A cage can include a thermal plate positioned so as to be aligned with a bottom of a channel. A reference pressure cavity of the sensor is evacuated through an evacuation opening located behind a plate portion of the sensor electrode having a non-planar surface for supporting the diaphragm during an overpressure event. The system includes at least one vessel containing at least one wetting agent or surfactant. The separate safety pocket protects the smart phone from scratches from coins and keys. Methods of preparing such foams and articles comprising such foams are also described. A correction matrix is developed from the partial description of the reverse channel and a description of the forward channel.