▎ 摘　　要

Intrinsic bilayer graphene is a gapless semimetal. Under the application of a bias field it becomes a semiconductor with a direct band gap that is proportional to the applied field. Under a layer-asymmetric strain (where the upper layer undergoes compression and the lower layer tension or vice versa) we find that the band gap of a biased bilayer graphene ribbon becomes indirect and, for higher strains, becomes negative, returning the material to its original semimetal state. As a result, the conductivity of the ribbon increases and can be almost an order of magnitude larger than that of the intrinsic unbiased material-a change that can be induced with a strain of only approximate to 2-3%. The conductivity is proportional to the applied strain and the magnitude of the effect is tunable with the bias field. Such layer-asymmetric strains can be achieved by bending, with forces on the order of approximate to 1 nN, resulting in a layer-asymmetric strain of approximate to 1%. This electromechanical effect has a wide potential for application in the areas of nanoforce microscopy and pressure sensing on the atomic scale.