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IRTG / Soft Matter Science
Freiburger Materialforschungszentrum
Stefan-Meier-Str. 21
79104 Freiburg, Germany

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You are here: Home Events Dr. Valeriy Luchnikov "Spontaneous folding and rolling of polymer films : an micromechanical phenomenon and a method of microfabrication"

Dr. Valeriy Luchnikov "Spontaneous folding and rolling of polymer films : an micromechanical phenomenon and a method of microfabrication"

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Institut de Science des Matériaux de Mulhouse (IS2M)

What
  • Seminar
When May 31, 2017
from 02:15 PM to 03:00 PM
Where Seminarraum A, FMF, Stefan-Meier-Str. 21, Freiburg
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Thin solid films of arbitrary nature, characterized by a gradient of physico-chemical properties in the direction normal to the films surface, are known to undergo spontaneius curling and rolling, when they are exposed to external stimuli, such as heat, humidity, solvents, etc. This behavior of the films is caused by the bending moment, appearing due to differential volumetric responce of the different layers of the films to the stimuli. A classical example is a bimetallic stripe, which reacts by the change of the curvature radius to temperature variations.  The effect is also well present in the living and non-living matter. For instance,  fallen leaves of certain tree’s species roll up because of different drying rate of the two sides of the leaves.   The process of curling is accopagnied by interesting physical phenomena, such as symmetry breaking and curvature bifurcation of the plates.  Besides the interesting physics, spontaneous curling and rolling was found to be extremely useful as the microfabrication approach for the microfluidics applications, micro-encapsulation,  MEMS/NEMS desing, etc. 

We concentrate our research on polymer self-rolling films, which can be obtained by simple methods such as spin- or dip-coating, or casting.  The self-rolling capacity is imparted to the films by one of the following approaches : (i) formation of bi – or multilayers of chemically distinct polymers, such as polystyrene and poly(4-vinyl pyridine) ; (ii) creation of crosslinking gradients in the direction normal to the films via UV –light or asymmetric exposure of the films to solutions of cross-linking agents ; (iii) selective removal of a filler from one of the layers of  polydimethylsiloxane  bilayer film.  In the cases (i) and (ii), curling is achieved due to differential swelling of the opposite sides of the film in selective solvents (e.g. acidic water, in the case of the P4VP-based films, or DI water for the chitosan-based films).  In the case (iii), the effect is due to gradient tensile strain, provoked by the partial collapse of the elastomer layer, from which the filler was removed. 

The PDMS system is especially convenient for the studies of the curvature distribution over the solid films with spontaneous curvature.  We have found, via the analysis of the 3D-scans of the PDMS plates, that this distribution depends strongly on the shape of the plates. The cylinder-like and the sphere-like deformations can coexist on the same plate after the bifurcation transition. This experimental finding was accompagnied by  computer simulation (particle method).  The polymer-based polymer films are particularly useful for the biomedically oriented applications, due to biocompatibility of the polymers. We have conceived a novel chitosane-based system for the tim-programmed release of macromolecular drugs (like proteins). Such systems can be useful for the growing field of chronotherapies, taking into account the circadian rhythms of a human organism.
 
[1] A Egunov, A Inaba, S Gree, J Malval, K Tamura, Y Saito, V Luchnikov Time-programmed release of fluoroscein isocyanate dextran from micro-pattern-designed polymer scrolls, Journal of Controlled Release, 2016,  233 ,39—47.
[2] A.I. Egunov, J.G. Korvink, V.A. Luchnikov, Polydimethylsiloxane bilayer films with an embedded spontaneous curvature, Soft Matter, 2016, 12 (1) ,45--52
[3] V.A. Luchnikov, Y. Saito, L. Tsanis, A novel fibrous material created by self-rolling of a patterned polymer film, Macromol. Rapid Commun. 2012, 33, 1404-1408
[4] V.A. Luchnikov, L. Ionov, M. Stamm, Self-rolled polymer tubes: novel tools for microfluidics, microbiology and drug-delivery systems, Macromol. Rapid Commun. 2011, 32, 1943-1952

invited by Prof. Günter Reiter

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