Support Surface with Cutouts to Reduce Sitting Pressure and Shear
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Solution Overview
Problem
Single density foam cushions can cause high sitting pressures and shear forces, leading to discomfort and potential tissue breakdown during long periods of sitting.
Innovation Solution
A support surface with cutouts on its bottom surface that provide a controlled structural collapse, reducing peak pressures on the user's ischial tuberosities, and a low-friction interface to reduce shear strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single density foam cushions are used, then durability and cost-effectiveness are improved, but sitting pressure and shear force increase causing discomfort
Solution Approach 1:
The foam cushion incorporates regions of different densities within a single cushion structure. High-density foam is positioned in areas requiring durability and support, while low-density foam is placed in areas contacting the user's body to reduce pressure. This local variation in material properties allows the cushion to simultaneously achieve durability and comfort without requiring multiple separate components.
2Ease of manufacture
If single density foam cushions are used, then manufacturing simplicity is improved, but shear force on user tissue increases
Solution Approach 1:
The cushion uses locally varied foam density to reduce shear force at the interface with user tissue while maintaining structural integrity. The lower density regions near the contact surface allow for greater compliance and reduced friction, thereby minimizing shear force without complicating the manufacturing process.
Solution Approach 2:
The cushion is constructed as a composite material system with multiple foam densities integrated into a single cushion body. This composite approach combines the advantages of different foam types (durability of high-density foam, comfort of low-density foam) while maintaining a unified structure that can be manufactured using standard cushion manufacturing techniques.
3Strength
If higher density foam is used to reduce compression, then structural strength is improved, but comfort decreases due to increased hardness
Solution Approach 1:
The foam cushion incorporates regions of different densities within a single cushion structure. High-density foam is positioned in areas requiring durability and support, while low-density foam is placed in areas contacting the user's body to reduce pressure. This local variation in material properties allows the cushion to simultaneously achieve durability and comfort without requiring multiple separate components.
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 support surface reduces peak pressures by up to 60 mm Hg and minimizes shear strain, allowing users to sit comfortably for longer periods without discomfort or risk of pressure injuries.
Implementation Method 1
The cutouts provide a controlled structural collapse of the support surface by varying a stiffness in a cross-section
Implementation Method 2
The low-friction interface extending across the support surface and the low-friction fabric reduces shear strain in the seating plane of the user
Data Source
AI summary
A support surface including a cutout on a bottom surface of the support surface. The cutout, which can include a set of cutouts, provides a controlled structural collapse of the support surface by varying a stiffness in a cross-section. That is, the area in which the cutouts are positioned collapses more easily than the surrounding area of the support structure, thus making the area with the cutouts perceived as being softer. The cutouts can reduce the peak pressures on the portion of the user's body (for example, the user's ischial tuberosities) that is positioned over the cutouts. The support surface can also include a low-friction interface extending across a top surface of the support surface.