At the end of the project it is the intention to obtain structures, equal or similar to the one of which a cross
section is shown in the adjoining drawing. One type of cells, namely the hepatocytes or liver cells are being
cultured in straight, parallel running microfluidic channels in a central layer. Height and width of the channels
is to be optimised, but is estimated to be around 50μm. Below and on top of the hepatocyte channels
endothelial cells are being cultured in separate channels. These are cells which are resistant to stress, caused by
fluid flow, they are e.g. also constituting the layer in blood vessels, which is in direct contact with the blood
flow. Endothelial cells are smaller than hepatocytes, so height and width of the corresponding channels will
have to be smaller (first estimation around 15μm). The channels with endothelial and hepatocyte cells are
separated by a porous membrane (speckled layers in the drawing). Pores in the membranes should be small
enough to prevent that cells “escape” from their channel to a neighbouring channel, but should be big enough
to permit oxygen and nutrients to diffuse from the endothelial channels to the hepatocyte channels, at least in
the beginning of the culturing cycle. The membranes can be inherently porous, but porosity can also be induced. At the moment it is estimated that pores of 2μm and less will be necessary. The CMST technology requires that it should be possible to apply the microsystem material in the liquid phase, followed by solidification by e.g. curing. The method by which the material is applied (casting, liquid injection moulding, spin coating, etc…) determines the viscosity of the material in its liquid phase. Finally also scenarios for degradation of the substrate material will have to be determined. It is the intention that by the end of the culturing all the substrate material is consumed and disappears, so that only the
bio-artificial cultured tissue remains. Because also the porous membrane disappears, at this moment the
endothelial cells will physically touch the hepatocyte cells, which is also the case in natural liver tissue. It has to be determined how and how fast this biodegradation process has to proceed. All these specifications put limitations to possible materials choices.