Adhesion of bio-inspired microfibre arrays to a rough surface is studied theoretically. The array consists of vertical elastic rods fixed on a rigid backing layer, and the surface is modeled by rigid steps with a normally distributed height. Analytical expressions are obtained for the adhesion forces in both the approach and retraction processes. It is shown that, with the increasing preload, the pull-off force increases at first and then attains a plateau value. The results agree with the previous experiments and are expected helpful in adhesion control of the array in practical applications.
This paper proposes a 3-dimensional coarse grain model of microtubules and treats the tubulin monomer as a sphere of multiple patches, with parameters chosen to yield experimental values of bending and stretching stiffness. The model has demonstrated the ability to produce the bistability of tubulin sheets, elastic deformation near the tip, and cracking and peeling of protofilaments. This model is expected to take into account the structural and mechanical aspects underlying the physical mechanism of polymerization/depolymerization and dynamic instability of microtubules.
Photomechanical response of amorphous polymer films containing azobenzene chromophores in side chains is studied. By invoking the trans-cis isomerization mech- anism, the steady-state deformation of the film induced by uniform illumination of linearly polarized light is obtained analytically. The deformation turns out to be of entropic origin,produced to compensate the entropy decrease due to photo-induced redistribution of azobenzene chromophores normal to the polarization direction. The predicted elongation direction of the film is consistent with previous experimental observations.
