A temperature sensor is described, which includes a sensor gel having a polymer, water and ions, and a first and a second electrode separated from each other by the sensor gel. The present disclosure further relates to a system which has a temperature sensor, a voltage source or electric current source, and a measurement device for detecting voltage or electric current. The present disclosure further relates to a bolometer and a temperature sensor array. A method for temperature detection is also described, wherein a temperature sensor is provided, a voltage or an electric current between the first electrode and the second electrode of the temperature sensor is provided, an electric current or a voltage between the first electrode and the second electrode is measured, and a temperature is determined from the measured electric current or voltage.