Azimuthally Oscillating Membrane Emulsification for Droplet Control
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Solution Overview
Problem
Conventional membrane emulsification systems face limitations in producing large droplets with uniform size distribution due to high shear stress and recirculation issues, leading to droplet damage and poor control over droplet size, especially when aiming for droplets above 10 μm in diameter.
Innovation Solution
An azimuthally oscillating cylindrical membrane system is introduced, where the membrane oscillates backwards and forwards, allowing control of shear stress through frequency and displacement rather than rotation speed, decoupling droplet size control from continuous phase flow, and using a hydrophobic coating to prevent membrane wetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fully rotating membrane system is used to generate shear stress for droplet detachment, then droplet production is achieved, but centrifugal field induces flow of oil drops toward the membrane surface leading to increased coalescence and membrane wetting
Solution Approach 1:
The patent transitions from a stationary or fully rotating membrane to an azimuthally oscillating membrane that periodically moves back and forth. This dynamic oscillation generates variable shear stress at the membrane surface without creating a sustained centrifugal field, thereby preventing oil drops from migrating toward the membrane surface and reducing coalescence and wetting issues.
Solution Approach 2:
The membrane is oscillated azimuthally with a specific frequency and amplitude, creating periodic shear stress variations. This periodic action allows for controlled droplet detachment while avoiding the continuous centrifugal force present in fully rotating systems, thus preventing harmful accumulation of oil drops at the membrane surface.
2Manufacturing precision
If high shear stress is applied to produce smaller droplets, then droplet size is reduced, but dispersed phase concentration decreases requiring recirculation which damages droplets
Solution Approach 1:
The patent changes the control parameters from rotation speed to oscillation frequency and amplitude. By adjusting these parameters, the system can generate appropriate shear stress for desired droplet sizes without requiring high continuous phase flow rates, thus achieving high dispersed phase concentrations in a single pass without recirculation.
Solution Approach 2:
The oscillating membrane creates time-varying shear stress that is highly effective at the membrane surface where droplet formation occurs. This dynamic shear generation allows for efficient droplet detachment and size control without needing high bulk flow rates that would dilute the dispersed phase concentration.
3Manufacturing precision
If crossflow rate is increased to provide higher shear stress for smaller droplets, then droplet size is reduced, but dispersed phase concentration decreases
Solution Approach 1:
Instead of relying on high crossflow rates to generate shear stress, the patent uses an oscillating membrane to create localized dynamic shear at the membrane surface. This approach generates sufficient shear for small droplet formation without increasing bulk flow rate, thus maintaining high dispersed phase concentration.
Solution Approach 2:
The oscillation creates highly localized shear stress concentrated at the membrane surface where droplet formation occurs, rather than distributing shear throughout the bulk flow. This localized quality of shear generation achieves effective droplet size control without requiring high overall flow rates that would reduce dispersed phase concentration.
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 system achieves high dispersed phase concentrations up to 38% v/v in a single pass without recirculation, with droplet sizes ranging from 20-120 μm and a coefficient of variation of 8%, providing consistent and reproducible results suitable for industrial applications like chromatography and drug carriers.
Implementation Method 1
shear stress at the membrane surface using a force balance
Implementation Method 2
azimuthally (tangentially) oscillated with frequencies of, for example, up to 50 Hz and displacement of, for example, 7 mm
Implementation Method 3
using a hydrophobic coating to prevent membrane wetting
Implementation Method 4
a membrane defining a plurality of apertures connecting a first phase on a first side of the membrane to a second phase on a second different side of the membrane, such that egression of the first phase into the second phase via the plurality of apertures creates an emulsion
Data Source
AI summary
An apparatus for membrane emulsification. In one embodiment, the apparatus comprises a membrane defining a plurality of apertures connecting a first phase on a first side of the membrane to a second phase on a second, different side of the membrane, such that egression of the first phase into the second phase via the plurality of apertures creates an emulsion, and wherein the membrane is an oscillating cylindrical membrane.