Development of stimulus responsive soft actuator for ciliary movement

点击翻译按钮获取中文摘要

Photoresponsive poly(amide acid) (PAA) and polyimide (PI) gels consisting of 4, 4' diamino azobenzene (DAA) in backbone were synthesized in DMF, and mesh-size changes induced by photoirradiation were investigated by using scanning microscopic light scattering (SMILS). Three different kinds of amide acid oligomers derived from 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4'-oxydiphthalic anhydride (ODPA), pyromellitic dianhydride (PMDA), were end-crosslinked with trifunctional amine, 1,3,5-tris(4-aminophenyl)benzene (TAPB). In the case of PAA(OAA(6FDA/DAA)(4/3)-v-TAPB) gels, SMILS has revealed that mesh size change due to the photoisomerization of azobenzene from nanoscopically trans-form to cis-form amounts to be from 2.1 to 0.83 nm, and corresponds to the change in molecular length of azobenzene upon photo-irradiation. Photo-induced macroscopic bending of isotropic polymer gel rods was realized by introducing rigid aromatic rings into main chains of the polymer network.The differences in formation and structural properties of polymer networks consisting of end-linked flexible or rigid chains were studied by molecular dynamics (MD) simulation. MD simulations showed that the flexible chains created an inhomogeneous network on a large scale via microgel cluster formation, in agreement with experimental observations, whereas the rigid chains rapidly created a homogeneous network in the entire system volume without first generating microgel clusters, with the additional difference that they gave rise to mutually interpenetrating networks at the local scale.Needle array of photoresponsive gel were prepared by use of nano holes template fabricated by two-photon initiated polymerization. Ciliary movement of needle like array were observed by alternating laser excitation at two different wavelength, 405 nm and 532 nm.