The active development of global industry leads to increasing pollution of the environment with heavy metals, and therefore control of their content in water is relevant. The use of modern portable devices al-lows detection in the field. An important issue is to increase the sensitivity and selectivity of the sensors used. Currently, polyethylene terephthalate track-etched membranes are widely used for flexible electro-chemical sensors for the analysis of metal cations in aqueous solutions. Aim of the work is to develop a method for the formation and reserch the physical and mechanical properties of sensitive Langmuir - Blodgett films based on perfluorooctadecanoic acid for electrochemical sensors for the analysis of metal cations in aqueous solutions. Flexible sensors for the analysis of lead cations in water have been developed based on polyethylene terephthalate track-etched membranes modified by the Langmuir - Blodgett technology by a monolayer of perfluorooctadecanoic acid with deposition of xylenol orange and dimethylglyoxime layers. The structure and local mechanical properties of modified membrane surfaces were studied using atomic force microsco-py. Based on changes in the values of nanoroughness and mechanical properties, the presence of a modifier on the surface of the substrates is shown. The change in wettability of track-etched membranes was assessed by sessile drop method. It has been established that modification of perfluorooctadecanoic acid with Langmuir-Blodgett films increases the contact angle of the membrane surface from 50º to 62.9º and 70.0º of polyethylene terephthalate track-etched membranes with pore diameters 50 and 100 nm consequently. For samples modified with xylenol orange values of contact angle are changed from 56.6º and 73.8º of pol-yethylene terephthalate track-etched membranes with pore diameters 50 and 100 nm consequently. Based on voltammetry data, it was established that membranes modified with a Langmuir - Blodgett monolayer of perfluorooctadecanoic acid can be used for the analysis of lead cations in the maximum per-missible concentration region (LOD = 30 μg/l), polyethylene terephthalate track-etched membrane / per-fluorooctadecanoic acid / dimethylglyoxime in a linear concentration range from 2.26 to 15 µg/l. Flexible electrochemical sensors do not change characteristics within 5 measurements.