Ji Yuxing, Lin Xiankun, Zhang Hongyue, Wu Yingjie, Li Junbai, He Qiang
Key Laboratory of Microsystems and Microstructures Manufacturing (Ministry of Education), School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Yi kuang jie 2, Harbin, 150080, China.
Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
Angew Chem Int Ed Engl. 2019 Mar 22;58(13):4184-4188. doi: 10.1002/anie.201812860. Epub 2019 Feb 18.
We report a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) brush functionalized Janus Au-Pt bimetallic micromotor capable of modulating the direction of motion with the change of the ambient temperature. The PNIPAM@Au-Pt micromotor moved along the Au-Pt direction with a speed of 8.5 μm s in 1.5 % H O at 25 °C (below the lower critical solution temperature (LCST) of PNIPAM), whereas it changed the direction of motion (i.e., along the Pt-Au direction) and the speed decreased to 2.3 μm s at 35 °C (above LCST). Below LCST, PNIPAM brushes grafted on the Au side were hydrophilic and swelled, which permitted the electron transfer and proton diffusion on the Au side, and thus the motion is regarded as a self-electrophoretic mechanism. However, PNIPAM brushes above LCST became hydrophobic and collapsed, and thus the driving mechanism switched to the self-diffusiophoresis like that of Pt-modified Janus silica motors. These motors could reversibly change the direction of motion with the transition of the hydrophobic and hydrophilic states of the grafted PNIPAM brushes. Such a thermoresponsive polymer brush functionalization method provides a new strategy for engineering the kinematic behavior of phoretically driven micro/nanomotors.
我们报道了一种热响应性聚（N-异丙基丙烯酰胺）（PNIPAM）刷功能化的Janus金-铂双金属微马达，它能够随着环境温度的变化调节运动方向。在25°C（低于PNIPAM的低临界溶液温度（LCST））下，PNIPAM@Au-Pt微马达在1.5%的H₂O中以8.5 μm s的速度沿Au-Pt方向移动，而在35°C（高于LCST）时，它改变了运动方向（即沿Pt-Au方向），速度降至2.3 μm s。在LCST以下，接枝在Au侧的PNIPAM刷是亲水的且膨胀，这允许电子转移和质子在Au侧扩散，因此该运动被视为一种自电泳机制。然而，高于LCST的PNIPAM刷变得疏水并塌陷，因此驱动机制切换为类似于Pt修饰的Janus二氧化硅微马达的自扩散泳。这些微马达可以随着接枝的PNIPAM刷的疏水和亲水状态的转变而可逆地改变运动方向。这种热响应性聚合物刷功能化方法为设计电泳驱动的微/纳米马达的运动行为提供了一种新策略。
