After printing the slides containing prepolymerization mixture were transferred into a petri dish containing 2 mL PBS in the bottom, covered with a quartz glass plate and irradiated for 30 min with a UV LED (Opsytec, Ettlingen, Germany) at 5.41 mW cm -2 . After the polymerization Slides were taken out of the dish and submerged in a solution of Rhodamine 6G (10 mg L -1 ) in PBS for 16 h.