Embodiments include a method for securing a membrane material to a gate of a molecular receptor-based chemical field-effect transistor (CHEMFET). The method can include casting a membrane material onto an exposed region of the gate, curing the membrane material, placing the CHEMFET into a mold, inserting a single application of impervious electrically insulative resin into the mold, and securing edges of the membrane material by the single application of the impervious electrically insulative resin, thereby physically preventing lifting off of the membrane material from the gate. Embodiments include a sensor module. The sensor module can include a CHEMFET, an amplifier circuit, one or more sensor pins for contacting field ground soil, a data logger, and a wireless transceiver, among other components.