Electrowetting Membrane for Variable Pore Surface Control
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Solution Overview
Problem
In microfluidic systems, membranes often impede the transport of liquids due to wetting behavior, requiring high pressures or pressure differences that may not be feasible or lead to uncontrolled liquid transport, and can result in residual liquids remaining on the membrane.
Innovation Solution
A fluidic system with electrodes that apply an electrical field to the membrane, changing the contact angle between the pore surface and the interface, allowing for reversible manipulation of surface energy to control the wetting behavior and reduce the pressure required for liquid transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high pressure or pressure difference is applied to overcome wetting behavior, then liquid transport through the membrane is achieved, but mechanical stress on the membrane increases and uncontrolled liquid transport may occur
Solution Approach 1:
The patent changes the wetting parameter (contact angle) of the membrane surface by applying an electrical field, which modifies the surface energy of the membrane. This parameter change allows the membrane to transition from a wetting state (high contact angle) that resists liquid transport to a non-wetting state (low contact angle) that facilitates liquid passage, thereby reducing the pressure required for transport.
Solution Approach 2:
The patent replaces the purely mechanical approach (applying high pressure to overcome wetting) with an electrostatic approach. By applying an electrical field to modify the contact angle, the system uses electrical energy to control wetting behavior, substituting mechanical stress with an electromagnetic field-based control mechanism.
2Productivity
If high pressure is used to force liquid through the membrane, then transport is achieved, but residual liquids remain on the membrane
Solution Approach 1:
The patent employs periodic switching of the electrical field to alternately change the contact angle between wetting and non-wetting states. During the non-wetting state, liquid is transported through the membrane; during the wetting state, the membrane surface is cleaned of residual liquids. This periodic action ensures complete liquid transport without residues.
Solution Approach 2:
The patent uses the electrical field to first facilitate liquid transport, then subsequently cleans the membrane surface by switching to a wetting state that draws residual liquids off the membrane. This discards residual liquids that would otherwise remain on the membrane, ensuring complete transport.
3Reliability
If the membrane structure is used to separate media, then geometric separation is achieved, but wetting behavior impedes fluid control
Solution Approach 1:
The patent makes the membrane's wetting properties dynamic by applying an electrical field that can switch the contact angle between different states. This dynamic control allows the membrane to adapt its wetting behavior to operational requirements, enabling precise fluid control while maintaining its geometric separation function.
Solution Approach 2:
The electrical field acts as an intermediary between the control system and the membrane's wetting properties. By applying the electrical field, the system indirectly controls the contact angle and wetting behavior, providing a means to manipulate fluid control without directly altering the membrane's physical structure.
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 reliable fluid control by reducing the pressure needed for liquid transport through the membrane, preventing residual liquids and minimizing mechanical stress on the membrane, thus improving the efficiency and reliability of fluid handling in microfluidic systems.
Implementation Method 1
there being a contact angle between the interface and the pore surface... in a first state Z1 with a first electric field E1, the membrane has a pore surface that is not wetted or wetted less by the first medium... at least one surface energy depends on the electric field and is reversibly changeable
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3C
AI summary
A fluidic system having a first volume, a second volume and a membrane geometrically separating the two volumes, which has an open-pore microstructure for the passage of a first medium and a second medium. There is a contact angle (Θ) between the interface of the media and the pore surface. A first electrical field in the region of the membrane and a first electromagnetic radiation and a first heating of the membrane define a first state (Z1), in which the membrane is not wetted or is less wetted by the first medium and is more heavily wetted by the second medium such that a first contact angle Θ1>90° is formed between the pore surface and the interface. The first medium and the second medium and the pore surface have a surface energy of which at least one surface energy can be reversibly changed in such a way that a second contact angle Θ2<Θ1 occurs between the pore surface and the interface in a second state (Z2).