Controllable mass production of monodisperse droplets plays a key role in numerous fields ranging from scientific research to industrial application. Microfluidic ladder networks show great power in mass production of...

Transcatheter arterial radioembolization (TARE) is of great significance for the treatment of advanced hepatocellular carcinoma (HCC). However, the existing radioembolic microspheres still have problems such as non‐degradability, non‐uniform size, and inability to directly monitor in vivo, which hinders the development of TARE. In this paper, a novel radioembolic agent, 131I‐labeled methacrylated gelatin microspheres (131I‐GMs), is prepared for the treatment of HCC. Water‐in‐oil (W/O) emulsion templates are prepared by a simple one‐step microfluidic method to obtain methacrylated gelatin microspheres (GMs) after UV irradiation. A series of GMs with uniform and controllable size is obtained by adjusting the flow rate of each fluid. Both air‐dried and freeze‐dried GMs can quickly restore their original shape and size, and still have good monodispersity, elasticity, and biocompatibility. The radiolabeling experiments show that 131I can efficiently bind to GMs by chloramine‐T method, and the obtained 131I‐GMs have good radioactive stability in vitro. The results of in vivo TARE treatment in rats show that 131I‐GMs can be well retained in the hepatic artery and have a good inhibitory effect on the progression of liver cancer, showing the potential for the treatment of HCC.