2-6 June 2014, 11th International Meeting on Thermodiffusion, Bayonne (France).

I am presenting a talk about my preliminary results on “Synthesis of soft material with intrinsic concentration gradient by thermophoresis”.

In the presence of a temperature gradient, a particle population will experience a thermophoretic force, which will drive particles to regions of high or low temperature, depending on their  thermophoretic behavior. Microfluidic devices, incorporating microchannels with cross-sectional dimensions of a few tens of microns, are ideal to exploit thermophoretic effects since temperature gradients can be established and controlled with high precision (e.g. through the use of micro Joule heaters). In particular by using biocompatible precursors (e.g. sodium alginate), it is possible to create substrates and fibers (high aspect ratio objects) ideal for the study of cellular growth, motility or even diversification.
In the present work a solution of sodium alginate is made to flow in a microchannel with a transversal temperature gradient created by an embedded joule heater and a cold water flow. At the flow focusing
junction the solution meet the buffer (10% dextran in water), and then the gelant solution (0.1M CaCl2 in 10% dextran aqueous solution). At the end of the microfluidic chip the formed hydrogel is extruded and collected. The formed concentration gradient is then frozen via polymerization to create a solid (but soft) substrate that presents a gradient of mechanical properties (e.g. elasticity). Region with different concentration of sodium alginate precursor show different elastic behavior. Therefore a gradient of sodium alginate translate into rigidity modulation.

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