A Review on 3D Printed Smart Devices for 4D Printing

Multi-material 3D printing with electrically functional materials including conducting, sensing, insulating and semiconducting materials has led to the development of smart devices such as 3D structural electronics, sensors, batteries, etc. Electronically smart devices are a hot issue in 3D printing because they can certainly benefit from 3D printing technology, providing high design flexibility and customized functions. Shape-changing materials (e.g. shape memory polymers) incorporated in 3D printing have given birth to 4D printing, where 3D printed structures change in their shapes by external stimuli (temperature, light, water, etc.). The motivation of this review paper is to discuss mutual benefits from both 3D printed smart devices and 4D printed features, which can be built in a single body. It is expected that the combination of 3D printed smart devices and 4D printing would contribute to the development of high performance, adaptability to the environment and programmable 3D smart devices, which have not yet existed. This paper has reviewed the background of 3D printing, smart device fabrication using 3D printing, development into 4D printing, and future applications of 4D printing.