Peng Xin, Liu Tianqi, Jiao Chen, Wu Yuqing, Chen Nan, Wang Huiliang
Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China.
J Mater Chem B. 2017 Oct 21;5(39):7997-8003. doi: 10.1039/c7tb02119d. Epub 2017 Oct 2.
Stimuli-responsive hydrogels, with programmable shape deformations upon external stimuli, have promising applications in diverse fields. Complex shape deformation through precise remote control of the direction, position and degree of deformation is critical for practical applications. Herein, we describe a novel and facile method that enables remote and instant programming of the deformation direction, position and degree of homogeneous poly(N-isopropylacrylamide)/graphene oxide (PNIPAM/GO) nanocomposite hydrogels through local near infrared (NIR) laser irradiation. Under NIR irradiation, GO nanosheets absorb NIR light, which transforms into heat and induces the phase transition of PNIPAM. Due to the slow heat transfer of the hydrogels, the irradiated part of the PNIPAM/GO hydrogels shrinks more than the un-irradiated part, leading to the folding or bending of the gels toward the irradiated part. The deformation degree of the hydrogels can be adjusted by changing the composition (e.g., GO concentration) or the thickness of the hydrogels and the irradiation parameters, including power density of NIR laser and irradiation time. Impressively, by simply programming the local irradiation on different parts of hydrogel strips, sheets and gel samples with other shapes, the hydrogel samples can undergo complex shape deformations from 1D to 2D and 2D to 3D, and imitate the postures of a human and the closing of the leaves of mimosa.
刺激响应性水凝胶在外部刺激下具有可编程的形状变形，在多个领域有着广阔的应用前景。通过精确远程控制变形方向、位置和程度来实现复杂形状变形对于实际应用至关重要。在此，我们描述了一种新颖且简便的方法，该方法能够通过局部近红外（NIR）激光照射对均匀的聚（N-异丙基丙烯酰胺）/氧化石墨烯（PNIPAM/GO）纳米复合水凝胶的变形方向、位置和程度进行远程即时编程。在近红外照射下，氧化石墨烯纳米片吸收近红外光，其转化为热量并诱导聚N-异丙基丙烯酰胺的相变。由于水凝胶的热传递较慢，PNIPAM/GO水凝胶的照射部分比未照射部分收缩得更多，导致凝胶朝着照射部分折叠或弯曲。水凝胶的变形程度可以通过改变组成（例如氧化石墨烯浓度）、水凝胶的厚度以及照射参数（包括近红外激光的功率密度和照射时间）来调节。令人印象深刻的是，通过简单地对水凝胶条、片以及其他形状的凝胶样品的不同部位进行局部照射编程，水凝胶样品可以经历从一维到二维以及从二维到三维的复杂形状变形，并模仿人类姿势和含羞草叶片的闭合。
