Shape-Memory Alloy Switch With Self-Latching Metallic Contacts
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Solution Overview
Problem
Existing electrically-operated switches, such as electromagnetic relays and semiconductor switches, require holding power to maintain the switch state and suffer from higher power losses due to higher contact resistance at semiconductor junctions compared to metallic contactors.
Innovation Solution
A shape-memory alloy actuated switch (SMAAS) that uses a shape-memory alloy in a protagonist-antagonist configuration to change switch states without holding current, leveraging self-heating SMA actuators to alter physical characteristics and reduce power loss by utilizing metallic contacts with lower resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If electromagnetic relays or semiconductor switches are used, then switching function is achieved, but holding power is required to maintain switch state
Solution Approach 1:
The patent replaces electromagnetic or electronic switching mechanisms with a shape memory alloy-based mechanical switching system. The SMA actuator undergoes a phase transformation when heated, generating mechanical force to move the switch contact between open and closed states. Once actuated, the mechanical configuration is self-latching and requires no holding power to maintain the switch state, thereby eliminating continuous energy consumption while preserving reliable state maintenance.
Solution Approach 2:
The patent utilizes the phase transition properties of shape memory alloy materials. When the SMA actuator is heated above its transformation temperature, it transitions from a martensitic phase to an austenitic phase, causing a change in shape that drives the switch contact. This phase transition enables the actuator to generate sufficient mechanical force for switching without requiring continuous power input to maintain the switched state.
2Loss of energy
If semiconductor switches are used, then switching function is achieved, but power losses are higher due to higher contact resistance at semiconductor junctions
Solution Approach 1:
The patent replaces semiconductor-based electronic switching with a mechanically actuated switching system using shape memory alloys. The switch contact is formed by direct mechanical contact between conductive elements, eliminating the semiconductor junctions that cause high contact resistance and power losses. This mechanical contact approach achieves low power loss comparable to traditional metallic contactors while maintaining reliable switching function.
Solution Approach 2:
The patent employs a composite structure combining shape memory alloy actuators with traditional metallic switch contacts. The SMA provides the actuation mechanism while the metallic contacts provide low-resistance electrical pathways. This composite approach leverages the advantages of both materials: the smart material properties of SMA for actuation and the excellent electrical conductivity of metals for current carrying, thereby reducing overall power losses.
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 SMAAS achieves stable switching with reduced power consumption and lower power losses, eliminating the need for holding current and offering improved efficiency compared to traditional switches.
Implementation Method 1
The one or more shape-memory alloy actuators are self-heated by passing current through the shape-memory alloy material
Implementation Method 2
Shape memory alloys (SMAs) are smart materials that can be set to a specific shape and remember this shape even after undergoing a plastic deformation at a low temperature. Heating SMAs above a certain temperature, termed the austenitic transformation temperature, forces the material to return to its original set shape. A significant force is generated by the material while reverting shape.
Data Source
AI summary
A shape-memory alloy actuated switch (SMAAS) is provided that enables the stable switching of two separate circuits. The presently disclosed SMAAS includes a substrate, one or more electrical contacts attached to the substrate for connecting to load circuits, and one or more electrically conductive elements for selectively connecting the one or more electrical contacts. The disclosed SMAAS also includes one or more shape-memory alloy actuators attached to the substrate. The one or more shape-memory alloy actuators are configured to move the one or more electrically conductive elements. The shape-memory alloy actuators are self-heated by passing current through the shape-memory alloy material. The disclosed SMAAS may also include electrical contacts to connect an external control current to the shape-memory alloy material. In some examples, the provided SMAAS includes one or more retention mechanisms to prevent movement of the electrically conductive elements after actuation.