Soft actively contractile cylinders and spheres*

In the last years, contractile gels have been the subject of intense research activity. Active gel microtubules have been produced to investigate how the dynamics of diffusion can be enhanced when gel activity is driven by molecular motors (Phil.Trans.R.Soc. A 372, 2014). Likewise, buckling shapes of thin sheets made of active polymers have been presented and discussed (Nature Communications 9, 2018). On a different side, microfluidic applications based on polymer microtubules have been investigated (Lab on a Chip 18, 2018).
In all those examples, active contraction of the gels as well as solvent release and flows contribute to the dynamics of the active gel structures and determine the smoothly or suddenly change of the original geometric shapes. Our mathematical model can describe some of the key features of these dynamics. We view active contraction as a change in the material metric of the structures, and describe it within a theory of stress-diffusion with remodeling of the polymeric network. The results of the model will be compared and contrasted with the observations of actual experiments on microtubules and microspheres.