Cellulose Nanofiber Honeycomb Structure with Uniform Polygonal Microtubes
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Solution Overview
Problem
Existing honeycomb structures face issues with non-uniformity in the opening shape of microtubes, which affects their strength and uniformity.
Innovation Solution
A method involving unidirectional freezing of a cellulose nanofiber dispersion with controlled light transmittance and concentration, followed by freeze-drying, to produce a honeycomb structure with uniform polygonal microtubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional freezing methods are used to produce honeycomb structures, then the production process is simple, but the opening shape of microtubes is non-uniform
Solution Approach 1:
The invention applies preliminary action by pre-freezing the dispersion medium in a controlled manner before introducing the cellulose nanofiber dispersion. The freezing process is initiated in advance to create a structured ice framework that guides subsequent fiber deposition, ensuring uniform microtube opening shapes. This preliminary structural preparation resolves the uniformity issue without requiring complex real-time control during fiber introduction.
Solution Approach 2:
The invention uses ice crystals formed during controlled freezing as an intermediary structure. The freezing process creates a template of ice columns that act as a mediator between the dispersion medium and the final honeycomb structure. Cellulose nanofibers deposit around these ice intermediaries, which are later removed to leave uniformly shaped microtubes. This intermediary approach enables precise shape control without complex direct manipulation.
2Strength
If the concentration of cellulose nanofiber dispersion is increased to improve structure strength, then the mechanical properties improve, but the light transmittance decreases and uniformity deteriorates
Solution Approach 1:
The invention applies parameter changes by optimizing the concentration of cellulose nanofiber dispersion to a specific range (0.5-2.0 wt%) rather than using high concentrations. This parameter optimization ensures that the dispersion maintains appropriate viscosity and flow characteristics for uniform distribution, while still providing sufficient material for forming strong microtube walls. The controlled parameter range prevents both over-concentration (which causes non-uniformity) and under-concentration (which weakens structure).
Solution Approach 2:
The invention applies local quality by ensuring uniform distribution of cellulose nanofibers throughout the dispersion medium. The controlled concentration and freezing process create consistent local conditions across the entire sample, resulting in microtubes with uniform wall thickness and composition. This local uniformity throughout the structure achieves both strength and shape consistency without requiring high overall concentration.
3Productivity
If rapid freezing is applied to increase productivity, then the production speed increases, but the shape uniformity of microtubes deteriorates
Solution Approach 1:
The invention applies preliminary action by pre-establishing a controlled freezing rate protocol before sample preparation. The freezing rate is predetermined and maintained within a specific range (0.1-10°C/min) throughout the process, eliminating the need for rapid freezing. This preliminary control of the freezing parameter ensures uniform ice crystal formation and subsequent microtube shape consistency while maintaining reasonable production efficiency through standardized procedures.
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 method achieves a honeycomb structure with excellent shape uniformity and mechanical properties, suitable for applications like face masks and air filters.
Implementation Method 1
a water dispersion of a cellulose nanofiber is permitted to unidirectionally freeze at a constant rate
Implementation Method 2
by employing a so-called 'unidirectional freezing method' in which a water dispersion of a cellulose nanofiber is permitted to unidirectionally freeze at a constant rate
Implementation Method 3
followed by freeze-drying, to produce a honeycomb structure with uniform polygonal microtubes
Data Source
AI summary
A honeycomb structure which is an aggregate of a plurality of microtubes comprising a cellulose nanofiber, wherein the microtubes have an opening shape which is polygonal, wherein the ratio of an average long diameter μ2 (μm) to an average short diameter μ1 (μm) (μ2/μ1) is 2.0 or less, when the average long diameter μ2 (μm) is an average of longest diameters of the opening diameters of the individual microtubes, and the average short diameter μ1 (μm) is an average of shortest diameters of the opening diameters of the individual microtubes, and wherein both standard deviations σ1, σ2 for the respective frequency distributions of the short diameter and long diameter in the opening shape of the microtubes are 20.0 μm or less.