Micropatterned surfaces are of considerable importance for microelectronics, printing technology, microfluidic and microanalytical devices, information storage, biosensors, etc. However, once a pattern is generated it cannot be easily changed on the fly. This limits the usability of a patterned surface to a single specific application and new microstructures have to be fabricated for new applications. Therefore it is desirable to develop methods for fabrication of structured surfaces with switchable and rewritable patterns.
The basis of prepared stimuli-responsive surfaces is the site-selective grafting of two oppositely charged polyelectrolytes. Depending on the pH of the surroundings one kind of the polymer chains is swollen (charged and hydrophilic) while the other is collapsed (uncharged and hydrophobic). The main advantage of such surfaces is their capability of inverse switching, for example hydrophilic patterns can be reversibly converted into hydrophobic ones and vice versa, via external stimuli.
The fabrication of micropatterned polymer surfaces, which allow the reversible inversion of surface topography, charge, and wettability is reported. Micropatterned surfaces were prepared by grafting two oppositely charged polyelectrolytes (polyacrylic acid and poly(2-vinylpyridine)) using a combination of photolithography, “lift-off” and “grafting to” techniques.
This approach can be easily extended for the fabrication of multicomponent micropatterned polymer surfaces by repeating the structuring cycle multiple times. We foresee a large potential of inversely switchable micropatterned surfaces for (i) microprinting where topographical features can be switched via external stimuli, (ii) microfluidic devices where liquid movement (direction, speed, etc) can be easily manipulated by pH, and (iii) microanalytical purposes where chemicals and proteins can be deposited in a switchable site-selective manner (programmed protein adsorption).
Synytska, A.; Stamm, M.; Diez, S.; Ionov, L.
Simple and fast method for the fabrication of switchable biocomponent micropatterned polymer surfaces more
Langmuir 23 (2007) 5205-5209
Ionov, L.; Sapra, S.; Synytska, A.; Rogach, A. L.; Stamm, M.; Diez, S.
Fast and Spatially Resolved Environmental Probing Using Stimuli-Responsive Polymer Layers and Fluorescent Nanocrystals more
Advanced Materials 18 (2006) 1453-1457