Research / Recherche

Hydrogel films are networks of hydrophilic polymers cross-linked to each other and grafted onto a substrate. Hydrogel thin films have the advantage of being multi-scale and multi-functional. The network structure provides an additional degree of freedom in the direction perpendicular to the substrate. Hydrogel films therefore allow for greater variability, in terms of thickness, architecture and stimulable properties.

Polymer brushes are the simplest and most effective approach to modify surface properties with a grafted polymer monolayer. We have exploited the two strategies of « grafting from » and « grafting onto » by making the most of either method.

The exploitation of functional properties of grafted hydrogel thin films requires a good understanding of their mechanical properties. Hydrogel films are hydrophilic polymer networks containing a lot of water (up to 80-90% by volume), and therefore fragile. The study of hydrogel films under mechanical and frictional stress or in adhesive contacts allows an understanding of the damage mechanisms and the optimization of the stability and durability of the films.

In the development of new materials and biomaterials, the understanding of adhesion mechanisms in aqueous immersed environments is essential. This requires both a fine characterization (mechanical approach of contact thanks to a probe-tack experimental device) and a good adjustment of the specific molecular interactions (electrostatic interactions, hydrogen bonds, hydrophobic interactions). We study the adhesive properties between synthetic hydrogels and model surfaces functionalized by ad hoc polymer thin films.

Thermo-responsive hydrogels are used as autonomous micro-actuators that are integrated in lab-on-a-chip. Hydrogel microcages swell/collapse on demand with a small temperature change to encapsulate single cells. In our case, the grafting and patterning of the hydrogels are performed before the microfabrication of the chip, which undeniably offers a better control of the synthesis, a better reproducibility and no chemical pollution that prevented a biotechnological breakthrough until now.

Flexible and portable electrochemical biosensors allowing high sensitivity and selectivity of target molecules are developed. A key step in the design of an electrochemical biosensor is the immobilization of bioreceptors on the detection electrode for the molecular recognition of the target. The idea is to use hydrogels as an intermediate layer to increase the density of bioreceptors and the sensitivity of the biosensor. Collaboration with Cyrine Slim, Sophie Griveau and Fethi Bedoui from Chimie ParisTech PSL.

We develop a new generation of photonic crystals with actuatable functions. This is made possible by finely controlling the chemistry and architecture of stimulable hydrogels. The idea is to exploit the platform of nano- and micro-structures of grafted hydrogels to design new photonic crystals in several dimensions: 1D, 2D and 3D. The thermo-responsive properties of hydrogels allow to modulate spectrally on demand the photonic crystals.