Rate-Dependent Stretchable Devices Using Shear Thickening Fluids
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Solution Overview
Problem
Conventional elastic devices, such as knee braces, fail to effectively restrict rapid limb motions that can lead to injuries, particularly in dynamic activities like military operations or sports, due to their inability to provide sufficient resistance at high elongation rates.
Innovation Solution
The development of rate-dependent, elastically-deformable devices that incorporate an elastically-deformable confinement member filled with a fluid, which transitions from a flowable to a non-flowable state at high elongation rates, increasing resistance force and preventing further deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional elastic devices are used, then flexibility and ease of motion are provided, but resistance to rapid deformation is insufficient
Solution Approach 1:
The fluid's viscosity parameter changes dynamically in response to deformation rate. At low elongation rates, the fluid maintains low viscosity allowing flexibility and ease of motion. At high elongation rates, the fluid's viscosity increases dramatically, providing resistance to rapid deformation. This parameter change resolves the contradiction by making the resistance force rate-dependent.
Solution Approach 2:
The fluid undergoes a phase transition from a flowable state to a non-flowable or semi-solid state based on the applied deformation rate. This phase transition enables the device to switch between flexible and resistant states, simultaneously providing ease of operation during normal use and protection during rapid deformation events.
2Reliability
If rate-dependent resistance is implemented, then protection against rapid deformation is improved, but device complexity increases
Solution Approach 1:
The device protects itself against rapid deformation through the inherent rate-dependent properties of the enclosed fluid. No external control systems, sensors, or actuators are needed - the fluid automatically adjusts its resistance based on the deformation rate. This self-service mechanism achieves reliable protection while maintaining relatively simple device structure.
Solution Approach 2:
The invention uses a fluid-filled elastic structure to achieve rate-dependent resistance. The hydraulic principle of fluid incompressibility and viscosity, combined with the elastic confinement member, creates the desired protective effect without complex mechanical linkages or control systems, thus improving reliability while limiting complexity increase.
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
These devices provide enhanced resistance to high-rate elongation, effectively preventing injuries by maintaining flexibility at low rates and stiffening at high rates, thus offering improved protection for joints during rapid movements.
Implementation Method 1
the fluid transforms to a less flowable material that greatly increases the force and energy required for increased elongation; or transforms to a non-flowable material that resists further elongation
Implementation Method 2
The fluid may be a non-Newtonian fluid, in some embodiments, such as a shear thickening fluid (STF)
Implementation Method 3
Rate-dependent, elastically-deformable devices according to various embodiments can be stretched and recovered at low elongation rates
Data Source
AI summary
Rate-dependent, elastically-deformable devices according to various embodiments can be stretched and recovered at low elongation rates. Yet they become stiff and resistive to stretching at high elongation rates. In one embodiment, a rate-dependent, elastically-deformable device includes an elastically-deformable confinement member; one or more filaments placed inside the elastically-deformable confinement member; and a fluid that substantially fills the remaining volume inside the elastically-deformable confinement member. The resistance force to extension of the device is designed to increase as the extension rate of the device increases. At low elongation rates the filaments can readily slide past each other. At high elongation rates, the fluid transforms to a less flowable material that greatly increases the force and energy required for elongation; or transforms to a non-flowable material that resists elongation. The devices thus can be stretched and recovered at low elongation rates, but become extremely stiff and resistive to stretching at high elongation rates.