Pattern-driven 4D printing

Sensors and Actuators A: Physical 2018 Volume 274, Pages 231-243

Self-bending actuators have time and cost reduction benefits for applications like self-assembly and self-deployable structures. Three-dimensional (3D) printing is a promising rapid and accurate manufacturing method for controlling spatial self-bending actuation in custom-designed soft structures. This paper studies the features merely imparted by 3D printing fabrication in control of self-folding actuators. It is shown that 3D printing control parameters such as different spatial patterns of hinges affect the response time and bending angle of the actuator. A polystyrene (PS) pane as a representative of thermo-responsive shape memory polymers is used as the main material for being remotely stimulated via light emission while the actuation hinges are made of printed chitosan hydrogel ink. The hinges function as a heat source to absorb a wide range of light, particularly the infrared light, convert light energy to thermal energy and cause the underlying printed area to heat up faster than the unprinted area leading to actuation due to thermal stress gradients. A parametric study of physical properties of polymer pane incorporating 3D printed patterns is conducted. Also, experimental tests carried out to validate the proposed parametric model. The proposed model predicts the final shape of the actuator with excellent qualitative agreement with experimental studies. The validated results can provide guidelines for the design of functional, self-bending actuators using 3D printing.