## 1 Introduction  
Modern proteomic and biosensor systems (including chromato-mass-spectrometric and atomic force microscopy (AFM)-based ones, nanowire biosensors, etc.) allow one to detect proteins in water and water solutions with an ultra-high (\(10^{-18}\) to \(10^{-15}\) M) concentration sensitivity [1; 2; 3; 4; 5; 6]. As a rule, in such systems, polymeric communications and various pumps are employed to supply the solutions to be analyzed. In the supply systems, the liquid flow rate varies over a wide range. So, in chromatography systems employing standard columns (for instance, with an i.d. of 4.6 mm), combined with registration sensor systems, the fluid flow rate is within 0.1 to 10 mL/min [7]. In systems for AFM-based fishing, this rate can be of the order of 1 mL/min [8]. The liquid supply can be organized with an even higher flow rate to provide the efficient delivery of the target analyte molecules to the sensitive area of the sensor chip: for instance, in a nanowire system, this rate can achieve tens of milliliters per minute [6]. In analytical systems based on AFM and nanowire detectors, the liquid is supplied into the measuring cell with an injector represented by a plastic tip for an automatic pipette. As was discussed in the literature, upon the motion of a liquid along a solid surface, a charge separation occurs due to a triboelectric effect; this effect was considered in many papers [9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26]. In the literature, triboelectric phenomena or an electric charge transfer between two materials during friction is commonly described from the viewpoint of physicochemical processes. In this way, to describe the liquid flow electrification, in the paper by [PERSON] et al. [24], the authors discussed the formation of a double electric layer in a liquid, flowing through pipes, owing to the interaction of ions (present in the liquid) with atoms of the pipes'walls [25]. After solving a system of equations describing association/dissociation in the liquid and desorption from/adsorption onto the solid surface, the authors dwelled an equation expressing the wall current density; the latter is proportional to the difference between the charge density in the diffusion layer and wall space charge density. In the paper by [PERSON] et al. [26], the authors demonstrated that the voltage, occurring upon pumping of water through a plastic pipe with a pump, was linearly dependent on the flow rate. In the same paper, it was theoretically justified that the current, occurring upon the liquid flow, is proportional to the pressure gradient, and is connected with hydromechanical parameters (including the pipe length). Micropipette tips are often used in bioanalytical devices for the injection of biological samples into a measuring cell. In these injectors, a generation of charge is also observed. It is caused by triboelectric effects, as discussed in [27]. In this way, [PERSON] et al. [27] discussed several mechanisms of charge generation, occurring upon the flowing of a liquid through a plastic pipette tip. One of these mechanisms is found in the accumulation of static charge on the tip nozzle before the aspiration of the liquid. The electrization of the inner surface of the pipette tip during the contact of its ionized surface groups with water is assumed to be another possible source of charge. In [27], the electrization of a liquid upon its injection is mainly caused by the ionization of surface chemical groups of the pipette tip. In the paper by [PERSON] et al., the influence of air humidity on charge generation was also studied. A relatively weak dependence of the generation of charge in a liquid drop on the air humidity was shown. At the same time, the amount of charge carried by the drop was shown to be dependent on the coating material of the pipette tip.