A sensing device includes a robot hand, an electrode and a triboelectric sensing layer. The robot hand includes at least one robot finger. The electrode is disposed on a surface of the at least one robot finger. The triboelectric sensing layer is disposed on the electrode, and has a plurality of micro structures. Each of the micro structures includes tellurium. The triboelectric sensing layer has a first electron transmission ability and is for contacting a target object. Tellurium of at least part of the micro structures undergoes a chemical reaction with mercury ions in the target object and forms mercury telluride such that the triboelectric sensing layer after contacting with the target object has a second electron transmission ability. The second electron transmission ability is different from the first electron transmission ability such that an output voltage of the electrode is changed. Therefore, the sensing device is able to measure mercury ion concentration in the target object. |