4.7 Characterization
The hydrogels’ mechanical properties were measured using a UTM2203 universal testing machine (Technology Stock Co., Ltd., Shenzhen, China) at a stretching rate of 50 mm min−1. A CEL-SSOO xenon lamp (Au-light Co., Ltd., Beijing, China), simulating solar irradiation, served as the light source. Voltage changes were recorded with a Keithley 6514 system electrometer (Keithley Co., Ltd., Johnston City, Ohio, USA). The electrical conductivity of the hydrogels was measured using a Quantum Design PPMS-9 measurement system (Ceshigo, Chengdu, China). Surface temperature of the hydrogels was measured with a UT325 thermometer (Alibaba). UV-Vis absorption spectra were recorded from 200 to 800 nm using a TU-1901 UV-Vis double-beam spectrophotometer (Persee General Instrument Co., Ltd., Beijing, China).