Ultrasonic antibacterial coating spraying technology: principle, application and prospect

Ultrasonic antibacterial coating spraying technology: principle, application and prospect

With the increasing attention paid to health and safety around the world, antibacterial coating technology is increasingly being used in the fields of medical treatment, food packaging, public facilities, etc. Ultrasonic spraying technology, as an efficient and uniform coating preparation method, is widely used in the preparation of antibacterial coatings. Ultrasonic spraying is a spraying method based on ultrasonic atomization nozzle technology. Compared with traditional pneumatic two-fluid spraying, ultrasonic atomization spraying can bring higher uniformity, thinner coating thickness and higher precision. At the same time, since the ultrasonic nozzle does not require air pressure assistance for atomization, ultrasonic spraying can greatly reduce the paint splashing caused by the spraying process, thereby greatly reducing the waste of paint. The paint utilization rate of ultrasonic spraying is more than 4 times that of traditional two-fluid spraying. This article will introduce the principles, advantages, application fields and future development prospects of ultrasonic antibacterial coating spraying.

Ultrasonic nozzle is a spray nozzle that uses the high-frequency vibration generated by a piezoelectric transducer to act on the nozzle head, thereby generating capillary waves in the liquid film. Once the amplitude of the capillary waves reaches a critical height (due to the power level provided by the generator), they become too high to support themselves, and tiny droplets fall from the tip of each wave, resulting in atomization.

The main factors affecting the initial droplet size are the vibration frequency, surface tension, and liquid viscosity. Frequencies are typically in the range of 20–180 kHz, which is beyond the human hearing range, and within this range, the highest frequencies produce the smallest droplet sizes.

The working principle of ultrasonic nozzles is to use ultrasonic transducers to convert high-frequency sound waves into mechanical energy, which is then converted into liquid to produce standing waves. When the liquid leaves the atomizing surface of the nozzle, it breaks into a fine mist of uniform micron-sized droplets. Unlike traditional nozzles that rely on pressure and high-speed motion to break liquids into small particles. Ultrasonic nozzles use liquid ultrasonic atomization, and the ultrasonic vibration energy is low. The liquid can be delivered to the nozzle by deadweight or a low-pressure liquid pump for continuous or intermittent atomization.

Compared with traditional spraying techniques (such as air spraying and electrostatic spraying), ultrasonic spraying has the following advantages:

Uniform coating: small droplet size (10–50 μm), more uniform distribution, and less material waste.
High efficiency and energy saving: no high-pressure gas requirement, low energy consumption, suitable for precision coating.
Applicable to a variety of materials: solutions containing antimicrobial agents such as nanosilver, titanium dioxide, and quaternary ammonium salts can be sprayed.

No clogging nozzle: no high-pressure spraying, reducing nozzle wear and clogging problems.

Ultrasonic spraying antibacterial coatings usually contain the following active ingredients:
Nanosilver (AgNPs): broad-spectrum antibacterial, destroys bacterial cell membranes.
Titanium dioxide (TiO₂): photocatalytic antibacterial, degrades organic matter under ultraviolet light.
Quaternary ammonium salts (QACs): positively charged, adsorb and destroy microbial cells.
Chitosan: natural antibacterial agent with good biocompatibility.

Application areas
1. Medical equipment and instruments
Spray antibacterial layers on the surfaces of surgical instruments, catheters, masks, etc. to reduce the risk of hospital infection.
Coating of orthopedic implants to prevent postoperative bacterial infection.
2. Food packaging
Spray antibacterial agents on the inner wall of plastic wrap and packaging boxes to extend the shelf life of food.
3. Public facilities
Antibacterial treatment of high-frequency contact surfaces such as elevator buttons, door handles, and public transportation seats.
4. Textiles
Antibacterial coating treatment of medical protective clothing, antibacterial socks, and sportswear.