Phase-Change Nano Relay Using GeTe Volumetric Expansion
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Solution Overview
Problem
Current micro/nanoscale actuators lack efficient, non-volatile solutions for reversible volumetric changes necessary for reliable MEMS/NEMS applications, particularly in relays and robotics, due to limitations in phase change materials.
Innovation Solution
The use of Germanium Telluride (GeTe) as a phase change material in micro/nanoscale actuators, which undergoes reversible transitions between crystalline and amorphous phases, enabling significant volumetric changes through thermal cycling, allowing for the fabrication of non-volatile MEMS/NEMS relays and other devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phase change materials are used in micro/nanoscale actuators, then the actuator can achieve phase transitions, but the materials lack non-volatility and efficient reversible volumetric change
Solution Approach 1:
The patent changes the material parameter by selecting GeTe with specific properties (band gap, phase transition temperature, volumetric change ratio) that simultaneously provide non-volatility and efficient reversible volumetric change. The material parameters are optimized to achieve stable crystalline phase at operating temperatures while enabling large volume changes during phase transitions.
Solution Approach 2:
The patent uses composite structure combining GeTe phase change material with heater electrode and insulator layers. This composite design enables the actuator to achieve both non-volatility (through GeTe's inherent properties) and reversible volumetric change (through the phase transition mechanism in the composite structure).
2Volume of moving object
If phase change material undergoes transition from crystalline to amorphous phase, then volumetric increase of about 10% is achieved, but the transition requires heating to approximately 1000° K which may melt the material
Solution Approach 1:
The patent directly exploits the phase transition phenomenon of GeTe material, which undergoes reversible transitions between crystalline and amorphous phases with approximately 10% volumetric change. The phase transition is induced by controlled heating to approximately 1000° K followed by rapid quenching to achieve the amorphous phase, and subsequent heating to approximately 500° K to return to crystalline phase.
3Reliability
If GeTe is used as phase change material for micro/nanoscale actuators, then non-volatile operation is achieved, but the device complexity increases due to thermal cycling requirements
Solution Approach 1:
The patent replaces complex mechanical actuation systems with a thermal field-based actuation mechanism. By using heater electrodes to induce phase transitions through thermal cycling, the system achieves non-volatile operation without complex mechanical components, simplifying the overall device architecture despite the thermal control requirements.
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
GeTe-based actuators demonstrate up to 10% volume change, enabling reliable unidirectional strain and stable operation at room temperature, facilitating the development of advanced MEMS/NEMS devices with enhanced performance and functionality.
Implementation Method 1
GeTe is a phase change material that can be transitioned from a crystalline phase to an amorphous phase when heated to ̃1000° K (sufficient to melt the material) and quickly quenched
Implementation Method 2
The transition is reversible in nature, as the material undergoes a transition from an amorphous phase to a crystalline phase upon heating to ̃500° K, resulting in a decrease in volume of the material
Implementation Method 3
The device is switched by pulses through the heater. One heater electrode is held at ground while square voltage pulses or another voltage waveform is applied to the other electrode
Implementation Method 4
The cap is a thin insulator that protects the PCM from the atmosphere and reduces reflow of the PCM when in the liquid state
Data Source
AI summary
A MEMS/NEMS actuator based on a phase change material is described in which the volumetric change observed when the phase change material changes from a crystalline phase to an amorphous phase is used to effectuate motion in the device. The phase change material may be changed from crystalline phase to amorphous phase by heating with a heater or by passing current directly through the phase change material, and thereafter quenched quickly by dissipating heat into a substrate. The phase change material may be changed from the amorphous phase to a crystalline phase by heating at a lower temperature. An application of the actuator is described to fabricate a phase change nano relay in which the volumetric expansion of the actuator is used to push a contact across an airgap to bring it into contact with a source/drain.