4D Printing in Micro/Nano Scale

Abstract

3D printing of flexible and active shapes, commonly known as 4D printing, has revolutionized the world of additive manufacturing by introducing the concept of self-transforming structures. The added dimension in 4D printing signifies the ability of additively manufactured objects to change their characteristics, such as shape, over time in response to external stimuli. Although significant advancements have been achieved in the creation and production of printing materials on a large scale, the field of 4D printing at the micro-/nano- scale is still in its early stages due to several difficulties in constructing structures with micro/nano-sized features. This book chapter delves into the emerging field of micro/nano scale 4D printing, highlighting the cutting-edge technologies being developed and exploring their potential applications. The chapter begins by introducing the concept of 4D printing and its significance in advanced manufacturing. It provides an overview of the transition from 3D printing to 4D printing and the potential impact of this evolution. The main focus of the chapter is on presenting various micro/nano scale 4D printing technologies. These techniques include liquid crystal elastomerbased miniaturization printing, two-photon polymerization, micro stereolithography, laser transfer micro additive manufacturing, ink-based micro additive manufacturing, hydrogel-based miniaturization printing, micro laser sintering, and beam deposition. Each of these technologies is discussed in detail, highlighting their unique capabilities and limitations. The chapter presents several compelling case studies that showcase the practical applications of micro/nano scale 4D printing. These examples illustrate how these innovative technologies can be leveraged in diverse fields such as micro-robotics, optics, and biomedicine. The utilization of 4D microprinting has the capacity to demonstrate exceptional shape memory characteristics and activation at minimal stimulation levels; hence, creating new opportunities for the advancement of practical and adaptable micro/nano devices.