Vibration Analysis and Development of a Submersible Ultrasonic Transducer for an Application in the Inhibitory Activity of Pathogenic Bacteria

Abstract

Development of a new generation of a submersible ultrasonic transducer (SUT) using vibrational analysis aimed for higher efficiency and inhibitory activity of pathogenic bacteria has been presented. The SUT with a dual-stepped shape of front mass and PZT8 transducer working at 50W, 110V, 50 kHz has been examined by the plate counting method. It was found that the SUT could inhibit pathogenic bacteria, e.g., Escherichia coli, Salmonella typhi, Staphylococcus epidermidis, and Staphylococcus aureus. For the vibrational analysis, the results were derived from structural and acoustic simulations using harmonic response analysis (HRA) in ANSYS software. In the structural simulation, the results showed a natural frequency and total deformations both inside and outside of the original SUT corresponding to the results measured by a laser doppler vibrometer. The acoustic simulation, set up as an actual operation at different depths from the water surface, has been applied. The HRA revealed various distributions of acoustic pressure. For further distances away from the SUT, the acoustic pressure decreased. When the SUT has been submerged deeper into the media, the acoustic pressure becomes larger at positions close to the bottom of the tank. This discovery is consistent with power concentration measurement. For the development of the SUT, this research proposed other 5 models as the candidate to be investigated. The results from the acoustic simulation confirmed that the different shapes of the front mass provided different acoustic pressure distributions. The wider head of the front mass in the modified dual-stepped shape generated the highest acoustic pressure and was fully distributed through an all-over cleaning tank. Therefore, this proposed model is suitable for industrial commercialization and possesses the inhibitory activity of pathogenic bacteria.INDEX TERMS Acoustic pressure, finite element method, harmonic response analysis, pathogenic bacteria, piezoelectric transducer, ultrasonic cleaning, vibration analysis.

Harmonic Response Analysis of Tank Design Effect on Ultrasonic Cleaning Process

“…The HRA is a linear dynamic analysis employed to determine the reaction of materials responding to sinusoidal wave loads in the steady state. Recently, it has been widely applied in developing the UCTs [8,9,[12][13][14][15] and is briefly described in this section.…”

“…The HRA can be calculated in ANSYS software by dividing domains of the UCT materials into interfaces, water, PZT4, aluminum alloy, stainless steel, and tank body [9,14,15], as shown in Figure 1. However, the division is that equations governing the domains are different.…”

“…The bubble size can be estimated from the ω. The higher the value of ω, the smaller the cavitating bubble size [9,18]. For the most efficient cleaning, the bubble size should be close to the size of the contaminant and dirt.…”

“…Furthermore, since the transducer consists of front mass, piezoelectric (PZT) material, and back mass, the PZT is also studied and developed for many purposes [7]. As a result, HRA confirmed that PZT4 provided more intense acoustic pressure than PZT8 [8,9].…”

“…Still, the HRA can report the results at all frequencies, does not require boundary conditions from external sources, and is easy to use. Therefore, most of the recent research prefers to use the HRA to help design and develop ultrasonic cleaning technology [8,9,[12][13][14][15].…”