As demand grows for compact and precise drug-delivery technologies, piezoelectric mesh atomizers are emerging as an important component in next-generation nebulisers and inhalation devices. However, the laser-drilling processes used to create micron-scale holes in atomiser meshes can introduce recast material and microscopic metal debris, raising concerns around particulate cleanliness, aerosol consistency and device reliability.
Piezo Direct is addressing this challenge through a proprietary post-processing technology designed to remove recast metal and sub-micron debris while preserving the geometry of the micro-holes. The company manufactures mesh atomisers with laser-drilled holes as small as 2.0 microns, enabling device developers to engineer aerosol characteristics for specific inhalation applications.
In this interview with MedTech Spectrum, Li Hsu, CEO of Piezo Direct, discusses the limitations of conventional laser-drilled mesh atomisers, the company's approach to post-processing and particulate control, and how micron-scale hole geometry influences aerosol performance. He also outlines Piezo Direct's quality-control processes, potential applications in inhaled drug delivery, and its roadmap towards smaller micro-holes, improved materials and automated inspection.
What are the key limitations of conventional mesh-based piezo atomizers used in nebulizers and inhalation devices, particularly regarding particulate contamination from laser drilling?
Mesh-based piezo atomizers rely on an array of extremely small, precisely formed holes to convert a liquid formulation into an aerosol. Laser drilling is an effective method for producing these micro-holes, but the process can leave recast material around the hole openings as well as very small metallic debris on or near the mesh surface.
This is particularly important in inhalation applications because the aerosol generated by the atomizer is delivered directly into the patient's respiratory system. Consequently, particulate cleanliness of the mesh is a much more significant consideration than it may be in many non-medical atomization applications.
Residual recast material can also affect the functional performance of the mesh. Variations or contamination around the micro-holes may contribute to inconsistent flow, changes in aerosol characteristics, or partial blockage of individual holes. For medical applications requiring repeatable aerosol delivery, maintaining both the geometry and cleanliness of the micro-hole array is therefore important.
Could you explain how Piezo Direct’s post-processing technology removes the recast metal lip and sub-micron-sized debris without altering the micro-hole geometry or compromising the base material?
Piezo Direct has developed a proprietary post-processing method using specialized, purpose-built equipment to clean the mesh after the laser-drilling process.
The objective is to remove recast material and residual microscopic debris generated during laser drilling while preserving the geometry of the micro-holes and the integrity of the underlying mesh material. This is especially challenging as hole diameters approach only a few microns, where even a very small amount of residual material can become significant relative to the dimensions of the hole itself.
The exact process parameters and equipment configuration are proprietary, so we cannot disclose the details. However, the process has been specifically developed to provide a high level of cleanliness without materially changing the micro-hole geometry that determines the atomizer's performance.
How does your micro-hole technology, with laser-drilled holes as small as 2.0 microns, influence aerosol generation, droplet size, and overall atomization performance?
Micro-hole diameter is one of the important parameters affecting aerosol particle-size distribution. Piezo Direct currently manufactures mesh atomizers with laser-drilled holes down to approximately 2.0 microns.
In one of our 16 mm mesh atomizer configurations, a nominal 2.0-micron micro-hole design produces an MMAD (mass median aerodynamic diameter) of approximately 2.0–2.1 microns under the specified operating conditions.
It is important to emphasize that hole diameter alone does not determine final aerosol performance. MMAD and output characteristics are also influenced by factors including micro-hole geometry, number and distribution of holes, mesh structure, resonant frequency, vibration amplitude, drive conditions, and the physical properties of the liquid formulation.
This ability to engineer the mesh geometry provides device designers with another means of optimizing aerosol particle size, output rate, and delivery characteristics for a particular application.
What testing or quality-control processes does Piezo Direct use to verify particulate cleanliness for applications where the generated mist is directly inhaled by patients?
Particulate control begins with the manufacturing process rather than relying solely on inspection of the finished component.
Our approach includes controlled production processes, manufacturing in a clean environment, microscopic/electron-microscope visual inspection of the mesh and micro-hole area, and batch-to-batch consistency testing. These controls are intended to verify both the cleanliness of the mesh and the consistency of the micro-hole structure.
For inhalation applications, we recognize that cleanliness requirements are particularly important because the aerosol may be delivered directly to the respiratory tract. We therefore focus on controlling potential contamination at the manufacturing stage and verifying consistency throughout production.
We are also developing increased automation in our inspection processes to move toward 100 per cent inspection of production components.
What potential applications do you foresee across medical devices, and how does improved mesh cleanliness contribute to overall device safety and performance?
We see significant potential in high-precision inhaled-drug-delivery devices, including portable nebulization systems and other applications requiring controlled generation of fine aerosols.
For these devices, improved mesh cleanliness contributes not only to contamination control but also to functional consistency. A cleaner, more uniform micro-hole array can help maintain stable atomization output, reduce batch-to-batch variation, and support the repeatable delivery characteristics required in medical-device applications.
Reducing residual material around the micro-holes can also reduce the possibility of unintended hole blockage during operation. This can improve the useful life and reliability of the mesh and help maintain more consistent atomization performance over time.
Ultimately, the mesh is one component within the complete drug-delivery system, and final device safety, dose accuracy, and regulatory compliance must be validated by the medical-device manufacturer at the system level.
What are the next steps for Piezo Direct regarding regulatory approvals, commercial deployment, and further development of this technology?
Piezo Direct's role is primarily as a component and technology supplier to medical-device developers and manufacturers. Regulatory approval generally applies to the finished medical device and its intended use rather than to the mesh atomizer component in isolation. We therefore work with customers to provide the component performance, manufacturing consistency, and technical support needed for integration into their devices and validation programs.
From a technology-development standpoint, we are continuing to work in three principal areas.
First, we are developing even smaller micro-hole diameters to enable further control over aerosol characteristics.
Second, we are evaluating improved diaphragm and mesh materials to achieve better overall atomization performance, durability, and reliability.
Third, we are increasing automation of our quality-control and inspection processes. Our development objective is an automated inspection system capable of 100 per cent inspection of production meshes rather than relying only on sampling.
We believe these improvements—smaller and more precisely controlled micro-holes, improved diaphragm materials, advanced post-processing, and automated inspection—will help support the next generation of high-precision inhalation and drug-delivery devices.
