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Perturbations and actuators.

Stimuli-responsive materials aim at reversibly manipulating chemical properties of a system with an external trigger. To achieve such actuations in a biological context, the trigger must be non-invasive and enable remote control and the dynamics of actuation has to be compatible with responses occurring in specific time scale and spatial ranges.

- UV-visible light.(e.g. photocaged inducer of gene expression, photoporation ol lipid membranes)

Light is a particularly attractive trigger for clean and rapid control on specific areas at micrometer scale lengths. Chromophore molecules, e.g. azobenzenes, coumarins, merocyanines,... can be tailored to get highly specific biological responses, including on/off switch of the activity of a protein, gene expression (photo-activated caged inducers of gene expression, photo-poration of membranes, etc … ).

- Magnetic control of the sptaial positioning of biomolecules

Magnetic nanoparticles can be used to generate gradient of molecular concentration that are spatially and temporally flexible. In the context of proteins, they are useful to trigger signaling pathways.

- Thermal modulation

To apply a perturbation that periodically forces a reactive system out-of-equilibrium is an appropriate principle to reveal its dynamics. Temperature is a versatile parameter for periodic excitation. Thermodynamic and kinetic constants of biologically-relevant processes significantly depend on it. In addition, temperature modulations of weak amplitude are non-invasive, compatible with in vivo applications, and easy to implement, either globally (at the scale of a microsystem) or locally (in the close surroundings of a nanoparticle).