Textured Fiber Fabrication via Preform Encapsulation

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Solution Overview

Problem

Current methods face challenges in fabricating high-quality sub-micrometer patterns on large-area, flexible, and curved surfaces, as well as within confined channels, due to thermal reflow and structural deformation during the thermal drawing process, which limits the creation of functional materials with prescribed functionalities.

Innovation Solution

A novel approach using a preform-to-fiber thermal drawing technique with a textured preform encapsulated in a low-interfacial-energy polymer, allowing for the preservation of sub-micrometer feature sizes by reducing Laplace pressure and enabling the use of functional polymers for mechanical actuation, such as touch sensing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If thermal drawing process is used to fabricate fibers, then large-area and flexible surfaces can be achieved, but thermal reflow and structural deformation occur causing loss of sub-micrometer pattern quality

Engineering Contradiction:
Improveflexibility of surfaceVSAvoidsub-micrometer pattern quality
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary anti-action by encapsulating the textured preform in a sacrificial polymer layer before thermal drawing. This protective layer counteracts the thermal reflow and surface tension forces that would otherwise deform the sub-micrometer patterns during the heating process, preserving pattern quality while enabling flexible fiber fabrication

Inventive Principle:
Principle #9Preliminary anti-action

Solution Approach 2:

The sacrificial polymer layer acts as an intermediary between the textured preform and the thermal drawing process. It provides mechanical support and thermal protection during fabrication, allowing the patterns to survive the thermal processing while enabling the fiber to be drawn into flexible configurations

Inventive Principle:
Principle #24Intermediary (Mediator)

2Length of moving object

If thermal drawing is performed at high temperature, then fiber can be drawn into long and thin structures, but Laplace pressure causes thermal reflow that degrades sub-micrometer features

Engineering Contradiction:
Improvefiber lengthVSAvoidfeature size
Core Design Contradiction:
Length of moving objectVSManufacturing precision

Solution Approach 1:

The sacrificial polymer layer is applied before thermal drawing to preemptively counteract the Laplace pressure effects. During high-temperature drawing, this layer maintains the structural integrity of sub-micrometer features, preventing thermal reflow while allowing the fiber to be drawn to great lengths with preserved pattern quality

Inventive Principle:
Principle #9Preliminary anti-action

Solution Approach 2:

The patent creates a composite structure combining the textured preform material with a sacrificial polymer layer. This composite approach allows the fiber to withstand high-temperature drawing processes while maintaining sub-micrometer feature precision, as the polymer layer provides additional structural support during the drawing process

Inventive Principle:
Principle #40Composite materials

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

Enables the creation of textured fibers with sub-micrometer feature sizes on flexible and curved surfaces, maintaining structural integrity and allowing for applications in enhanced hydrophobicity, optical properties, and pressure sensing, while also enabling the use of textured fibers as molds for micro-channels and MEMS devices.

Implementation Method 1

the textured preform is heated up above its glass transition temperature and deforms plastically at high viscosity into a long and thin fiber or ribbon

Methodology Applied
Scientific EffectGlass transition:

Implementation Method 2

the desired texture is encapsulated within a second material (for example a polymer) with a low interfacial energy. This slows down drastically the velocity field induced by Laplace pressure

Methodology Applied
Scientific EffectLaplace pressure: Surface Tension

Data Source

PatentEP3377681B1Fabrication method of functional micro/nano structures over large-area, flexible and high curvature surfaces, by drawing a fiber from a preform
Publication Date: 2020.12.30 ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (EPFL)
  • EP3377681B1 patent drawingFigure 1
  • EP3377681B1 patent drawingFigure 2
  • EP3377681B1 patent drawingFigure 3~4D

AI summary

The method for drawing a fiber with a textured surface comprises the following steps: - forming of a preform from which the fiber is to be drawn with a textured surface; - addition of an outer layer to the textured preform to preserve the shape of the texture of the preform surface during the drawing operation; - drawing of a fiber from the preform, whereby the fiber keeps the formed texture of the preform surface and - removing the additional outer layer to leave the original surface textured fiber exposed. The obtained fiber can be used as a mold to form a textured hollow channel in another material, as a surface coating and as a pressure detector.