posted on 2020-03-19, 17:36authored byLuquan Ren, Bingqian Li, Yulin He, Zhengyi Song, Xueli Zhou, Qingping Liu, Lei Ren
Currently,
four-dimensional (4D) printing programming methods are
mainly structure-based, which usually requires more than one material
to endow products with site-specific attributes. Here, we propose
a new 4D printing programming approach that enables site-specific
shape-morphing behaviors in a single material by regulating the printing
parameters. Specifically, a direct ink writing three-dimensional (3D)
printer with the ability to change printing parameters (e.g., deposition
speed) on the fly is reported. By site-specifically adjusting print
speed and print path to control the local nematic arrangements of
printed liquid crystal elastomers (LCEs), the shape-morphing behaviors
of the LCEs can be successfully programmed. In this way, locally programmed
popping-up, self-assembling, and oscillating behaviors can be designed
by varying the print speed in specific regions. Snake-like curling
is realized by uniformly boosting the print speed in a single line.
Furthermore, two theories and an ultrasound image diagnostic apparatus
are employed to reveal the mechanism behind this behavior. This work
provides a feasible way to realize the gradient transition of material
properties through a single material. It broadens the design space
and pushes the envelope of 4D printing, which is expected to be helpful
in the fabrication of soft robotics and flexible electronics.