Multi-Layered Prosthetic Suspension Liner with Variable Radial Thickness
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Solution Overview
Problem
Prosthetic suspension liners and sleeves face challenges in conforming to irregular residual limbs, providing adequate pressure distribution, comfort, and durability while accommodating a variety of limb sizes and maintaining strength.
Innovation Solution
A multi-layered suspension liner with a stiffer first elastomeric layer and a softer second layer, combined with a fabric layer, offering variable thickness and radial thickness distribution for improved conformance and cushioning, particularly designed to enhance comfort and stability for amputees by distributing pressure effectively and allowing for easier knee flexion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer elastomeric material is used for the liner, then the manufacturing process is simple, but the liner cannot provide both superior stretching and sufficient strength/durability
Solution Approach 1:
The liner is constructed as a composite structure with an inner layer of softer elastomeric material (higher elongation, lower modulus) bonded to an outer layer of stiffer elastomeric material (lower elongation, higher modulus). This composite construction allows the softer inner layer to provide superior stretching and conformance to the residual limb, while the stiffer outer layer provides structural strength, durability, and resistance to degradation from body fluids.
2Ease of operation
If the liner material is made softer to improve comfort and conformance, then the comfort and conformance improve, but the strength and durability decrease
Solution Approach 1:
The liner combines a softer inner elastomeric layer that provides comfort and conformance with a stiffer outer elastomeric layer that provides strength and durability. The softer material is in direct contact with the residual limb to maximize comfort, while the stiffer material forms the structural outer layer.
Solution Approach 2:
The liner has different material properties at different locations - the inner layer has softer, more compliant material for comfort and conformance where it contacts the residual limb, while the outer layer has stiffer, more durable material for structural support and resistance to external forces and body fluid degradation.
3Ease of operation
If the liner is made thicker to improve cushioning and comfort, then the cushioning improves, but the ability to conform to irregularities decreases
Solution Approach 1:
The liner uses a composite structure where the inner softer layer can deform and conform to irregularities in the residual limb shape, while the outer stiffer layer provides cushioning and structural support. The softer material's compliance allows it to adapt to complex geometries even when bonded to a thicker outer layer.
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 solution provides enhanced comfort, stability, and proprioception, allowing closer contact between the residual limb and the prosthesis socket, improving control and durability while accommodating a range of limb sizes with superior stretching capabilities.
Implementation Method 1
a softer second layer, combined with a fabric layer, offering variable thickness and radial thickness distribution for improved conformance and cushioning
Implementation Method 2
allowing for easier knee flexion... with superior stretching capabilities
Data Source
AI summary
A residual limb suspension liner for a prosthesis has a first layer defined by a first elastomeric material and forms a continuous circumferential internal surface of the liner. The liner also includes a second layer defined by a second elastomeric material different from the first elastomeric material. The second layer has a first surface adjacent to and integrally joined to the first layer. The second layer has a variable radial thickness over an anterior aspect of the liner.