Application Cases

Experiment Name: Acoustic Study of Ultrasonic Antibacterial Inhibition

Experimental Principle:
Ultrasonic guided waves possess the characteristic of propagating long distances along the surfaces of tubular structures, making them a promising new technology for inhibiting surface bacterial biofilms. This experiment investigates the effects of the excitation frequency and amplitude of ultrasonic guided waves on biofilm inhibition. The surface vibration of the endotracheal tube was measured, and the reasons for the significant attenuation of guided waves on the tube were analyzed. The experimental setup was optimized through the use of coupling agents and adjustments to the incidence angle of the guided waves to enhance the surface vibration amplitude of the endotracheal tube. An experimental setup for inhibiting Pseudomonas aeruginosa biofilms was established to study the inhibitory effects of guided waves with different vibration amplitudes on biofilm formation on the surface of the endotracheal tube.

Figure 1: Diagram of the Guided Wave Antibacterial Experimental Setup

Testing Equipment:
Signal generator, ATA-8202 RF power amplifier, ultrasonic transducer, test tubes, bacterial culture medium, etc.

Experimental Procedure:
This experiment used an adult endotracheal tube for antibacterial testing. During the experiment, the ventilator interface was removed, leaving only the main body of the endotracheal tube, which was inserted into the guided wave coupling mechanism. A frequency of 50 kHz was selected as the excitation frequency for the guided waves. The ATA-8202 power amplifier was used to drive five sets of transducers, each applying different excitation levels to the endotracheal tube. The vibration amplitude on the tube was measured at a distance of 1 cm from the contact point. After performing FFT transformation on the measured waveform signals, the signal amplitudes for the five experimental groups were adjusted to 0 nm, 0.05 nm, 0.5 nm, 5 nm, and 50 nm, respectively. Table 1 provides the descriptions of the five experimental groups. Since there may be consistency differences among the transducers, the surface vibration of the endotracheal tube was measured before applying the excitation.

Table 1: Grouping Scheme for the Guided Wave Biofilm Inhibition Experiment

During the experiment, multiple sets of test tubes were fixed to a test tube stand and placed in a constant-temperature incubator at 37°C with a CO₂ concentration of 5%. Figure 2 illustrates the setup of the multiple test tube experimental stand.

Figure 2: Schematic Diagram of the Multiple Test Tube Experimental Stand

Pseudomonas aeruginosa (P. aeruginosa), the most common bacterium in the human trachea, was used as the experimental subject. The culture medium was Tryptic Soy Broth (TSB), prepared by mixing 15 g of Tryptic Soy Broth powder with 500 ml of water. The mixture was heated to dissolve, distributed into test tubes (4 ml per tube), and sterilized in an autoclave at 121°C for 15 minutes before use. Pseudomonas aeruginosa was inoculated into the Tryptic Soy Broth medium and cultured for 6 hours for enrichment. Then, 10 µl of the bacterial suspension was added to different culture tubes for further bacterial cultivation. The culture tubes were placed in a constant-temperature incubator (37°C, 5% CO₂ concentration).

Experimental Results:
Due to limitations in the number of signal sources, the five experimental groups requiring signal excitation were not conducted simultaneously, and there may be differences in the consistency of bacterial culture. To evaluate these differences, the results of biofilm concentration and bacterial suspension concentration were normalized. Table 2 presents the normalized experimental data for biofilm concentration on the adult endotracheal tube. Figure 3 shows a bar chart comparing the normalized biofilm concentrations in the five groups of adult endotracheal tubes. As observed, the biofilm concentration in all experimental groups increased over time, but this growth trend slowed after 18 hours. In the experimental groups with higher ultrasonic guided wave excitation (0.5 nm), the biofilm on the surface of the endotracheal tube was significantly inhibited. Statistical analysis of the data revealed that as the amplitude of the guided wave excitation increased, the biofilm inhibition effect also strengthened. A comparison between Group 4 (amplitude 5 nm) and Group 5 (amplitude 50 nm) showed that when the amplitude of the excited guided wave exceeded 5 nm, the effect did not change significantly. This indicates that the biofilm inhibition effect is not simply proportional to the vibration amplitude but exhibits a clear positive correlation within a certain amplitude range (0.5 nm–5 nm).

Table 2: Normalized Experimental Data for Biofilm Concentration on the Adult Endotracheal Tube

Figure 3: Comparison Chart of Normalized Biofilm Concentrations on the Adult Endotracheal Tube

The experimental materials in this article were compiled and released by Xi'an Aigtek Electronics. For more experimental solutions, please continue to follow the Aigtek official website.