Ophthalmic Injector Membrane Filtration for Clean Gas-Fluid Switching
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Solution Overview
Problem
Existing injectors for ophthalmic applications require active user intervention for valve actuation, lack indication for fluid delivery timing, and result in uncontrolled mixing of residual fluid with therapeutic agents, affecting delivery composition.
Innovation Solution
An injector with a gas supply tube and liquid supply tube interconnected at a junction, featuring a selective flow member that allows bidirectional gas flow and blocks liquid, forming a controlled liquid buffer to prevent gas delivery during liquid injection, using a PTFE membrane with 0.2-1.0 μm pores for hydrophobic filtration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a valve assembly with actuation arms is used to control fluid flow, then the ability to block bleb fluid during injection is improved, but the requirement for active user intervention and the risk of delays in actuation worsen
Solution Approach 1:
The hydrophobic membrane automatically distinguishes between gas and liquid phases, allowing gas to pass through while blocking liquid without requiring any user intervention. The system serves itself by utilizing the inherent properties of the membrane material to perform the flow control function that previously required manual valve actuation.
Solution Approach 2:
The mechanical valve assembly with actuation arms is replaced by a passive hydrophobic membrane that relies on surface tension and wettability properties rather than mechanical actuation. This substitution eliminates the need for complex mechanical components and user intervention while maintaining reliable flow control.
2Device complexity
If transparent fluids are used in the ducts, then the delivery system is simple, but the lack of indication for fluid delivery timing worsens
Solution Approach 1:
The patent introduces a visual indication mechanism that changes or becomes visible during fluid delivery. While the main fluids remain transparent, the system provides timing indication through visible cues such as the formation of a liquid buffer behind the hydrophobic membrane or other visual signals that indicate when delivery is occurring, thus compensating for the transparency of the fluids.
3Device complexity
If residual fluid remains in the injector downstream of the valve, then the injector structure is simple, but the mixing of residual fluid with therapeutic agent worsens delivery composition control
Solution Approach 1:
The hydrophobic membrane is positioned to create a liquid buffer zone that physically separates and isolates the residual liquid from the incoming therapeutic agent. By extracting or removing the mixing problem through spatial separation, the system prevents contamination while maintaining a relatively simple injector structure without requiring complex flushing or clearing mechanisms.
4Reliability
If a selective flow member is placed in the gas supply tube to block liquid, then prevention of gas delivery during liquid injection is improved, but the volume of liquid buffer that needs to be removed prior to gas delivery worsens switching time
Solution Approach 1:
The hydrophobic membrane's pore size is carefully selected to be small enough to block liquid via surface tension effects but large enough to allow gas molecules to pass through. This parameter optimization ensures that the liquid buffer volume is minimized while still providing reliable liquid blocking, thus reducing the time required to clear the buffer before gas delivery can resume.
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
Enables quick and safe delivery of gas and fluid to the eye with controlled intraocular pressure, minimizing fluid mixing and ensuring clean air irrigation by passive buffer formation and pressure control.
Implementation Method 1
a selective flow member consisting of a membrane comprising polytetrafluoroethylene, PTFE, the membrane having a maximum pore size between 0.2 and 1.0 μm
Implementation Method 2
The selective flow member made of PTFE forms a highly hydrophobic membrane that is sufficiently porous in order to provide for a passage of gas, while blocking a flow of liquid
Implementation Method 3
Liquid is blocked by the selective flow member, forming a liquid buffer of a small volume in the gas supply tube
Implementation Method 4
The membrane further provides for bacterial retention, by blocking bacteria's with a size above the maximum pore size
Data Source
AI summary
Injector for use in ophthalmic applications, having a gas supply tube and a liquid supply tube, both supply tubes being interconnected at a junction member that is in fluid communication with an outflow cannula, characterised in that a selective flow member is placed in the gas supply tube, near the junction member, allowing gases to pass through and blocking the passage of liquid.