Interconnectivity imaged in three dimensions: Nano-particulate silica-hydrogel structure revealed using electron...

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Particulate hydrogels are vital in controlled release, food science, batteries, and biomedical applications.
• Understanding transport properties necessitates detailed knowledge of pore structure and 3D interconnectivity.
• Existing 2D methods cannot fully capture the complex pore network.

Purpose of the Study:

• To reveal the detailed three-dimensional structure of particulate hydrogels using Electron Tomography (ET).
• To investigate the nanostructure of particle and pore networks in 2D and 3D.
• To compare the interconnectivity and accessible pore volume fraction as a function of pore size in different hydrogels.

Main Methods:

• Electron Tomography (ET) was employed to visualize hydrogel nanostructures.
• High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) was used for image acquisition.
• Three different silica hydrogels with varying particle and pore sizes were analyzed.

Main Results:

• ET provided detailed 3D insights into pore network interconnectivity and channel width distribution.
• Significant differences in accessible pore volume fraction were observed between hydrogels, especially when considering 3D data.
• The finest gel showed over 90% accessible pore volume in 2D, but all gels had 30-40% in 3D.

Conclusions:

• Three-dimensional pore interconnectivity is critical for accurate assessment of hydrogel transport properties.
• ET offers a superior method for characterizing complex hydrogel nanostructures compared to 2D techniques.
• Hydrogel pore structure significantly influences accessible volume and transport, with 3D analysis revealing nuances missed by 2D.