An example sensor includes a flow cell, a detection device, and a controller. The flow cell includes a passivation layer having opposed surfaces and a reaction site at a first of the opposed surfaces. The flow cell also includes a lid operatively connected to the passivation layer to partially define a flow channel between the lid and the reaction site. The detection device is in contact with a second of the opposed surfaces of the passivation layer, and includes an embedded metal layer that is electrically isolated from other detection circuitry of the detection device. The controller is to ground the embedded metal layer.
