Development of stimulus responsive soft actuator for ciliary movement

在DMF中合成了以4,4′二氨基偶氮苯（DAA）为骨架的光响应性聚酰胺酸（PAA）和聚酰亚胺（PI）凝胶，并利用扫描显微光散射（SMILS）研究了光照射引起的网目尺寸变化。以4,4′-（六氟异丙基）二苯二酸酐（6FDA）、4,4′-氧化二苯酐（ODPA）、邻苯二酸酐（PMDA）为原料，与三官能团胺1,3,5-三（4-氨基苯基）苯（TAPB）端交联制备了三种不同的酰胺类低聚物。以PAA(OAA（6FDA/DAA)(4/3)-v-TAPB）凝胶为例，smil显示，偶氮苯由纳米级转化为顺式的光异构化导致的网目尺寸变化为2.1 ~ 0.83 nm，与光照射下偶氮苯分子长度的变化相对应。通过在聚合物网络主链中引入刚性芳环，实现了各向同性聚合物凝胶棒的光致宏观弯曲。采用分子动力学（MD）模拟研究了末端连接柔性链和刚性链聚合物网络的形成和结构性质的差异。MD模拟表明，柔性链通过形成微凝胶团簇在大尺度上形成了一个不均匀的网络，这与实验观察结果一致，而刚性链在整个系统体积上迅速形成了一个均匀的网络，而不首先产生微凝胶团簇，另外的区别是它们在局部尺度上产生了相互互穿的网络。采用双光子引发聚合法制备了光响应凝胶针状阵列。在405 nm和532 nm两种不同波长的激光交替激发下，观察了针状阵列的纤毛运动。

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.