SMA Actuator Subassembly for Low-Stress Fluidic Valve Closure

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Solution Overview

Problem

Existing fluidic valve actuation systems using shape memory alloy (SMA) wires face challenges in stress distribution and reliability, particularly in micro-fluidic applications, where SMA wires are looped around flexible channels, requiring additional control elements like biasing means or latching mechanisms for efficient closure.

Innovation Solution

A simpler SMA wire actuator subassembly featuring a bendable slender structure with a high slenderness ratio, where the SMA wire is connected to a stationary base with a coupling mechanism that efficiently translates contraction force into bending, eliminating the need for biasing means or latching mechanisms, and allowing for easy integration with multiple actuated elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If SMA wires are looped around flexible channels for valve control, then the valve can be actuated, but high stress is applied to the channel when fully closed

Engineering Contradiction:

Improvevalve actuationVSAvoidchannel stress resistance

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The patent introduces a resilient member as an intermediary between the SMA wire and the valve channel. The SMA wire acts on the resilient member, which in turn acts on the channel, distributing the stress and preventing direct high-stress concentration on the channel walls during full closure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a resilient member with flexible characteristics that can deform elastically under SMA wire actuation. This flexible element absorbs and distributes the mechanical stress, protecting the rigid channel structure from excessive stress while maintaining effective valve closure

Inventive Principle:

Principle #30Flexible shells and thin films

2Reliability

If additional control elements like biasing means or latching mechanisms are added for efficient closure, then valve control is improved, but device complexity increases

Engineering Contradiction:

Improvevalve closure efficiencyVSAvoidactuator structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The resilient member is designed to automatically return to its original position after deformation by the SMA wire, providing self-biasing functionality without requiring external biasing means. The element serves multiple functions including force transmission, stress distribution, and automatic reset, eliminating the need for additional control elements

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent combines multiple functions into the resilient member: it acts as both the actuating element and the biasing mechanism, while also serving as a stress-distributing structural element. This merging of functions achieves efficient valve closure without adding separate biasing means or latching mechanisms

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If SMA wire coupling means are positioned close to the distal end for compact design, then integration is improved, but stress distribution may be affected

Engineering Contradiction:

Improveintegration flexibilityVSAvoidstress distribution

Core Design Contradiction:

Adaptability or versatilityVSStress or pressure

Solution Approach 1:

The patent creates different functional zones along the resilient member: the distal end region near the coupling means is optimized for stress application and transmission, while other regions maintain structural integrity. This local differentiation allows compact coupling positioning without compromising overall stress distribution

Inventive Principle:

Principle #3Local quality

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

This solution provides a reliable, flexible, and efficient actuation system that effectively manages stress distribution, enhancing the functionality and reliability of fluidic valves by utilizing the SMA wire's properties to control the bending of slender structures, thereby simplifying the actuator design and expanding its application in various fluid control scenarios.

Implementation Method 1

two terminals (14) configured to supply current and mechanically fix the extremities of a shape memory alloy wire (13)

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

at least one shape memory alloy wire (13) connected to said two terminals

Methodology Applied

Scientific EffectShape memory alloy effect: Shape Memory Alloy

Data Source

PatentUS11555485B2Shape memory alloy actuator subassembly and fluidic valve incorporating it

Publication Date: 2023.01.17 ACTUATOR SOLUTIONS

AI summary

The present invention is inherent to an actuator subassembly comprising at least one bendable slender structure (12) mounted on a stationary body base (11) and carrying on a first surface an installation feature (17) and a plug (16) in its distal portion, the bending of the slender structure (12) being controlled by a shape memory alloy wire (13) through coupling means (15) located in its distal portion on a second surface opposite to the first surface. The invention also concerns a fluidic valve incorporating such an actuator subassembly.