US Patent 8931351 Bending sensor

A bending sensor includes a high resistance layer; a low resistance layer having a crack and a lower electrical resistance than the high resistance layer in a state where the crack is closed; an insulating layer between the high and low resistance layers; and a plurality of electrode portions connecting electrically in parallel the high resistance and low resistance layers. In an OFF state where a bend amount is small, the crack is unlikely to open and a combined resistance of electrical resistances of the high resistance layer and the low resistance layer is output as OFF resistance from the plurality of electrode portions. In an ON state where the bend amount is large, the crack is likely to open and at least the electrical resistance of the high resistance layer is output as ON resistance higher than the OFF resistance from the plurality of electrode portions.