Absorbent Undergarment Top Layer for Viscous Fluid Intake

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Solution Overview

Problem

Existing washable and reusable absorbent undergarments struggle to effectively manage high volumes of viscous body fluids, particularly menstrual fluids, which tend to aggregate on the surface and cause discomfort due to blood clots and potential leakage.

Innovation Solution

The absorbent undergarment features a top layer with 25-95% open area, including elongated, non-circular openings arranged in a diamond pattern, a wicking layer, and a moisture barrier, designed to quickly absorb and direct viscous fluids away from the surface, enhancing absorption and reducing leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the top layer has a small open area to maintain surface integrity, then surface strength is improved, but the ability to absorb viscous fluids quickly deteriorates

Engineering Contradiction:
Improvesurface strengthVSAvoidfluid absorption speed
Core Design Contradiction:
StrengthVSProductivity

Solution Approach 1:

The top layer is designed with a controlled open area of 25-95% creating a porous structure that enables rapid absorption of viscous menstrual fluids while maintaining sufficient structural integrity. The porous nature allows blood clots and viscous fluids to pass through without the surface collapsing, resolving the contradiction between strength and absorption speed.

Inventive Principle:
Principle #31Porous materials

Solution Approach 2:

The absorbent assembly uses a composite structure with multiple layers including the top layer, wicking layer, absorbent layer, and moisture barrier layer. Each layer has specific properties that complement others, allowing the top layer to have high open area for rapid absorption while the composite structure as a whole maintains durability and surface integrity.

Inventive Principle:
Principle #40Composite materials

2Quantity of substance

If the top layer has a large open area to absorb high volumes of viscous fluid, then fluid absorption capacity is improved, but surface durability deteriorates

Engineering Contradiction:
Improvefluid absorption capacityVSAvoidsurface durability
Core Design Contradiction:
Quantity of substanceVSReliability

Solution Approach 1:

The top layer employs a porous knitted material with 25-95% open area that can accommodate high volumes of viscous fluid absorption. The porous structure is designed to maintain its integrity even at high open areas, preventing surface collapse and maintaining durability through the inherent strength of the knitted construction.

Inventive Principle:
Principle #31Porous materials

Solution Approach 2:

The multi-layer composite structure distributes mechanical stresses across different layers, protecting the high open area top layer from excessive wear while maintaining absorption capacity. The wicking layer, absorbent layer, and moisture barrier layer provide structural support and protection to the top layer.

Inventive Principle:
Principle #40Composite materials

3Strength

If blood clots aggregate on the surface to maintain surface integrity, then surface strength is improved, but user comfort deteriorates

Engineering Contradiction:
Improvesurface strengthVSAvoiduser comfort
Core Design Contradiction:
StrengthVSEase of operation

Solution Approach 1:

The porous top layer with 25-95% open area prevents blood clots from aggregating on the surface by allowing them to pass through the porous structure into the underlying layers. This eliminates the uncomfortable wet feeling on the surface while the porous structure maintains sufficient strength.

Inventive Principle:
Principle #31Porous materials

Solution Approach 2:

The design extracts blood clots and viscous fluids from the surface area by enabling their passage through the top layer into the wicking and absorbent layers below. This removal of clots from the surface improves user comfort while the top layer maintains its structural integrity.

Inventive Principle:
Principle #2Taking out (Extraction)

4Ease of manufacture

If the top layer has parallel rows of holes to simplify manufacturing, then manufacturing complexity is reduced, but directional leakage risk increases

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoidleakage resistance
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent employs a diamond-shaped macro pattern where openings in adjacent rows are offset, creating an asymmetric arrangement. This asymmetric pattern provides more even fluid distribution and reduces directional leakage compared to parallel rows, while still being manufacturable through standard knitting techniques.

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The diamond pattern arrangement distributes openings in a two-dimensional offset grid rather than simple parallel rows. This dimensional arrangement improves fluid distribution across the surface and reduces the risk of flooding in any single direction, enhancing leakage resistance while maintaining manufacturing feasibility.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 allows for efficient handling of high volumes of viscous fluids, minimizing surface wetness and leakage, while maintaining durability and comfort by directing fluids into underlying layers for quick absorption and containment.

Implementation Method 1

The viscous fluid is directed to the layer beneath the top layer, i.e. to the optional wicking layer for further transport to the absorption layer(s)

Methodology Applied
Scientific EffectCapillary action: Capillary Action

Implementation Method 2

at least one absorbent layer located between the top layer and the moisture barrier

Methodology Applied
Scientific EffectAbsorption: Absorption (physical)

Data Source

PatentEP4412571B1Absorbent article
Publication Date: 2026.01.21 ESSITY HYGIENE & HEALTH AB
  • EP4412571B1 patent drawingFigure 1~2
  • EP4412571B1 patent drawingFigure 3~4
  • EP4412571B1 patent drawingFigure 5

AI summary

A washable and reusable absorbent undergarment comprising an absorbent assembly. The absorbent undergarment has an extension in the longitudinal direction and in the transversal direction. The absorbent assembly comprises a wearer facing top layer of a knitted material, an optional wicking layer beneath said top layer, a moisture barrier and at least one absorbent layer located between the top layer and the moisture barrier. The top layer comprises openings therein and the top layer has an open area of 25-95%.