Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Macromol Rapid Commun. 2023 Sep;44(18):e2300205. doi: 10.1002/marc.202300205. Epub 2023 Jun 27.
Stimuli-responsive hydrogel actuators are being increasingly used in microtechnology, but typical bilayer hydrogel actuators have significant drawbacks due to weak adhesive interface between the two layers. In this study, thermoresponsive single-layer hydrogel actuators are produced by generating a gradient distribution of cellulose nanocrystals (CNCs) in a poly(N-isopropylacrylamide) (PNIPAAm) hydrogel network by electrophoresis. Tunable bending properties of the composite hydrogels, such as the thermoresponsive bending speed and angle, are realized by varying the electrophoresis time, applied voltage, and CNC concentration. By varying these conditions, the gradient distribution of the CNCs can be optimized, leading to fast bending and large bending angles of the hydrogels. Bending properties are attributed to the gradient distribution of CNCs causing different deswelling rates across the hydrogel network owing to reinforcing effects. Bending ability is also influenced by differences in the CNC dimensions based on the sources of cellulose, which determine the rigidity of the CNC-rich layer of the polymer composite. It is thus shown that thermoresponsive single-layer gradient hydrogels with tunable bending properties can be realized.
刺激响应水凝胶驱动器在微技术中越来越多地被使用，但由于两层之间的粘合界面较弱，典型的双层水凝胶驱动器存在明显的缺点。在这项研究中，通过电泳在聚（N-异丙基丙烯酰胺）（PNIPAAm）水凝胶网络中产生纤维素纳米晶体（CNC）的梯度分布，制备了热响应单层水凝胶驱动器。通过改变电泳时间、施加电压和 CNC 浓度，实现了复合水凝胶的可调弯曲性能，例如热响应弯曲速度和角度。通过改变这些条件，可以优化 CNC 的梯度分布，从而导致水凝胶快速弯曲和大弯曲角度。弯曲性能归因于 CNC 的梯度分布导致水凝胶网络各处不同的溶胀率，这是由于增强作用所致。弯曲能力还受到纤维素来源的 CNC 尺寸差异的影响，这决定了聚合物复合材料中富含 CNC 的层的刚性。因此，证明了可以实现具有可调弯曲性能的热响应单层梯度水凝胶。
