Hierarchical Porous Materials Made by Drying Complex Suspensions

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Wiki Entry by Daniel Rubin, AP225, 11/12/2012

General Information

Authors: Andre R. Studar, Julia Studer, Lei Xu, Kisun Yoon, Ho Cheung Shum, and David A. Weitz

Publication: A. R. Studar, et al. Hierarchical Porous Materials Made by Drying Complex Suspensions. Langmuir, 27, (3) 955-964 February 2011

Key Words: Porous materials, hierarchical, complex suspensions

Summary

Figure: 1

Many natural structures contain pores at varying length scales. Even within our bodies, bones and lung tissue display hierarchically pored materials. Of course, these systems are useful for a variety of applications as well including high-surface area catalytic applications and filtration devices. To synthesize structures like these, people often use gelation reactions of varying chemistries, or foaming processes. However, these techniques do not leave very much freedom to precisely control the location and size of pores, especially not systems with multiple organized pores of different sizes.

Figure: 2

In this paper, the Weitz lab describes a versatile and simple approach to produce hierarchical porous materials. Interestingly, it relies solely on drying. Our results show that simple drying of a complex suspension can lead to the self-assembly of droplets, colloidal particles and molecular species into unique 3D hierarchical porous structures. Using a microfluidic device to produce monodisperse templating droplets of tunable size, we prepared materials with up to three levels of hierarchy exhibiting monodisperse pores ranging from 10 nm to 800 μm. While the size of macropores obtained after drying is determined by the size of initial droplets, the interconnectivity between macropores is strongly affected by the type of droplet stabilizer (surfactants or particles). This simple route can be used to prepare porous materials of many chemical compositions and has great potential for creating artificial porous structures that capture some of the exquisite hierarchical features of porous biological materials.


Figure: 3


Discussion

Reference

A. R. Studar, et al. Hierarchical Porous Materials Made by Drying Complex Suspensions. Langmuir, 27, (3) 955-964 February 2011