4D Printing of a Light-Driven Soft Actuator with Programmed Printing Density

Abstract

There is a growing interest in the concept of four-dimensional (4D) printing that combines a three-dimensional (3D) manufacturing process with dynamic modulation for bioinspired soft materials exhibiting more complex functionality. However, conventional approaches have drawbacks of low resolution, control of internal micro/nanostructure, and creation of fast, complex actuation due to a lack of high-resolution fabrication technology and suitable photoresist for soft materials. Here, we report an approach of 4D printing that develops a bioinspired soft actuator with a defined 3D geometry and programmed printing density. Multiphoton lithography (MPL) allows for controlling printing density in gels at pixel-by-pixel with a resolution of a few hundreds of nanometers, which tune swelling behaviors of gels in response to external stimuli. We printed a 3D soft actuator composed of thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) and gold nanorods (AuNRs). To improve the resolution of printing, we synthesized a functional, thermoresponsive macrocrosslinker. Through plasmonic heating by AuNRs, nanocomposite-based soft actuators undergo nonequilibrium, programmed, and fast actuation. Light-mediated manufacture and manipulation (MPL and photothermal effect) offer the feasibility of 4D printing toward adaptive bioinspired soft materials.

Structural multi-colour invisible inks with submicron 4D printing of shape memory polymers

“…Printed features as small as ~10 nm can be achieved under specific conditions 43 . Due to the high resolution it provides, TPL has been used to print different stimuli responsive materials such as hydrogels 6 , 44 , liquid crystal elastomers 41 , 45 , magnetic nanoparticles embedded resists 46 , 47 , silicon functionalized monomers 48 and other examples printing 49 . Recently, hydrogel photoresists have been used for tunable photonic devices.…”

4D Printing Pre-Strained Structures for Fast Thermal Actuation

“…Ge et al (2013) fabricate thermal responsive 4D printed structure by printing shape memory polymer fibers in an elastomeric matrix. Although widely used in 4D printing, thermal responsive structures (Le Duigou et al, 2019;Nishiguchi et al, 2020) have a major problem in slow actuation resulting from the low heat conduction rate of the structures, especially the cooling rate.…”

In Situ 3D-Printing using a Bio-ink of Protein–photosensitizer Conjugates for Single-cell Manipulation

“…Tuning hatching/slicing distance can change the density of printing networks in hydrogels and the stiffness of hydrogels. 27 The accurate control of the cellular microenvironment, especially in the presence of cells, would contribute to understanding cell functions. For further advances, the development of advanced technology that can modulate matrix stiffness, 28 , 29 topologically guide the migration, 30 , 31 pattern biomolecules, 32 , 33 combine with cell encapsulation in bioprinting 34 would be a key challenge to direct cell fate.…”