In this paper, we propose a sensing antenna for detecting leaks in pressurized pipes or industrial storage tanks with a simple passive on-chip network. The chip, fabricated using the integrated passive device (IPD) process, is composed of a section of dual-operational mode synthesized transmission line. The electrical properties of the synthesized line are a function of the material medium surrounding the chip. In air, it is identical to a common transmission line well matched to the system impedance while in a liquid, the high dielectric loading detunes the transmission responses of the chip to block signal flows. This, in turn, prevents the antenna from radiation. The communication link is interdicted, and hence an alert indicating a suspected leak of liquid is released. The design principle and preliminary results are introduced and discussed.