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

Porous structures containing pores at different length scales are often encountered in nature and are important in many applications. While several processing routes have been demonstrated to create such hierarchical porous materials, most methods either require chemical gelation reactions or do not allow for the desired control of pore sizes over multiple length scales.Wedescribe a versatile and simple approach to produce tailor-made hierarchical porous materials that relies solely on the process of 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: 2


Figure: 3


Discussion

To this day the fine points of the electrospinning process are not well understood. However, this was the first publication to document a few very relevant factors, not the leas of which is that the jet instability is one fiber that whips rapidly rather than a family of fibers splitting at point. When all variables are considered, electrospinning becomes exceedingly complex (conductivity of solution, surface charge, flow rate, electric field, etc. THerefore honing in on what is experimentally tractable and fitting it to a model adds substantial value to the discussion of the topic.

Reference

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