a first body and a second body;

a pivot, pivotally connected between the first body and the second body, wherein the first body and the second body is configured to rotate relatively to each other through the pivot; and

a key module comprises a bendable substrate and a sensor embedded in the bendable substrate, wherein the bendable substrate is covered a part of the first body and a part of the second body and covers an outer side of the pivot, and the sensor generates a sensing signal in response to a press of a user upon the bendable substrate,

the first body, the second body, the outer side of the pivot and the key module together enclose a space,

wherein the bendable substrate comprises a plurality of flexible layers and a plurality of rigid reinforcements respectively sandwiched between the plurality of flexible layers,

wherein the plurality of flexible layers are connected between the first body and the second body, and the plurality of rigid reinforcements are arranged spaced apart from each other such that the plurality of flexible layers are suitable for bending between the plurality of rigid reinforcements.