Hybrid Material Nebuliser Mesh for Tight Nozzle Tolerance
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Solution Overview
Problem
Current nebuliser mesh manufacturing techniques face challenges in achieving tight tolerance on nozzle exit diameter and sufficient mass per unit area while maintaining a low cost and high yield, due to difficulties in achieving precise nozzle exit diameter and density requirements using existing methods like electroformation and laser-drilling.
Innovation Solution
A hybrid mesh geometry is employed, where a dense material provides the necessary mass per unit area and a lower-density material is used to form nozzles with precise exit diameters, utilizing techniques like chemically etching or laser-etching to achieve the required tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electroformation or laser-drilling techniques are used to manufacture the mesh, then the mesh can be produced, but the nozzle exit diameter tolerance cannot be achieved within the required range
Solution Approach 1:
The patent changes the material parameter from traditional metals to silicon, which has different physical and chemical properties that enable precise nozzle formation through chemical etching. This material parameter change allows achieving the required 2.5μm±0.5μm nozzle exit diameter tolerance that was not achievable with electroformation or laser-drilling techniques
Solution Approach 2:
The patent replaces mechanical manufacturing techniques (electroformation, laser-drilling) with a chemical etching process. The chemical etching method uses wet or vapor HF etching to precisely define the nozzle geometry in silicon, achieving the required dimensional precision without the limitations of mechanical or thermal processes
2Reliability
If a dense material is used to provide sufficient mass per unit area, then the resonant cavity requirement is met, but the manufacturing cost increases and yield decreases
Solution Approach 1:
The patent changes the material parameter to silicon, which has a density of 2.33g/cm³. While not as dense as traditional metals, the silicon mesh design achieves the required mass per unit area (0.04g/cm²) through optimized geometry and thickness, meeting the resonant cavity requirement while enabling higher yield manufacturing through chemical etching processes
3Device complexity
If traditional manufacturing techniques are used, then the process is simpler, but the nozzle exit diameter cannot be controlled within the required tolerance range
Solution Approach 1:
The patent replaces complex mechanical and thermal manufacturing processes with a chemical etching process. The chemical etching method provides better control over nozzle exit diameter dimensions and tolerances, achieving 2.5μm±0.5μm precision while actually simplifying the manufacturing workflow by eliminating the need for multiple processing steps and complex equipment
Solution Approach 2:
The patent changes the manufacturing approach from mechanical/thermal processes to chemical etching, utilizing the anisotropic etching characteristics of silicon to precisely define nozzle geometry. This parameter change in the manufacturing method enables superior dimensional control and tolerance achievement
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the production of nebuliser meshes with tight tolerance on nozzle exit diameter and sufficient mass for resonant cavity creation at a lower cost, improving the yield and efficiency of the manufacturing process.
Implementation Method 1
Piezo-mesh based nebulisers (one type of which uses a 'flat plate' geometry of a piezoelectric element and a mesh to produce aerosol) are commonly used to generate aerosols in such drug delivery apparatus, whereby a piezoelectric element vibrates the liquid through a mesh to produce the fine aerosol spray
Implementation Method 2
The actuator is operated to create ultrasonic pressure waves in the liquid 12 which push the liquid 12 through the nozzles in the mesh 16 to form the droplets
Implementation Method 3
The reflected pressure wave helps to increase the pressure further, keeping energy in the system, which results in less energy needing to be input to the liquid by the actuator 14
Data Source
AI summary
There is provided a mesh for use in forming droplets of liquid in a nebuliser, the mesh comprising a first portion (22) made of a first material having a plurality of holes passing therethrough; and a second portion (26) made of a second material that is in contact with the first portion (22), the second portion (26) having a corresponding plurality of holes passing therethrough, the plurality of holes in the second portion forming nozzles (28) for an outlet side of the mesh; wherein the first material has a higher density than the second material.