## 1 Introduction  
One of the problems of further development of proteomics and medical diagnostics is to increase the sensitivity of protein registration methods. This is particularly important in the case of early diagnosis of diseases (including oncological and viral ones), when the analysis sensitivity must be at the level of femtomolar concentrations, corresponding to the concentrations of disease-associated marker proteins [1]. Nanobiosensor systems for proteomics and medical diagnostics, such as those employing atomic force microscope (AFM)-based fishing and nanowire detectors (i.e., the systems, in which molecular detectors are employed), allow one to register single viral particles and protein molecules with ultra-high sensitivity in counting mode [2; 3; 4; 5]. These systems use an approach based on the introduction of an aqueous solution of an analyte (protein or virus) through an injector using either a pipette or flow system into a measuring cell containing a nanochip; analyte particles are captured onto the nanochip surface (i.e., fishing of the analyte occurs), where they are registered with molecular detectors in counting mode. In our previous paper [6] it was reported that by using systems for AFM-based fishing (that is, the systems, in which protein particles are captured from a large volume onto a small area of a chip for an atomic force microscope) it is possible to detect proteins at femtomolar and subfemtomolar concentrations upon feeding the protein solution into the measuring cell using an injector. As one of the factors of such a high efficiency of protein detection, the effect of charge generation in the analyte solution during its flow through an injector is considered. It is known that an electric charge is generated during the injection of a solution through a pipette tip [7]. At the same time, according to Reference [2], in a nanobiosensor system for AFM-based fishing at femtomolar and subfemtomolar protein concentrations, we observed a tendency for it to increase the number of captured protein molecules with the increase in the charge generated upon injection of analyzed solution into a measuring cell. External pulsed voltage applied to the measuring cell, was previously used by us to induce electric fields in flow-based systems for AFM-based fishing in order to enhance their sensitivity (up to the subfemtomolar level), as was demonstrated in Reference [6]. Thus, to enhance the efficiency of protein capturing in an AFM-based fishing system, it is important to study the phenomenon of charge generation during the flow of an aqueous solution through a flow-based system in various conditions. It is to be noted that the generation of charge during the flow of water and aqueous solutions along various surfaces [8], as well as changes in the physicochemical properties of water upon its flowing through polymer injectors [9], were long and widely discussed in the literature. In our previous paper [10], we demonstrated that negative pulsed voltage applied to parallel metal plates, between which an injector of the AFM-based fishing system was located, led to an increase in the efficiency of charge generation in the injector. At the same time, we demonstrated that an external AC electric field (with 50 Hz mains frequency, which is often present in biosensor devices) caused an increase in efficiency of charge generation in water flowing through an injector at a low-grade fever temperature (38 \({}^{\circ}\)C) [11]; this temperature is higher than that of phase transition of water related with heat capacity (36.6 \({}^{\circ}\)C, [9]) and corresponds to a pathology in human. Attention to the effect of materials, which are not directly contacting with flowing aqueous solutions, is usually given from the viewpoint of controlling the charge generation in a flowing solution with an external electric field.