Online monitoring of biofouling using coaxial stub resonator technique

Abstract

a b s t r a c tHere we demonstrate the proof-of-principle that a coaxial stub resonator can be used to detect early stages of biofilm formation. After promising field tests using a stub resonator with a stainless steel inner conductor as sensitive element, the sensitivity of the system was improved by using a resonator of shorter physical length, implying higher resonance frequencies (and by that a higher frequency range of operation) and improved sensitivity towards dispersion. In addition, the space between inner and outer conductor was filled up with glass beads, thereby exploiting the larger surface area available for biofilm formation.Analysis of the biofilm and the stub resonator signal, both as function of time, indicates that the sensor allows detection of early stages of biofilm formation. In addition, the sensor signal clearly discriminates between the first stages of biofilm formation (characterized by separated, individual spots of bacterial growth on the glass beads) and the presence of a nearly homogeneous biofilm later on in time. Model simulations based on the transmission line theory predict a shift of the sensor response in the same direction and order of magnitude as observed in the biofouling experiments, thereby confirming the operating principle of the sensor.

Antibacterial, Anti‐Biofouling, and Antioxidant Prospects of Metal‐Based Nanomaterials

“…. Biofouling – the condition in which a biofilm is formed on surfaces that come into contact with water – annually costs millions of dollars for the removal of the biofilms or replacement of the affected parts . It is conceivable, therefore, that the antibacterial and anti‐biofouling properties of materials are important considering the growing demand for new, effective, and environmentally friendly antibacterial agents .…”

Characterization of Biofilm Formation and Coating Degradation by Electrochemical Impedance Spectroscopy

“…Resolved nominal biofilm capacitance is shown in Figure 12. With the assumption that the dielectric constant for biofilm is ε ≈ 70 [28], the resolved capacitance for the antifouling and comparative polyurea coating (in the order 10 −4 to 10 −8 F) would result in a calculated film thickness t < 10 −4 mm [29]. The biofilm-associated impedance was typically resolved at day 0 for the polyurea coating and after some days for the commercially available antifouling coating.…”

“…Coatings 2019, 9, x FOR PEER REVIEW 10 of With the assumption that the dielectric constant for biofilm is ε ≈ 70[28], the resolved capacitance for the antifouling and comparative polyurea coating (in the order 10 −4 to 10 −8 F) would result in a calculated film thickness t < 10 −4 mm[29].…”

Resonant coaxial SMA microwave permittivity sensor

“…Another coaxial method used to measure the dielectric properties of fluids is a method based on usage of coaxial open stub λ g /4 (or coaxial shorted λ g /2 ) resonator [5][6][7][8]. This technique is less sensitive to errors, especially for the errors produced by electromagnetic interference.…”

“…In all cases found in [5][6][7][8] the measurement systems are used with relatively high amount of fluids, mainly for water monitoring. In these cases, diameter of open stub is around 25 mm while length over 250 mm.…”