Abstract
Abstract Three-dimensional (3D) printing enables the fabrication of complex, highly customizable structures, which are difficult to fabricate using conventional fabrication methods. Recently, the concept of four-dimensional (4D) printing has emerged, which adds active and responsive functions to 3D-printed structures. Deployable or adaptive structures with desired structural and functional changes can be fabricated using 4D printing; thus, 4D printing can be applied to actuators, soft robots, sensors, medical devices, and active and reconfigurable photonic devices. The shape of 3D-printed structures can be transformed in response to external stimuli, such as heat, light, electric and magnetic fields, and humidity. Light has unique advantages as a stimulus for active devices because it can remotely and selectively induce structural changes. There have been studies on the light activation of nanomaterial composites, but they were limited to rather simple planar structures. Recently, the light activation of 3D-printed complex structures has attracted increasing attention. However, there has been no comprehensive review of this emerging topic yet. In this paper, we present a comprehensive review of the light activation of 3D-printed structures. First, we introduce representative smart materials and general shape-changing mechanisms in 4D printing. Then, we focus on the design and recent demonstration of remote light activation, particularly detailing photothermal activations based on nanomaterial composites. We explain the light activation of 3D-printed structures from the millimeter to sub-micrometer scale.
Highlights
Three-dimensional (3D) printing is a bottom-up fabrication method used for building arbitrary 3D objects layerby-layer with a high level of customization [1,2,3]
We present a comprehensive review of the light activation of 3D-printed structures
We focus on the design and recent demonstration of remote light activation, detailing photothermal activations based on nanomaterial composites
Summary
Three-dimensional (3D) printing is a bottom-up fabrication method used for building arbitrary 3D objects layerby-layer with a high level of customization [1,2,3]. We discuss photochemical and photothermal activations, detailing photothermal activations based on nanomaterial composites We describe how such light-activation mechanisms were used in the recent demonstrations of 3D-printed, active structures from the millimeter scale to the sub-micrometer scale (Sections 4.3–4.5). While our review aims to discuss recent progresses in 3D-printed structures, we included discussions on general photochemical (Section 4.1.1) and photothermal (Section 4.2) activations based on traditional fabrication methods (such as hot pressing and molding) [31, 32]. These sections provide general backgrounds for the following sections (Sections 4.1.2 and 4.3–4.5) on the light activation of 3D-printed structures
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