIon beam-induced deposition: Deposition (physical)

Data Source

PatentUS20260004992A1Lamella preparation from thick HPF samples

Publication Date: 2026.01.01 FEI CO

AI summary

Techniques for preparing a sample are described. A method includes directing a beam of ions toward a first surface of a sample for a first exposure of the first surface. The sample can define the first surface and a second surface, opposing the first surface. The method can include rotating the sample through an angle, β, relative to a beam axis, B of the charged particle beam system, to orient the second surface to receive the beam of ions. The method can include directing the beam of ions toward the second surface of the sample. The method can include rotating the sample relative to the beam axis, B, to orient the first surface to receive the beam of ions. The method can also include directing the beam of ions toward the first surface of the sample for a second exposure of the first surface.