# Innovative Ultrasonic Spray Methods for Indoor Disinfection
## 2 Development of Ultrasonic and Combined Spraying Devices for Disinfectant Liquids
### High-Capacity Wearable Atomizer Designs for Generating a Variety of Particle Sizes  
Figure 5 shows a device for forming an aerosol with an average particle size of no more than 50 \(\upmu\)m and a capacity of up to 20 mL/s for treating people's clothing, vehicles, and small rooms. To provide an increased spray area, a flexural-oscillating disk (oscillations are carried out on the second mode) with a diameter of 40 mm is used. Using a disk enables a nearly unrestricted increase in the spray surface area by exciting bending oscillations in higher-order modes. In turn, the use of a disk allows for a virtually unlimited increase in the area of the spray surface due to the excitation of bending oscillations at higher modes. This also reduces the disk's thickness, positively impacting the sprayer's mass and size characteristics. In general, the operation of the disk is similar to the oscillations of a membrane with free edges with the central excitation of oscillations. The distribution of oscillations over the surface of such a disk is described by Bessel functions of the corresponding order (equal to the oscillation mode of the disk). The resonant frequency of the sprayer is 40 kHz. Liquid is delivered to the spray surface through 12 holes positioned at the disk's zero-oscillation points. The principle of constructing the oscillating system of the atomizer is similar to that shown in Figure 1.  
As shown in Figure 6, the sprayer includes a pistol-type handle (9). On the handle there is a button (10) for starting the spraying. In this case, electric oscillations of ultrasonic frequency are supplied from the generator to the piezoelectric elements of the sprayer and the sprayed liquid is simultaneously supplied to the spray surface (4), through the channels (6). The electric oscillation generator operates from a 12 V battery and can be placed in a portable backpack behind the operator (together with a volume with a disinfect solution). Figure 5: Ultrasonic wearable atomizer for forming an aerosol with an average particle size of no more than 50 \(\upmu\)m and a capacity of up to 20 mL per second: (**a**) three-dimensional model, (**b**) structural diagram. 1—piezoelectric transducer; 2—booster link; 3—concentrator; 4—flexural–oscillating disk (atomizing surface); 5—internal channel for atomized liquid; 6, 7—internal channels of the atomizing tool; 8—atomizer body; 9—handle; 10—trigger for starting the atomizer; 11—outlet of the power cable combined with the atomized liquid supply tube. Figure 6 shows a high-performance sprayer for forming an aerosol with an average particle size of 65 microns and a capacity of more than 60 mL/s, designed for treating public transport, the metro, and premises. To ensure such a high performance (more than 60 mL/s), the area of the spray surface was significantly increased. Similar to the previous device, it employs a bending-oscillating disk. The diameter of the disk is increased to 250 mm; it oscillates in mode 3. The sprayed liquid is in a backpack container, which is located behind the operator. A liquid supply system (pump and valve) is installed on the liquid container. An electronic generator for powering the ultrasonic sprayer is also installed on the backpack container. The electronic generator operates using high-capacity lithium-ion batteries. Thus, a number of ultrasonic sprayer models have been developed that have good user characteristics--high dispersion, narrow particle-size distribution, and satisfactory performance for various tasks. Their operating principle is based on the excitation of capillary waves in a liquid film using ultrasonic vibrations. In the presented devices, an increase in spray performance is achieved by significantly increasing the area of the spray surface. However, it is not possible to infinitely increase the area of the spray surface. This requires the development of new ultrasonic liquid spraying methods based on a combination of ultrasonic action and other factors.