Figure 4.

Mechanical properties of the polymerized hydrogel + UCNPs using 976 and 405 nm irradiation under different tissue thicknesses. Once a precursor of the hydrogel (containing 15 wt % polymer contents with 15 mg/mL UCNPs and 0.2 wt % LAP in a mold) was placed under the tissue; a laser beam of 976 nm wavelength, 19 μm of diameter, and 0.7 W power was used to irradiate the sample from the top for 10 min. Photopolymerization using 405 nm light was conducted on a conventional setup with a uniform illumination using a lamp (see the Methods Section).