Controlling the Self-Spreading Dynamics

This result demonstrates that the self-spreading dynamics are controllable by tuning the bilayer-substrate interactions. The above-mentioned electrolyte dependence is an example of this fact. Considering that there are many parameters that alter the bilayer-substrate interaction, a diverse approach can be proposed. For example, Nissen et al. investigated the spreading dynamics on the substrate coated with polymetic materials [48]. They found that insertion of a hydrophilic and inert polymer layer under the self-spreading lipid bilayer strongly attenuated the bilayer-substrate interaction. 

This fact strongly suggests that it is not sufficient to consider only the bilayer-substrate interaction for a comprehensive understanding of the self-spreading dynamics. 

By comparing the structures of DM PC and DMTAP, it is clear that the structure of the head group is different and that DMTAP has a smaller head group. Thus, addition of DMTAP disturbs the formation of a thermodynamically stable bilayer structure. This energy cost reduces the self-spreading driving energy, which could be one of the reasons why the addition of DMTAP led to a decrease in p. 

In addition to the spreading dynamics, the stacking structure of the self-spreading lipid bilayer is also controllable via the NaCl concentration [54, 55]. Further experimental and theoretical investigations regarding the control of self-spreading are required before we will be able to easily control the self-spreading behavior in microfluidic devices. 

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