Behavioral study of selected microorganisms in an aqueous electrohydrodynamic liquid bridge

Abstract

An aqueous electrohydrodynamic (EHD) floating liquid bridge is a unique environment for studying the influence of protonic currents (mA cm−2) in strong DC electric fields (kV cm−1) on the behavior of microorganisms. It forms in between two beakers filled with water when high-voltage is applied to these beakers. We recently discovered that exposure to this bridge has a stimulating effect on Escherichia coli.. In this work we show that the survival is due to a natural Faraday cage effect of the cell wall of these microorganisms using a simple 2D model. We further confirm this hypothesis by measuring and simulating the behavior of Bacillus subtilis subtilis, Neochloris oleoabundans, Saccharomyces cerevisiae and THP-1 monocytes. Their behavior matches the predictions of the model: cells without a natural Faraday cage like algae and monocytes are mostly killed and weakened, whereas yeast and Bacillus subtilis subtilis survive. The effect of the natural Faraday cage is twofold: First, it diverts the current from passing through the cell (and thereby killing it); secondly, because it is protonic it maintains the osmotic pressure in the cell wall, thereby mitigating cytolysis which would normally occur due to the low osmotic pressure of the surrounding medium. The method presented provides the basis for selective disinfection of solutions containing different microorganisms.

Raman spectroscopy and shadowgraph visualization of excess protons in high-voltage electrolysis of pure water

“…Whereas the electric field strength across the bridge has been simulated before [20,27,28], in the present work it was actually measured. The result of this measurement is shown in figure 3.…”

Electrically Induced Liquid–Liquid Phase Transition in a Floating Water Bridge Identified by Refractive Index Variations

“…Whereas, in the needle-plate set-up this transition only happens when the high voltage is turned on (or off) [33], in the water bridge it happens continuously to the water passing the points of highest field gradients, the location of which is at either end of the bridge nearest the rim of each beaker from which the bridge is suspended. Within the beakers themselves the electric field is almost uniform, as has been both measured [45] and simulated before in two [15] and three dimensions [50,51]. Thus, it is reasonable to expect that the topological structures are created at these points.…”

Pyroelectric Tweezers for Handling Liquid Unit Volumes

“…[27] In this case, the mismatch of different medium still represents a limit for the functionality of the manipulation systems, and to overcome this issue, horizontal liquid bridges have been extensively studied from a theoretical point of view, [28] whereas vertical liquid bridges have been very recently explored for transferring liquid volumes in air between two vertically separating flat surfaces. [29,30] In the manipulation context of liquid and micro-objects, an important role has been recently played by the pyroelectric effect (PYT), already exploited for high-resolution inkjet printing and manipulation of polymers. [31][32][33] Herein, we propose, for the first time, a tweezing system based on the PYT for miniaturized actuation, accurate remote locomotion, and lift against the force of gravity of liquids volumes and micro-objects by thermal stimulus.…”