Light-based 3D printing of hydrogels with high-resolution channels

Hydrogels are soft, water-based gels with widespread applications in personal care products, medicine and biomedical engineering. Many applications require structuring the hydrogel into complex three-dimensional (3D) shapes. For these applications, light-based 3D printing methods offer exquisite control over material structure. However, the use of these methods for structuring hydrogels is underdeveloped. In particular, the ability to print hydrogel objects containing internal voids and channels is limited by the lack of well-characterized formulations that strongly attenuate light and the lack of a theoretical framework for predicting and mitigating channel occlusion. Here we present a combined experimental and theoretical approach for creating well-defined channels with any orientation in hydrogels using light-based 3D printing. This is achieved by the incorporation of photoblocker and the optimization of print conditions to ensure layer-layer adhesion while minimizing channel occlusion. To demonstrate the value of this approach we print hydrogels containing individual spiral channels with centimeter-scale length and submillimeter-scale cross-section. While the channels presented here are relatively simple, this same approach could be used to achieve more complex channel designs mimicking, for example, the complex vasculature of living organisms. The low cytotoxicity of the gel makes the formulation a promising candidate for biological applications.