Effects of micro- and nano-scale surface geometry on behaviors of live cells and liquid droplets

C2C12;cell alignment;droplet;superhydrophobic;optogenetics;MCF10a;Buckling;Surface waviness

Grigola, Michael ; Hsia ; K. Jimmy

关键词: C2C12;    cell alignment;    droplet;    superhydrophobic;    optogenetics;    MCF10a;    Buckling;    Surface waviness;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/49502/Michael_Grigola.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

As the scale of the surface texture responsible for superhydrophobicity becomes similar to the size of adroplet, simple models based on homogeneity assumptions begin to break down. In order to betterunderstand these discrete phenomena, we first create a unique model with the finite element software,Surface Evolver, which simulates a droplet atop the individual features that comprise asuperhydrophobic surface. We observe that the well-known Cassie-Baxter and spherical cap modelsgive poor estimates of characteristics such as contact angle and wet area and also fail to capture thecomplex liquid surface geometry when features have discrete size. Further exploring this theme, weconsider the influence of gravity on these theoretical models using analytical and simulation results, andwe find that the impact of gravity on droplet shape becomes non-negligible as surfaces become veryhydrophobic. Motion is also significantly affected by discrete features, for example increasedhydrophobicity may actually hinder droplet motility due to pinning. In light of this, we analyze datacollected with a novel method of measuring forces in moving droplets to better understand thedynamics of pinning. The results and methodology developed here will help other researchers betterunderstand the relevant mechanics in micro-scale droplets.In a different setting, surface geometry also affects biological cells by altering their mechanicalenvironment. In the case of cell mechanics we generally lack even a flawed model for describing theobserved behavior, so we seek to identify parameters that might simplify these cellular systems. Onemethod that allows us to investigate the effects of mechanics on cells is to expose the cells to uniform,periodic patterns. We first describe a unique procedure for generating approximately sinusoidalpatterns at multiple length scales using thin-film buckling. These patterns are applied to study cells, firstwith muscle cells at the nano- to micro-scale where the patterns help identify a trend of musclealignment as a function of surface characteristics. In the process we discover that cell-cell interactionalso plays a role in the alignment. Next we investigate the effects of geometry on epithelial cells wherethe wavy patterns are used to ascertain the cause of unexpected ductal formations in a hydrogelculture. The cause is apparently mechanical and a result of variation in stiffness due to the underlyinggeometry. A final section also illustrates some of the techniques that were developed and used toinvestigate these phenomena, and which may be used by other researchers to further study thesetopics. These studies help better our understanding of mechanics at the micro- and nano-scale, whilethe methods used herein may be applied to a number of similar systems.