Electrocapillary Microfluidic Actuator for Tactile Display Taxels
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Solution Overview
Problem
Current tactile display technologies are unable to create large-scale, high-density actuator arrays with individually addressable actuators that meet the requirements of 1.4 mm spacing, 500 µm height, 100 mN force, bistability, low energy consumption, and affordability, making them unsuitable for portable and cost-effective graphical tactile displays for visually impaired individuals.
Innovation Solution
A fluid shifting device using a microfluidic channel with electrolyte-filled chambers and electrodes to create a capillary valve actuator, which employs electrocapillary forces to control a sealing control element, allowing for bistable operation and low-power consumption, enabling the creation of high-density tactile displays with adjustable taxel heights and greyscale representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional actuators are used for tactile displays, then the required spacing of 1.4 mm and force of 100 mN can be achieved, but the per-actuator cost becomes too high (around 20 € per actuator)
Solution Approach 1:
The device segments the actuator function into separate components: a microfluidic channel structure, a sealing control element (liquid metal plug), and electrode pairs. This segmentation allows each component to be optimized independently and manufactured using low-cost processes like soft lithography and standard PCB fabrication, achieving the required 100 mN force at a cost of only a few Eurocents per actuator.
Solution Approach 2:
The invention replaces conventional mechanical actuators (motors, piezoelectric elements) with a fluid-based actuation system. The sealing control element is moved and positioned using electrocapillary forces generated by electrode pairs, eliminating the need for complex mechanical actuation mechanisms and significantly reducing per-actuator cost while maintaining the required force output.
2Manufacturing precision
If standard actuators are used for tactile displays, then the required resolution and force can be achieved, but the overall display cost becomes prohibitive (around 10.000 € for a Braille line)
Solution Approach 1:
The invention merges multiple functions into a single integrated microfluidic structure: the channel walls serve as both structural elements and electrical insulators, the electrolyte solution provides both ionic conduction and surface tension control, and the liquid metal plug serves as both the sealing element and the actuator. This integration eliminates the need for separate components and assembly steps, reducing the overall display cost to under 1.000 € while maintaining the required 1.4 mm spacing and 500 µm height resolution.
Solution Approach 2:
The invention uses parameter changes in the fluid system to control actuator state. By changing the voltage applied to electrode pairs, the surface tension of the liquid metal plug is modified, causing it to move between chambers and change the actuator from raised to flat state. This parameter-based control allows for precise resolution (500 µm height) using simple voltage control, achieving high manufacturing precision at low cost.
3Use of energy by moving object
If non-bistable actuators are used for tactile displays, then continuous control is possible, but power consumption increases and refresh rates become too slow for portable applications
Solution Approach 1:
The actuator system is self-latching through the physical confinement of the liquid metal plug within chambers. Once the plug moves to a chamber, it remains there without requiring continuous power, as the chamber geometry and surface tension forces maintain the position. This self-service mechanism provides inherent bistability (raised/f flat states) with zero standby power consumption, enabling portable tactile displays with refresh rates faster than 10 seconds while maintaining stable actuator states.
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
The solution enables the development of portable, cost-effective tactile displays with high-density actuator arrays that can represent graphical content, meeting the necessary resolution and force requirements while minimizing energy consumption, thus addressing the limitations of existing technologies.
Implementation Method 1
at least one pair of electrodes arranged such that the electrodes are in fluidic contact with the at least one chamber for causing, in response to the control signal, an electrocapillary force acting on the sealing control element
Implementation Method 2
the sealing control element has a surface tension which is higher than a surface tension of the fluid, such that in the absence of the control signal at least a portion of the sealing control element is trapped in one of the at least one chamber due to an intrinsic capillary force
Implementation Method 3
the sealing control element has a surface tension which is higher than a surface tension of the fluid
Data Source
Figure 1a~1c
Figure 2a~2e
Figure 3
AI summary
The present invention relates to a device and method for shifting a fluid within a fluid channel. The device comprising: - a fluid channel (20) comprising at least one chamber (15), each chamber (15) being filled with a fluid (12) comprising an electrolyte and having at least two inlets (17); - a sealing control element (13) being enclosed in the fluid (12) of the fluid channel (20) for sealing the at least one chamber (15) and controlling a shift of the fluid (12) within the fluid channel (20) in response to a control signal (30); and - at least one pair of electrodes (8) arranged such that the electrodes (8) are in fluidic contact with the at least one chamber (15) for causing, in response to the control signal (30), an electrocapillary force acting on the sealing control element (13); wherein the sealing control element (13) has a surface tension which is higher than a surface tension of the fluid (12), such that in the absence of the control signal (30) at least a portion of the sealing control element (13) is trapped in one of the at least one chamber (15) due to an intrinsic capillary force, thereby sealing said one of the at least one chamber (15).