4D Printed Shape-Memory Elastomer for Thermally Programmable Soft Actuators

Polymeric shape-memory elastomers can recover to a permeantshapefrom any programmed deformation under external stimuli. They are mostlycross-linked polymeric materials and can be shaped by three-dimensional(3D) printing. However, 3D printed shape-memory polymers so far onlyexhibit elasticity above their transition temperature, which resultsin their programmed shape being inelastic or brittle at lower temperatures.To date, 3D printed shape-memory elastomers with elasticity both belowand above their transition temperature remain an elusive goal, whichlimits the application of shape-memory materials as elastic materialsat low temperatures. In this paper, we printed, for the first time,a custom-developed shape-memory elastomer based on polyethylene glycolusing digital light processing, which possesses elasticity and stretchabilityin a wide temperature range, below and above the transition temperature.Young's modulus in these two states can vary significantly,with a difference of up to 2 orders of magnitude. This marked differencein Young's modulus imparts excellent shape-memory propertiesto the material. The difference in Young's modulus at differenttemperatures allows for the programming of the pneumatic actuatorsby heating and softening specific areas. Consequently, a single actuatorcan exhibit distinct movement modes based on the programming processit undergoes.

Automated summary

This research presents the first demonstration of digital light processing-printed shape-memory elastomers based on polyethylene glycol, which exhibit elasticity and stretchability in a wide temperature range below and above the transition temperature. The significant difference in Young's modulus at different temperatures allows for programming of the pneumatic actuators by heating and softening specific areas.