Patent ID: 7038470

Claim:
A capacitive element comprising: (a) a substrate having a top surface and a bottom surface; (b) a rigid frame having a top surface and a bottom surface wherein the bottom surface of the rigid frame is adhered to the top surface of the substrate; (c) a first metal capacitive plate having a top surface, a bottom surface, at least one side surface, and an electrical connection to a terminal wherein the bottom surface of the first metal capacitive plate is affixed to a first portion of the top surface of the rigid frame; (d) a flexible frame having at least one opening that passes through the flexible frame, a top surface having a depression, and a bottom surface wherein a portion of the top surface of the flexible frame surrounding the depression is affixed to a second portion of the top surface of the rigid frame so as to form a cavity together with the rigid frame and so that: (i) the at least one opening exposes a portion of the cavity to the environment, and (ii) the first metal capacitive plate is disposed within the cavity; (e) a second metal capacitive plate having a top surface, a bottom surface, at least one side surface, and an electrical connection to a terminal wherein the bottom surface of the second metal capacitive plate is affixed to a portion of the depression so that the second metal capacitive plate is disposed: (i) within the cavity, and (ii) parallel to the first metal capacitive plate and symmetrically about a plane within the cavity to the first capacitive plate; (f) an active material arranged within the cavity so that the active material: (i) fills the cavity, and (ii) receives environmental parameter signals passing through the at least one opening; (g) a first insulating layer applied to the top and side surfaces of the first metal capacitive plate so as to insulate the first metal capacitive plate from the active material; and (h) a second insulating layer applied to the top and side surfaces of the second metal capacitive plate so as to insulate the second metal capacitive plate from the active material, wherein the total open area of the at least one opening is sufficiently large enough for rapid ingress or egress of environmental parameter signals and each of the at least one openings is sufficiently small enough to retain the active material within the cavity.