Projection-suspended stereolithography 3D printing for low-loss optical hydrogel fiber fabrication

Hydrogel fiber (HF) has shown great potential for delivering light and sensing in vivo. However, HFs commonly suffer from high optical attenuation, which significantly affects their light-guiding efficiency and sensing performance. Here, we demonstrate a projection-suspended stereolithography (PSS) 3D printing method for fabricating low-loss HF. Axially continuous and uniform HF is produced via a light-curing area that floats on the precursor solution. Additionally, PSS improves the guiding efficiency of the HF by simultaneously regulating the fiber diameter, core-cladding structure, and refractive index (RI). We obtained a loss {less than or equal to} 0.15 dB/cm, which is better than that reported by previous studies. We also demonstrate that the fabricated HF provides light delivery and sensing capability in deep tissues, which will benefit the development of biomedicine and optogenetics. The PSS method heralds a novel fabrication for advanced waveguides.