Preparation of PEM Based Thin Films using Ultrasonic Spraying
Application of Ultrasonic Spraying Technology in the Preparation of Thin Films on Proton Exchange Membrane Substrates
In electrochemical energy conversion devices such as fuel cells and water electrolysis for hydrogen production, the proton exchange membrane (PEM) serves as a core component. The uniformity and adhesion strength of its surface thin film directly affect the performance and service life of the device. During the fabrication of catalyst-coated membranes (CCM) and membrane electrode assemblies (MEA), achieving high-quality, highly consistent thin coatings on PEM substrates has long been a key challenge in manufacturing processes. Thanks to its unique atomization mechanism and gentle deposition mode, ultrasonic spraying technology has become a highly favored film preparation method in this field.
The basic principle of ultrasonic spraying is to use a piezoelectric transducer to generate high-frequency mechanical vibration, which is amplified by a horn and transmitted to the tip of the nozzle. This causes the liquid to form intense capillary waves at ultrasonic frequencies. When the vibration amplitude is sufficient, droplets overcome surface tension and eject from the nozzle tip, forming fine and uniform mist microdroplets. Unlike traditional pneumatic atomization, ultrasonic atomization does not rely on high-speed airflow to shear the liquid, resulting in a narrower droplet size distribution—typically between 10 and 50 micrometers—with extremely low kinetic energy. The droplets are carried to the surface of the PEM substrate by an auxiliary carrier gas (such as nitrogen or purified air) in a nearly floating manner, rather than being “impacted” onto the substrate at high speed. This “soft landing” characteristic enables ultrasonic spraying to non-destructively deposit functional coatings on proton exchange membranes that are only tens of micrometers thick, soft, and temperature-sensitive.
Directly coating slurries containing precious metal catalysts such as platinum, iridium, and ruthenium onto the PEM surface is a core step in CCM preparation. Traditional methods like blade coating or screen printing tend to scratch or wrinkle the membrane due to mechanical contact, whereas ultrasonic spraying is a completely non-contact process that fundamentally eliminates the risk of substrate damage. More importantly, as the solvent partially evaporates during droplet flight, the slurry reaches the substrate in a concentrated state, which helps suppress the “coffee ring” effect of the coating, thereby forming a catalytic layer with uniform crystallization and reasonable pore distribution. For polymer materials like PEM with relatively low surface energy, ultrasonic spraying achieves a point-by-point drying and layer-by-layer stacking film-forming mechanism through precise control of droplet size (fine droplets are less likely to coalesce into a macroscopic liquid film) and substrate temperature, ultimately producing ultra-flat thin films with thickness controllable from sub-micrometers to tens of micrometers.
The complete construction from CCM to MEA involves not only coating anode and cathode catalytic layers on both sides of the PEM but also laminating diffusion layers and gasket materials. Ultrasonic spraying can also be used to deposit microporous layers or hydrophobic agents (such as polytetrafluoroethylene emulsion) onto gas diffusion layers, but this paper focuses on the direct coating formation on the PEM. In industrial production, PEMs are often processed in a roll-to-roll continuous mode, and ultrasonic spraying systems can be integrated into automated production lines to achieve high-speed, uniform coating of wide-format films through multi-nozzle arrays. With an atomization flow rate as low as 0.1 to several milliliters per minute, it is highly suitable for small-batch, high-value catalyst slurry coating, significantly reducing material waste—especially critical for fuel cell manufacturing where platinum-group metals are expensive.
Another advantage of ultrasonic spraying on PEM substrates is its tolerance to slurry rheology. Ultrasonic atomization operates stably without clogging for both low-viscosity catalyst inks (e.g., alcohol-water mixed systems) and high-viscosity ionomer dispersions. In contrast, piezoelectric inkjet printheads are highly sensitive to slurry particle size and viscosity and prone to nozzle clogging. Ultrasonic nozzles, however, have no tiny orifices and can atomize normally as long as the slurry can flow to the atomizing surface. This provides researchers with great process flexibility when developing new catalyst formulations or optimizing the ratio of ionomer to carbon support.
In summary, for preparing functional films for CCM and MEA on PEM substrates, ultrasonic spraying technology—with its advantages of non-contact, low damage, high uniformity, high material utilization, and strong adaptability to complex slurries—has become an ideal alternative to traditional coating methods. It not only precisely controls the loading and microstructure of the catalytic layer but also protects the fragile PEM substrate from mechanical stress, providing a reliable process route for improving the output performance, durability, and consistency of fuel cells. With the rapid development of the hydrogen energy industry, ultrasonic spraying technology will play an increasingly critical role in the large-scale manufacturing of membrane electrodes.
About Cheersonic
Cheersonic is the leading developer and manufacturer of ultrasonic coating systems for applying precise, thin film coatings to protect, strengthen or smooth surfaces on parts and components for the microelectronics/electronics, alternative energy, medical and industrial markets, including specialized glass applications in construction and automotive.
Our coating solutions are environmentally-friendly, efficient and highly reliable, and enable dramatic reductions in overspray, savings in raw material, water and energy usage and provide improved process repeatability, transfer efficiency, high uniformity and reduced emissions.
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