High-Resolution 3D Printing of Stretchable Hydrogel Structures Using Optical Projection Lithography

Abstract

Double-network (DN) hydrogels, with their unique combination of mechanical strength and toughness, have emerged as promising materials for soft robotics and tissue engineering. In the past decade, significant effort has been devoted to synthesizing DN hydrogels with high stretchability and toughness; however, shaping the DN hydrogels into complex and often necessary user-defined two-dimensional (2D) and three-dimensional (3D) geometries remains a fabrication challenge. Here, we report a new fabrication method based on optical projection lithography to print DN hydrogels into customizable 2D and 3D structures within minutes. DN hydrogels were printed by first photo-crosslinking a single network structure via spatially modulated light patterns followed by immersing the printed structure in a calcium bath to induce ionic cross-linking. Results show that DN structures made by this method can stretch four times their original lengths. We show that strain and the elastic modulus of printed structures can be tuned based on the hydrogel composition, cross-linker and photoinitiator concentrations, and laser light intensity. To our knowledge, this is the first report demonstrating quick lithography and high-resolution printing of DN (covalent and ionic) hydrogels within minutes. The ability to shape tough and stretchable DN hydrogels in complex structures will be potentially useful in a broad range of applications.

Oxygen-Permeable Films for Continuous Additive, Subtractive, and Hybrid Additive/Subtractive Manufacturing

“…Due to the presence of the dead zone, the photocrosslinked part is continuously drawn out of the sample holder and the advancing part creates suction forces that constantly draw liquid resin into the fabrication area. 17 This facilities continuous and fast printing of the structures, 17,18,24 unlike the traditional stereolithography approach that is a sequential and slow process of printing. 25,26 For instance, in this work, a printing speed of 1.44 m/h was obtained using PDMS-1, PDMS-2, and Teflon films, and a printing speed of 0.7 m/h was achieved with PU films.…”

“…However, the speed of fabrication is limited to a few millimeters per hour in the case of conventional stereolithography. 24 The ablation z-range for subtractive mode of printing is also fundamental to the HLP process. 18 Within the ablation z-range, material can be reliably removed using laser-based ablation and is important to determine the exact location of laser focus during the subtractive mode of fabrication.…”

Crosslinking Trends in Multicomponent Hydrogels for Biomedical Applications

“…is well reported and the latest technologies (e.g., optical projection lithography, bioprinting, microfluidics, and biopatterning) provide the methods to design scaffold with intricate structures for various biomedical applications. [71][72][73][74] However, the construction of functional tissues, still remains a challenge, since it relies on many parameters, which include polymer structure, cell-biomaterial interactions, encapsulated materials, etc. Thus, the designed material must offer properties (i.e., good mechanical strength, stability, and biocompatibility) that lead to cellular function in a natural manner.…”

Cryptographic Strain‐Dependent Light Pattern Generators

“…Controlling the spatial profile of light beams is critically important in various scientific and technological fields, including high‐resolution microscopy, [ 1 ] endoscopy, [ 2 ] lithography and additive manufacturing, [ 3 ] optical manipulation of micro‐objects, [ 4 ] wireless communication, [ 5 ] and computation. [ 6 ] Various methods have been reported to this aim, mostly based on diffractive elements and digital holography, which exploit arrays of micromirrors, [ 7 ] liquid crystal‐based modulators, [ 8 ] or metasurfaces.…”