Modular Soft Actuator Using Phase-Change Fluid for Fast Cooling

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Solution Overview

Problem

Existing wearable assistive technologies, such as bulky exoskeletons and passive braces, lack portability, efficiency, and fast actuation capabilities, while soft actuators face issues with slow cooling and low bandwidth, making them unsuitable for rehabilitation and assistive robotic devices.

Innovation Solution

A modular soft actuator design utilizing Peltier heating and phase-change fluid volume expansion, where flexible Peltiers are used to rapidly heat and cool a phase-change fluid, enabling fast and efficient actuation through a network of small, portable actuators.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If traditional resistive heaters are used for heating soft actuators, then heating can be achieved, but cooling is passive and slow, resulting in low bandwidth and asymmetrical actuation cycles

Engineering Contradiction:

Improveactuation speedVSAvoidcooling time

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The actuation system is divided into separate heating and cooling functions using two distinct Peltier devices. One Peltier device heats the phase-change fluid while the other simultaneously or sequentially cools it, enabling independent optimization of heating and cooling rates without relying on passive cooling.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system utilizes phase-change fluid that transitions between liquid and gas phases to enable rapid volume expansion and contraction. This phase transition mechanism allows for fast actuation responses while the dual Peltier system manages the thermal cycles efficiently, reducing the time penalty associated with traditional heating-cooling cycles.

Inventive Principle:

Principle #36Phase transitions

2Use of energy by moving object

If shape memory alloys are used for actuation, then high energy density is achieved, but actuation cycles are slow due to heat conversion to mechanical energy

Engineering Contradiction:

Improveenergy densityVSAvoidactuation cycle speed

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The system uses pneumatic actuation through phase-change fluid volume expansion rather than direct thermal-mechanical conversion. The phase-change fluid rapidly expands when heated and contracts when cooled, driving the soft actuator without the slow heat diffusion limitations of shape memory alloys. This pneumatic approach maintains high energy density while achieving much faster actuation cycles.

Inventive Principle:

Principle #29Pneumatics and hydraulics

3Weight of moving object

If wearable assistive technologies are made portable, then wearability is improved, but actuation power and force are reduced

Engineering Contradiction:

Improvedevice weightVSAvoidactuation force

Core Design Contradiction:

Weight of moving objectVSForce

Solution Approach 1:

The phase-change fluid provides rapid volume expansion and contraction that generates high actuation forces in a compact package. This phase transition mechanism enables portable wearable devices to achieve sufficient actuation force without requiring bulky power systems or heavy structural components.

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The soft actuator uses compliant materials with low Young's modulus that can conform to the body while maintaining structural integrity. This composite material approach allows the device to be lightweight and wearable while still generating adequate actuation force through the phase-change fluid mechanism.

Inventive Principle:

Principle #40Composite materials

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 design provides a soft, powerful, and portable actuation system with increased output force and deflection range, suitable for rehabilitation and assistive robotics, overcoming the limitations of existing technologies by enabling rapid actuation cycles.

Implementation Method 1

A modular soft actuator design utilizing Peltier heating and phase-change fluid volume expansion, where flexible Peltiers are used to rapidly heat and cool a phase-change fluid

Methodology Applied

Scientific EffectPeltier heating: Peltier Effect

Implementation Method 2

A modular soft actuator design utilizing Peltier heating and phase-change fluid volume expansion

Methodology Applied

Scientific EffectPhase transition: Phase Change

Data Source

PatentUS12384024B2Thermoactivate modular soft actuator based on phase transition

Publication Date: 2025.08.12 UNIVERSITY OF NORTH TEXAS

AI summary

An actuation device includes a Peltier comprising a first side and a second side; a first module thermally coupled to the first side of the Peltier, and a second module thermally coupled to the second side of the Peltier. The first module is configured to axially contract in response to an increased pressure within the first module and axially expand in response to a decreased pressure within the first module. The second module is configured to axially expand in response to an increased pressure within the second module and axially contract in response to a decreased pressure within the second module.