A single-layer valve is provided. The valve comprises a microfluidic pathway at least partially defined by a flexible membrane which is configured to deform when subjected to an actuation torque, and a discontinuity bounded by a first surface. The length of the discontinuity is constant across the full width of the first surface. The valve is configured such that the actuation torque on the membrane is larger in a first direction than a second direction substantially opposite to the first direction.