PCB Capillary Circuit Switching Using Electrochemical Liquid Metal Control
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Solution Overview
Problem
Reconfigurable RF electronics face limitations in tuning range and device topology due to the use of switched electro-mechanical circuit elements and the introduction of pumps and microfluidic elements with liquid conductors, which increase system complexity and require a closed fluid path.
Innovation Solution
A capillary system integrated into a printed circuit board (PCB) containing a eutectic conductive liquid and an electrolyte, with electrodes at both ends and a control circuit to manage DC voltages, allowing the eutectic conductive liquid to form electrical connections between conductive layers and control the tuning of RF components, such as antennas, by extending or retracting the liquid within the capillary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If liquid conductors are pneumatically actuated via pumps or contact pressure to change RF current paths, then the tuning range of the devices is enhanced, but the system complexity increases and a closed fluid path is required
Solution Approach 1:
The patent extracts and eliminates the pump and microfluidic elements from the liquid conductor system. Instead of using pneumatic actuation, the invention uses electrochemically controlled capillarity where electrolyte solution moves in and out of the capillary to control the liquid metal conductor, thereby reducing system complexity while maintaining tuning range.
Solution Approach 2:
The patent replaces the mechanical pneumatic actuation system with an electrochemical system. By applying voltage to the electrolyte solution in the capillary, the liquid metal conductor is moved or retracted through electrocapillary effects, eliminating the need for mechanical pumps and reducing system complexity.
2Ease of operation
If liquid conductors are used in reconfigurable microwave components, then the control over conductor length and location is enhanced, but the introduction of pumps and microfluidic elements adds to system complexity
Solution Approach 1:
The patent implements self-service by allowing the electrolyte solution to autonomously move in and out of the capillary in response to applied voltage, without requiring external pumps or complex microfluidic control systems. The electrocapillary effects naturally drive the liquid metal conductor to the desired positions, maintaining ease of operation while reducing system complexity.
3Adaptability or versatility
If eutectic gallium indium is used as a liquid conductor, then reconfigurable electronics can be achieved at room temperature, but oxidation reactions with air form surface oxide that can stick to surfaces
Solution Approach 1:
The patent introduces an electrolyte solution as an intermediary between the eutectic gallium indium liquid metal and the air environment. The electrolyte fills the capillary and prevents direct contact between the liquid metal and air, thereby preventing oxidation reactions while allowing the liquid metal to be moved and reconfigured through electrocapillary effects.
Solution Approach 2:
The electrolyte solution creates an inert environment around the eutectic gallium indium liquid metal conductor within the capillary. This protective environment prevents oxidation by excluding air from contacting the liquid metal surface, eliminating the harmful adhesion effect while maintaining the reconfigurable electronics capability.
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 efficient tuning of RF components over a wide range of frequencies, reducing system complexity and allowing for versatile reconfiguration of RF properties without the need for pumps or closed fluid paths, while preventing oxidation-induced issues through electrolyte use.
Implementation Method 1
Electrochemically controlled capillarity to dynamically connect portions of an electrical circuit
Implementation Method 2
injecting a eutectic conductive liquid and an electrolyte into an aperture where at least one of the eutectic conductive liquid and the electrolyte contacts a second portion of the at least one electrode
Implementation Method 3
Although EGaIn reacts with air to form a surface oxide that can stick to surfaces including the inner walls of capillaries, this adhesion can be avoided by injecting the metal into capillaries pre-filled with electrolyte. The electrolyte forms a slip layer between the oxide and the walls of the capillary.
Data Source
AI summary
Embodiments herein describe a capillary containing a eutectic conductive liquid (e.g., EGaIn) and an electrolyte (e.g., NaOH) that is integrated into a printed circuit board (PCB). In one embodiment, the PCB includes a capillary, a negative electrode, a positive electrode, a plurality of insulation layers, and a conductive layer. The capillary extends through the PCB. The capillary includes a side surface forming an annular cylinder. A eutectic conductive liquid and an electrolyte are disposed within an aperture formed by the side surface. An electrode extends through the side surface and contacts at least the eutectic conductive liquid or the electrolyte. The negative electrode is disposed at a first end of the capillary. The positive electrode is disposed at a second end of the capillary. The conductive layer is disposed between two of the plurality of insulation layers. The electrode forms an electrical connection with the conductive layer.