In general, this disclosure is directed to a flexible or stretchable sensor and a method of detecting a substance and/or electromagnetic radiation using said sensor. The sensor comprises a flexible or stretchable substrate, a pair of terminal electrodes disposed on the flexible or stretchable substrate in mutually spaced apart and opposing relation, and a sensing element applied to the flexible or stretchable substrate, between and in electrical contact with the pair of terminal electrodes, wherein the sensing element is responsive to a substance and/or electromagnetic radiation impinging thereon, and wherein when a voltage is applied across the sensor, an electrical signal is generated that is proportional to a resistance value corresponding to a sensing of the substance and/or electromagnetic radiation impinging on the sensing element.