# US 7,744,741 B2 · Method for determining effective diffusivity of substances through porous materials

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- Number: US 7,744,741 B2
- Document ID: US7744741B2
- Status: Granted
- Kind: B2
- Application number: 11/284,811
- Filed: 2005-11-23
- Published: 2006-11-16
- Granted: 2010-06-29
- Earliest claimed: 2005-05-13
- Assignees: National Central University
- Inventors: Jing-Chie Lin; Chien-Ming Lai
- Web page: https://patentgrep.com/patent/US7744741B2

## CPC

- G01N 27/02: by investigating impedance
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

The present invention provides a new method to obtain an effective diffusivity for a certain substance in solutions that diffuse through a porous material. The porous material initially separates two solutions that are different in concentration of the substance. The concentration gradient gives rise to diffusion through the porous material, The concentration change of the substance in the low-concentration compartment is detected through a measurement of the electrochemical impedance data. By means of the measurement, an effective diffusivity coefficient of the substance through the porous material is calculated.

## Claims

### Claim 1

A method for determining an effective diffusivity of a known substance through porous materials, comprising the steps of:
(a) obtaining a first compartment loaded with a permeable solution having a first concentration, and obtaining a second compartment loaded with said permeable solution having a second concentration lower than said first concentration, said permeable solution mixed with a conductive solution;
(b) immersing said porous material in between said first compartment and said second compartment to obtain a concentration gradient of said permeable solution between two ends of each pore of said porous material to diffuse said permeable solution having said first concentration to said second compartment;
(c) setting a probe in said second compartment, said probe connecting to an electrochemical impedance analyzer; and
(d) detecting data signals from the electrochemical impedance analyzer to obtain resistivity at various temperatures and for various times;
using an empirical formula based on a linear relationship of resistivity and concentration and Fick's law so as to obtain a value for an effective diffusivity coefficient of said porous material.

### Claim 2 (depends on 1)

The method according to claim 1, wherein said permeable solution is selected from a group consisting of methanol and ethanol.

### Claim 3 (depends on 1)

The method according to claim 1, wherein said conductive solution comprises a component selected from a group consisting of a salt, an acid, and a base.

### Claim 4 (depends on 1)

The method according to claim 1 wherein said first concentration and said second concentration are in a range between OM (molar, mole per liter) and 20 M.

### Claim 5 (depends on 1)

The method according to claim 1, wherein said conductive solution comprises a concentration between 0.1 M and 2 M.

### Claim 6 (depends on 1)

The method according to claim 1 wherein each said pore comprises an aperture between 1 nm (nanometer) and 100 μm (micrometer).

### Claim 7 (depends on 1)

The method according to claim 1, wherein said porous material is a porous material that has gone through a process selected from a group consisting of a hydrophilic process and a hydrophobic process.

### Claim 8 (depends on 1)

The method according to claim 1, wherein said detecting is performed under a temperature between 10° C. and 80° C.

### Claim 9 (depends on 1)

The method according to claim 1, wherein said method is a non-destructive method in which none of said solution is consumed and no reactant is generated.