Functional surfaces in microfluidic systems

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Microfluidic structure (cryoprint) printed on an electrode
Raster electronic image of a printed microfluidic structure (inverse polymer imprint, cryoprint)
Microfluidic chip (cryoprint)

Cryoprint

Principle of cryoprinting as a special case of UV replication of ice microstructures:

Microdroplets of an aqueous solution from a pressure nozzle are applied to an ice-cooled surface, which immediately freeze on contact and form a three-dimensional basic structure. Three-dimensional ice microstructures can be written by a relative movement of the pressure nozzle and the surface. These ice microstructures can be embedded in a polymer matrix by coating them with a liquid UV-curing formulation and polymerizing them chemically by radiation. When the temperature increases, the written ice microstructures thaw and leave an "inverse imprint" in the polymer matrix. If flat glass or silicon substrates are used as an ice-cooled surface, corresponding microfluidic chip structures can be obtained. The advantages of this process are the ability to produce and test microfluidic prototypes very quickly and to produce them in small series. In addition, topographic and chemical functionalities can be generated within the printing process by using aqueous solutions of radiation-polymerizable substances capable of forming so-called cryogels as "printing inks". The printing conditions are optimal for many biologically active substances.

3D functional mocrofluidic printing