Mechanically Responding Functionalized Polyelectrolyte Multilayer Films

The alternate deposition of polyanions and polycations on charged surfaces leads to the formation of nanostructured films called polyelectrolyte multilayers [1,2,3]. The layer by layer deposition process of polyelectrolytes is used to design films equipped by compartments containing "free" polymers or biomolecules [4-6]. Each compartment corresponds to a stratum of an exponentially growing polyelectrolyte multilayer film and two consecutive compartments are be separated by a stratum composed of linearly growing multilayers that act as a barrier preventing biomolecule diffusion from one compartment to another. Such multicompartment films are now built up on an extensible silicon sheet to design stimuli responding films. Nanometer-sized multilayer barriers deposited on or between multilayer compartments will act as nanovalves [7]. For the investigated system, the stretching induces the formation of nanopores in the barriers once a critical stretching degree is reached and consequently allows a diffusion process through the barrier of polyelectrolyte chains initially contained in the different compartments. This critical stretching degree depends upon the number of bilayers constituting the barrier [8]. Finally, the diffusion of polyelectrolytes through the barrier from one compartment to another can be switched on/off by tuning the mechanical stretching and thereby opening or closing nanopores in the barrier. Compartments functionalized with enzymes allow the design of biocatalytic surfaces. Our goal was to finely tune the kinetic parameters (rates, delays, pulses...) of the enzymatic reactions by means of mechanical stimuli. This will represent a first step toward the design of chemically or biologically active films responding to mechanical stresses and applications are foreseen in the field of biopatches or biosensors