In microbioreactors we must often provide adequate concentrations of dissolved
oxygen, which is necessary for their functioning or appropriate course of biochemical
reactions. By installing semi-permeable membranes, we can enable very efficient and
continuous transport of oxygen into microreactors made of impermeable materials.
Polydimethylsiloxane (PDMS) predominates among the materials used to make such
membranes. However, the permeability of the membrane can be affected by various
process parameters in its synthesis, namely the mass fraction of crosslinker in the base
matrix of elastomer, thickness of application, polymerization temperature and time and
consequently the final thickness of PDMS membrane. In the present work, several
different PDMS membranes were synthesized under different conditions and
incorporated into microreactors. We compared their efficiency for oxygen permeability
and the association of this parameter with the synthesis conditions. We found that
membranes with greater application thickness are easier to remove from the surface of
the material to which they were applied before polymerization and are also easier to
incorporate into the microreactor. We also determined the final thickness and Young’s
modulus for the membranes. We found that the membrane thickness decreases by half
its application thickness during polymerization and that membranes polymerized at
shorter times are more elastic. PDMS membranes were installed in microreactors, where
the concentration of dissolved oxygen was studied or how well the membrane is
permeable to oxygen. Membranes synthesized under different conditions were
compared with each other. The results of the analysis of the dissolved oxygen
concentration showed that the polymerization time has the greatest influence on the
oxygen permeability, and to a lesser extent the crosslinker content and the
polymerization temperature. At the same time, we also developed a mathematical model
or a simulation predicting the oxygen concentration profile along the length and depth
of the microreactor and comparing the results with experimental data that matched well
and thus confirmed the efficiency of the synthesized PDMS membranes for oxygen
permeability.
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