Fluidic Artificial Muscle Structure Using Vacuum-Driven Contraction
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Solution Overview
Problem
Current artificial muscles face challenges in achieving high-performance, low-cost fabrication, complex actuation, and scalable implementation, with limitations in contraction ratios, energy efficiency, and operational safety due to their material properties and structural constraints.
Innovation Solution
The development of a fluidic artificial muscle system comprising a collapsible skeleton and flexible skin, where pressure changes within a sealed volume drive actuation, utilizing a fluid displacing, releasing, or capturing mechanism to create pressure differentials, allowing for multi-axial complex motions and controllable sequential movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If shape-memory alloys are heated above phase transition temperature to generate large contractile stress, then stress generation is improved, but cycle time increases and hysteresis occurs
Solution Approach 1:
The patent replaces thermal-driven shape-memory alloy actuators with fluid-driven artificial muscles. The fluid-driven system uses pneumatic or hydraulic pressure to inflate elastomeric membranes, generating mechanical force without thermal phase transitions. This substitution eliminates hysteresis and reduces cycle time while maintaining high contractile stress capability.
Solution Approach 2:
The patent employs pneumatic or hydraulic fluid pressure to drive the artificial muscle actuators. By inflating elastomeric membranes with pressurized fluid, the system generates large contractile forces rapidly and reversibly, achieving fast cycle times without the hysteresis problems inherent in thermal-driven SMA systems.
2Force
If high-pressure fluid is used to drive McKibben actuators to achieve large force and displacement, then actuation performance is improved, but operational safety deteriorates
Solution Approach 1:
The patent inverts the traditional positive-pressure approach by using negative pressure (vacuum) to drive the artificial muscles. Instead of pressurizing the internal fluid to generate force, the system creates a vacuum inside the elastomeric membrane, allowing external atmospheric pressure to collapse the structure and generate contractile motion. This inversion dramatically improves operational safety by eliminating high-pressure fluid hazards.
Solution Approach 2:
The patent converts the typically harmful effect of vacuum (which can cause structural collapse) into a beneficial actuation mechanism. By designing the elastomeric membrane and skeleton structure to controllably collapse under vacuum, the system generates useful mechanical work while operating at inherently safe negative pressures rather than dangerous positive pressures.
3Force
If elastomeric structures are designed to withstand high positive pressure, then force generation is improved, but maximum contraction is limited to approximately 36%
Solution Approach 1:
The patent uses negative pressure (vacuum) instead of positive pressure to drive actuation. This inversion allows the elastomeric membrane to collapse inward more completely, enabling contraction ratios exceeding 90% compared to the ~36% limit of positive-pressure actuators. The vacuum-driven approach removes the structural constraints that limit contraction in traditional McKibben actuators.
4Adaptability or versatility
If complex actuation mechanisms are implemented to achieve multi-axial motions, then motion capability is improved, but device complexity increases
Solution Approach 1:
The patent divides the artificial muscle into segmented components: an elastomeric membrane, a collapsible skeleton with articulated joints, and fluid distribution channels. This segmentation allows independent optimization of each component and enables complex multi-axial motions through coordinated deformation of simple segments, rather than requiring a monolithic complex mechanism.
Solution Approach 2:
The patent enables multi-axial motions by allowing the elastomeric membrane to deform in multiple dimensions simultaneously. The collapsible skeleton with its articulated structure permits contraction, expansion, bending, and twisting motions by coordinating fluid pressure distribution across different regions of the membrane, achieving versatile motion capability through dimensional deformation rather than mechanical linkages.
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 system achieves fast, powerful, and energy-efficient actuation with high contraction ratios and stress generation, comparable to natural muscles, while being scalable and cost-effective, with the ability to produce peak power densities over 2 kW/kg and energy efficiencies of 59%.
Implementation Method 1
a fluid displacing, releasing, or capturing mechanism configured to increase or decrease fluid pressure inside the sealed volume
Implementation Method 2
the flexible skin and skeleton are configured for the flexible skin to provide a pulling force on the collapsible skeleton with a pressure change in the sealed volume
Implementation Method 3
These temperature changes, which increase or decrease the pressure of the internal fluid in the sealed volume, can be achieved through both physical methods
Implementation Method 4
an electrical heating system can be used to increase the temperature via, e.g., resistive heating
Implementation Method 5
phase changes between solid, liquid, and gas of the fluid can also be used to produce pressure changes via, for example, condensation, solidification, and deposition, etc.
Data Source
AI summary
An artificial muscle system includes a collapsible skeleton, a flexible skin, and a muscle actuation mechanism. The collapsible skeleton is contained inside a volume defined, at least in part, by the flexible skin. The flexible skin and the collapsible skeleton are configured for the flexible skin to provide a pulling force on the collapsible skeleton when a pressure difference exists between the inside of the sealed volume and a surrounding environment to change at least one of the dimensions and thus geometry of the collapsible skeleton. The muscle actuation mechanism includes at least one of the following to deploy or contract the collapsible skeleton: (a) a fluid displacing, releasing, or capturing mechanism configured to increase or decrease fluid pressure inside the sealed volume; and (b) a heating or cooling element configured to change the temperature of fluid in the sealed volume.