Re-Entrant Porous Filter Structures for Liquid Repellency

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Solution Overview

Problem

Existing filtration technologies face challenges in preventing wetting and contamination by liquids without using environmentally unfriendly fluorinated chemicals, particularly in achieving hydrophobicity and oleophobicity.

Innovation Solution

The implementation of re-entrant geometries on porous materials, such as hoodoo structures, which invert the meniscus of a liquid droplet to prevent wetting and maintain porosity, thereby enhancing hydrophobicity and oleophobicity without the need for fluorinated coatings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fluorinated polymer coating is applied to achieve hydrophobicity, then liquid repellency is improved, but environmental harm increases due to use of fluorinated chemicals

Engineering Contradiction:

Improveliquid repellencyVSAvoidenvironmental harm from fluorinated chemicals

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention extracts and removes the harmful fluorinated chemical coating from the system, replacing it with a purely physical re-entrant geometric structure on the porous material surface that achieves liquid repellency through shape rather than chemical composition

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention substitutes the chemical mechanism (fluorinated polymer coating) with a mechanical/geometric mechanism (re-entrant surface structures) to achieve the same liquid repellency function, replacing chemistry with physics-based geometric effects

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If conventional flat porous material surface is used, then manufacturing simplicity is maintained, but liquid repellency and oleophobicity are insufficient

Engineering Contradiction:

Improveliquid and oil repellencyVSAvoidsurface geometry complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention applies curved re-entrant geometric structures (such as inverted cones, spheres, or other curved surfaces) on the porous material surface, where the curvature and overhanging edges create capillary pressure that repels liquids and oils without requiring complex multi-layer constructions

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention changes the surface geometry parameters from flat to re-entrant configurations, specifically controlling the curvature radius, overhang angle, and structure spacing to optimize liquid and oil repellency performance while maintaining manufacturing feasibility

Inventive Principle:

Principle #35Parameter changes

3Productivity

If porous material is used for filtration, then permeability is achieved, but wetting and contamination by liquids occurs

Engineering Contradiction:

Improvefiltration permeabilityVSAvoidresistance to wetting and contamination

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention utilizes the inherent porous structure of the material for filtration permeability while simultaneously applying re-entrant geometric features on the pore surfaces that create liquid-repelling capillary pressures, allowing the material to maintain both porosity and repellency functions

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The invention applies re-entrant geometric structures specifically at the pore openings and surface regions where liquid contact occurs, while the bulk porous structure maintains its filtration permeability, creating local liquid-repelling zones without compromising overall porosity

Inventive Principle:

Principle #3Local quality

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 re-entrant geometries effectively repel liquids, maintaining the permeability and preventing contamination, thus enhancing the material's repellency properties while reducing environmental impact.

Implementation Method 1

The structures have a re-entrant geometry configured to invert a meniscus of a liquid droplet

Methodology Applied

Scientific EffectMeniscus inversion: Surface Tension

Implementation Method 2

achieve hydrophobicity and oleophobicity without the use of fluorinated chemicals

Methodology Applied

Scientific EffectHydrophobicity: Hydrophobe

Implementation Method 3

achieving repellency to oil-based liquids (e.g., oleophobicity) may be desirable in some cases

Methodology Applied

Scientific EffectOleophobicity: Hydrophobe

Data Source

PatentUS20250332551A1Structures having re-entrant geometries on a porous material surface

Publication Date: 2025.10.30 DONALDSON CO INC

AI summary

A filter material has a layer of porous material and a plurality of structures disposed on a surface of the layer, where each of the structures has a re-entrant geometry. The plurality of structures may be a plurality of ordered structures. A filter material may include a layer of porous material and a plurality of re-entrant structures disposed on a surface of the layer, each of the re-entrant structures including a stem and a cap, where the caps of adjacent structures are attached to each other to form a plurality of pores, where each pore is disposed between adjacent re-entrant structures.