The pore size of the smart membranes can be adjusted from the outside: this is very attractive in applications like
biosensors or chemical analysis. The ‘Swiss cheese’ structure is characteristic of many polymer membranes and is now
modified by introducing iron within the polymer. Using an electric signal or a chemical reaction, the pore size can be adjusted. The key to this is controlled adding or extracting of electrons to and from iron.
Thanks to this adjustable pore size, the permeability and selectivity of the membrane can be tuned, for separation purposes or controlled release. The UT scientists see possibilities in analysis and separation of proteins, for example. An extra advantage of the new membranes is the change in colour that takes place. The process of protein detection and analysis becomes visible in an easy way, which may lead to a cheap type of biosensor.
Another application of the smart membrane is in catalysis. Here, it is possible to kill two birds with one stone. Whilst the pore size and permeabiliteit can be altered using a chemical reaction with silver salt, nanosize particles of silver are deposited on the membrane at the same time. Silver is an important catalyst in many applications.
The membrane research is conducted by the Materials Science and Technology of Polymers group, led by Prof. Julius Vancso. This group is part of the MESA+ Institute for Nanotechnology of the University of Twente.
Scientific Summary from Pubmed:
Redox-responsive porous membranes can be readily formed by electrostatic complexation between redox active poly(ferrocenylsilane) PFS-based poly(ionic liquid)s and organic acids. Redox-induced changes on this membrane demonstrated reversible switching between more open and more closed porous structures. By taking advantage of the structure changes in the oxidized and reduced states, the porous membrane exhibits reversible permeability control and shows great potential in gated filtration, catalysis, and controlled release.
Kaihuan Zhang, Xueling Feng, Dr. Xiaofeng Sui, Dr. Mark A. Hempenius and Prof. G. Julius Vancso, Breathing Pores on Command: Redox-Responsive Spongy Membranes from Poly(ferrocenylsilane)s, Angewandte Chemie International Edition, DOI: 10.1002/anie.201408010