Wenxin Fan,Jincai Yin,Chenglin Yi,Yanzhi Xia,Zhihong Nie,Kunyan Sui
The design of materials that can mimic encoded shape evolution in nature is important but challenging. Here we present a simple yet versatile strategy for programming the sequential deformation of hydrogel sheets to acquire desired actuation motions and geometric shapes. The method relies on the dual-gradient structure-enabled snapping deformation of hydrogels through the accumulation and burst release of elastic energy, as well as the patterning of the prestored energy in gels. Pretreating distinct regions of the hydrogel sheets with different durations of the same stimulus (or with different stimuli) allows for locally prestoring chemical energy that can be converted to temporospatially patterned elastic energy and abruptly released to drive the successive snapping of different regions of hydrogels in predefined onset sequences. The sequence of energy release (i.e., the sequence of snapping deformation) of the local regions for hydrogels can be reprogrammed by different local prestimulation methods, which allows one gel to deform into various defined geometric configurations. The general mathematic criteria are developed to predict the energy release and snapping of the hydrogels. This work can provide guidance for the design of new-generation actuators and soft robotics.
Ma Suqian,Jiang Zeyu,Wang Meng,Zhang Lan,Liang Yunhong,Zhang Zhihui,Ren Lei,Ren Luquan
Abstract Shape memory polymers (SMPs) are a promising class of materials for biomedical applications due to their favorable mechanical properties, fast response, and good biocompatibility. However, it is difficult to achieve controllable sequential shape change for most SMPs due to their high deformation temperature and the simplex deformation process. Herein, shape memory composites based on polylactic acid (PLA) matrix and semi-crystalline linear polymer polycaprolactone (PCL) are fabricated using 4D printing technology. Compared with pure PLA, with the rise of PCL content, the 4D-printed PLA/PCL composites show decreased glass transition temperature ( T g ) from 67.2 to 55.2 °C. Through the precise control of the deformation condition, controllable sequential deformation with an outstanding shape memory effect can be achieved for the PLA/PCL shape memory composites. The response time of shape recovery is less than 1.2 s, and the shape fixation/recovery rates are above 92%. In order to simulate sequential petal opening and sequential drug releasing effects, a double-layer bionic flower and a drug release device, respectively, are presented by assembling PLA/PCL samples with different PLA/PCL ratios. The results indicate the potential applications of 4D-printed PLA/PCL composites in the field of bio-inspired robotics and biomedical devices. Graphic abstract
危险品化学品经营许可证（带存储）