SMA Actuator Multi-Stage Vacuum Shutter
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Solution Overview
Problem
Existing vacuum equipment for charged particle apparatuses, such as scanning electron microscopes, face challenges in efficiently switching between high and low vacuum conditions due to the limitations of traditional motor systems, which can contaminate specimens and obstruct detector views, especially when using vacuum motors that require lubricants or produce particulates.
Innovation Solution
A multi-stage vacuum equipment utilizing a Shape Memory Alloy (SMA) wire actuator to control a perforated shutter with two apertures of varying sizes, aligned by SMA wires or springs, allowing precise adjustment of the aperture to manage pressure changes without exposing the vacuum chamber to air, thus avoiding contamination and maintaining optimal detector access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional vacuum motors are used to control aperture switching, then the aperture can be adjusted between high and low vacuum modes, but the motors contaminate the specimen with lubricants and produce particulates that compromise measurements
Solution Approach 1:
The patent replaces traditional vacuum motors with Shape Memory Alloy (SMA) actuators that use thermal expansion and phase transformation to drive aperture positioning. This substitution eliminates lubricants and particulate generation while maintaining the ability to switch between high and low vacuum modes, directly resolving the contamination issue.
Solution Approach 2:
The invention changes the actuation mechanism from mechanical motor-driven to thermally-actuated SMA elements. By applying electrical current to heat the SMA wires, they undergo phase transformation and expand/contract to position the aperture, changing the control parameter from mechanical rotation to thermal expansion, thereby eliminating contamination sources.
2Quantity of substance
If the objective aperture is reduced to enable low vacuum measurements, then gas flow can be limited, but the field of view is reduced and backscattered electron detection is strongly limited
Solution Approach 1:
The patent implements a dynamic aperture system with multiple selectable openings (first aperture and second aperture) that can be rapidly switched between positions. This allows the system to adapt aperture size dynamically - using a larger aperture for high vacuum measurements to maximize detector sensitivity and field of view, and a smaller aperture for low vacuum measurements to control gas flow, thereby resolving the trade-off.
Solution Approach 2:
The aperture structure is segmented into multiple discrete openings of different sizes (first aperture and second aperture) rather than a single fixed aperture. This segmentation allows selective positioning of different aperture sizes to match different operational requirements, enabling optimal balance between gas flow control and detector performance for each vacuum mode.
3Adaptability or versatility
If the appendage is installed or removed to switch between low and high vacuum modes, then the vacuum regime can be changed, but the chamber must be opened to air and requires long reconditioning time
Solution Approach 1:
The patent pre-positions multiple aperture configurations within the vacuum chamber before operation begins. The SMA actuators are pre-loaded and positioned, allowing instantaneous switching between aperture configurations without requiring chamber opening. This preliminary preparation eliminates the time-consuming reconditioning process associated with physical appendage installation/removal.
Solution Approach 2:
The invention introduces SMA actuators as intermediary elements that enable aperture reconfiguration without direct mechanical intervention or chamber opening. These actuators serve as intermediaries between the control system and the aperture structure, allowing mode switching to occur through thermal actuation rather than physical manipulation, thereby eliminating reconditioning time.
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 seamless switching between high and low vacuum conditions without contaminating the specimen or obstructing detector views, ensuring accurate microscopy measurements while minimizing gas flow and maintaining the integrity of the vacuum environment.
Implementation Method 1
said at least one shutter aperture being aligned and centered with respect to said channel aperture by the actuation of a shape memory alloy element
Implementation Method 2
A first shape memory alloy element may be connected between said support and said perforated shutter to centre said shutter with respect to said channel aperture in a first position in which a first shutter aperture is aligned with said channel aperture
Data Source
AI summary
The present invention relates to a multi-stage vacuum equipment, preferably a two-stage equipment, whose normal operation requires different pressures to be set, wherein the pressure variation may be achieved by a Shape Memory Alloy (SMA) wire movement of a suitable element. The invention further discloses a method for operating said multi-stage vacuum equipment controlled by a SMA actuator.