Microbubble MEMS Accelerometer for Contact Lens Eye Tracking
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Solution Overview
Problem
Current contact lenses with sensors face challenges in manufacturing due to the need for containment and pressure-sensing complexities of solid proof masses, and existing MEMS-based position-sensing systems are unsuitable for contact lenses as they require a heat source close to the eye.
Innovation Solution
A MEMS-based position-sensing system using microbubbles as a proof mass in fluid-filled channels, which are sensitive to small accelerations and can be integrated into contact lenses without a heat source, incorporating angular and linear accelerometers with unique channel orientations and sensors for accurate motion tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If solid proof masses are used in MEMS accelerometers, then measurement precision is improved, but device complexity and manufacturing difficulty increase due to containment and pressure-sensing requirements
Solution Approach 1:
The patent replaces solid proof masses with gas-filled bubbles in fluid channels. The bubbles serve as the inertial element that responds to acceleration, eliminating the need for complex solid mass containment structures and pressure sensors. The fluid medium transmits the inertial effects of the bubbles to the channel walls, which can be directly sensed.
Solution Approach 2:
The invention changes the physical state of the proof mass from solid to gaseous (bubble form). This parameter change allows the proof mass to be contained within fluid-filled channels without requiring complex containment structures, as gases can be easily confined in liquid environments and their motion can be detected through fluid-mediated pressure changes on the channel walls.
2Measurement precision
If conventional MEMS position-sensing systems are used, then position tracking capability is achieved, but the system becomes unsuitable for contact lenses due to heat source requirements
Solution Approach 1:
The patent removes the heat-generating components (heated resistive wires used to create bubbles) from the contact lens environment. Instead, bubbles are introduced through alternative methods that do not require heating elements near the eye, such as injecting gas through micro-injectors or forming bubbles during the lens fabrication process.
Solution Approach 2:
The invention replaces the thermal mechanism (heated wires to create bubbles) with a mechanical or chemical alternative. Gas can be introduced through micro-injectors using pressure-driven injection, or bubbles can be formed during polymerization of the contact lens material, eliminating the need for thermal fields near the eye.
3Measurement precision
If micro-bubble based accelerometers are used, then sensitivity to small accelerations is improved, but manufacturing complexity increases compared to solid proof masses
Solution Approach 1:
The patent combines the bubble generation, containment, and sensing functions into a single integrated fluid-filled channel structure. The channels are fabricated as part of the contact lens itself, and bubbles are introduced through the same micro-fluidic pathways, eliminating the need for separate manufacturing steps for each component.
Solution Approach 2:
The fluid-filled channels serve multiple functions: they contain the bubbles, transmit inertial forces from bubble motion to the channel walls, and provide the sensing interface. This multi-functionality reduces the overall number of components and simplifies the manufacturing process compared to systems requiring separate containment structures and pressure sensors.
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 system provides a sensitive and cost-effective means for tracking eye movements, enabling applications in augmented and virtual reality, gaming, and medical therapy, while being safe and comfortable for wear.
Implementation Method 1
the fluid comprises a micro-bubble suspended in the fluid such that it seeks restorative equilibrium at the relative apex of the channel
Implementation Method 2
the channel comprises an element having greater specific gravity than the fluid such that the element seeks restorative equilibrium at the relative nadir of the channel
Implementation Method 3
motion of the inertial element in the fluid, or motion of the one or more elements having a specific gravity greater than the fluid, relative to the fluid during application of an accelerative force
Data Source
AI summary
The subject matter of the disclosure relates generally to a MEMS-based position-sensing system and lenses, for example, contact lenses and intra-ocular lenses, manufactured with the position-sensing system employing one or more angular and/or linear accelerometers and/or pressure transducers and methods for detecting position and motion of an eyeball and/or head utilizing the position-sensing contact lenses.