Methods and devices for determining sensing device usability, e.g., for point of care immunoassay devices. In one embodiment, the invention is to a method of determining device usability, comprising the steps of providing a device comprising a first electrical pad; a second electrical pad; and a continuous polymer layer contacting at least a portion of the first and second electrical pads; applying a potential across the first and second electrical pads; measuring an electrical property associated with the continuous polymer layer; and determining whether the measured electrical property associated with the continuous polymer layer has exceeded a threshold level associated with the device usability.