A method for performing a liftoff operation involves printing a liftoff pattern using low-resolution patterning techniques to form fine feature patterns. The mattress has a supporting surface and a head end. Thickness and boundary extent measurements can be made, for example, of solids, liquids, liquids moving along a horizontal plane, or liquids flowing down a plane. A control circuit can partially disable the alarm signaling function, such as by muting the transducer but continuing to energize the LEDs in response to actuation of the switch.